From 08a97a6d193f46cd547fadae3bb4125cc788543b Mon Sep 17 00:00:00 2001
From: Marek Majkowski <marek@cloudflare.com>
Date: Thu, 2 Jan 2020 12:09:24 +0100
Subject: #1398 - send ACK when available buffer space gets larger than 1 MSS

When receiving data, netstack avoids sending spurious acks. When
user does recv() should netstack send ack telling the sender that
the window was increased? It depends. Before this patch, netstack
_will_ send the ack in the case when window was zero or window >>
scale was zero. Basically - when recv space increased from zero.

This is not working right with silly-window-avoidance on the sender
side. Some network stacks refuse to transmit segments, that will fill
the window but are below MSS. Before this patch, this confuses
netstack. On one hand if the window was like 3 bytes, netstack
will _not_ send ack if the window increases. On the other hand
sending party will refuse to transmit 3-byte packet.

This patch changes that, making netstack will send an ACK when
the available buffer size increases to or above 1*MSS. This will
inform other party buffer is large enough, and hopefully uncork it.


Signed-off-by: Marek Majkowski <marek@cloudflare.com>
---
 pkg/tcpip/transport/tcp/endpoint.go |  30 +++++---
 pkg/tcpip/transport/tcp/rcv.go      |   6 --
 pkg/tcpip/transport/tcp/tcp_test.go | 139 ++++++++++++++++++++++++++++++++++++
 3 files changed, 161 insertions(+), 14 deletions(-)

(limited to 'pkg/tcpip/transport/tcp')

diff --git a/pkg/tcpip/transport/tcp/endpoint.go b/pkg/tcpip/transport/tcp/endpoint.go
index fe629aa40..5d42f8045 100644
--- a/pkg/tcpip/transport/tcp/endpoint.go
+++ b/pkg/tcpip/transport/tcp/endpoint.go
@@ -955,10 +955,20 @@ func (e *endpoint) readLocked() (buffer.View, *tcpip.Error) {
 	}
 
 	e.rcvBufUsed -= len(v)
+
+	avail := e.receiveBufferAvailableLocked()
+
+	// If the window was small before, lower than MSS, send immediate
+	// ack. Without this, the sender might be stuck  waiting for the
+	// window to grow, while we think the window is non-zero so we
+	// don't need to send acks. To avoid silly window syndrome, send
+	// ack only when the window grows above one MSS.
+	crossedMSS := avail-len(v) < int(e.amss) && avail >= int(e.amss)
+
 	// If the window was zero before this read and if the read freed up
 	// enough buffer space for the scaled window to be non-zero then notify
 	// the protocol goroutine to send a window update.
-	if e.zeroWindow && !e.zeroReceiveWindow(e.rcv.rcvWndScale) {
+	if (e.zeroWindow && !e.zeroReceiveWindow(e.rcv.rcvWndScale)) || crossedMSS {
 		e.zeroWindow = false
 		e.notifyProtocolGoroutine(notifyNonZeroReceiveWindow)
 	}
@@ -1138,11 +1148,8 @@ func (e *endpoint) Peek(vec [][]byte) (int64, tcpip.ControlMessages, *tcpip.Erro
 //
 // It must be called with rcvListMu held.
 func (e *endpoint) zeroReceiveWindow(scale uint8) bool {
-	if e.rcvBufUsed >= e.rcvBufSize {
-		return true
-	}
-
-	return ((e.rcvBufSize - e.rcvBufUsed) >> scale) == 0
+	avail := e.receiveBufferAvailableLocked()
+	return (avail >> scale) == 0
 }
 
 // SetSockOptInt sets a socket option.
@@ -1181,9 +1188,16 @@ func (e *endpoint) SetSockOptInt(opt tcpip.SockOpt, v int) *tcpip.Error {
 			size = math.MaxInt32 / 2
 		}
 
+		availBefore := e.receiveBufferAvailableLocked()
 		e.rcvBufSize = size
+		availAfter := e.receiveBufferAvailableLocked()
+
 		e.rcvAutoParams.disabled = true
-		if e.zeroWindow && !e.zeroReceiveWindow(scale) {
+
+		// Immediatelly send ACK in two cases: when the buffer
+		// grows so that it leaves zero-window state, when the
+		// buffer grows from small < MSS to >= MSS.
+		if (e.zeroWindow && !e.zeroReceiveWindow(scale)) || (availBefore < int(e.amss) && availAfter >= int(e.amss)) {
 			e.zeroWindow = false
 			mask |= notifyNonZeroReceiveWindow
 		}
@@ -2229,7 +2243,7 @@ func (e *endpoint) readyToRead(s *segment) {
 		// we set the zero window before we deliver the segment to ensure
 		// that a subsequent read of the segment will correctly trigger
 		// a non-zero notification.
-		if avail := e.receiveBufferAvailableLocked(); avail>>e.rcv.rcvWndScale == 0 {
+		if e.zeroReceiveWindow(e.rcv.rcvWndScale) {
 			e.stats.ReceiveErrors.ZeroRcvWindowState.Increment()
 			e.zeroWindow = true
 		}
diff --git a/pkg/tcpip/transport/tcp/rcv.go b/pkg/tcpip/transport/tcp/rcv.go
index 0a5534959..05c8488f8 100644
--- a/pkg/tcpip/transport/tcp/rcv.go
+++ b/pkg/tcpip/transport/tcp/rcv.go
@@ -98,12 +98,6 @@ func (r *receiver) getSendParams() (rcvNxt seqnum.Value, rcvWnd seqnum.Size) {
 // in such cases we may need to send an ack to indicate to our peer that it can
 // resume sending data.
 func (r *receiver) nonZeroWindow() {
-	if (r.rcvAcc-r.rcvNxt)>>r.rcvWndScale != 0 {
-		// We never got around to announcing a zero window size, so we
-		// don't need to immediately announce a nonzero one.
-		return
-	}
-
 	// Immediately send an ack.
 	r.ep.snd.sendAck()
 }
diff --git a/pkg/tcpip/transport/tcp/tcp_test.go b/pkg/tcpip/transport/tcp/tcp_test.go
index e8fe4dab5..a05365c6a 100644
--- a/pkg/tcpip/transport/tcp/tcp_test.go
+++ b/pkg/tcpip/transport/tcp/tcp_test.go
@@ -6561,3 +6561,142 @@ func TestKeepaliveWithUserTimeout(t *testing.T) {
 		t.Errorf("got c.Stack().Stats().TCP.EstablishedTimedout = %v, want = %v", got, want)
 	}
 }
+
+func TestIncreaseWindowOnReceive(t *testing.T) {
+	// This test ensures that the endpoint sends an ack,
+	// after recv() when the window grows to more than 1 MSS.
+	c := context.New(t, defaultMTU)
+	defer c.Cleanup()
+
+	const rcvBuf = 65535 * 10
+	c.CreateConnected(789, 30000, rcvBuf)
+
+	// Write chunks of ~30000 bytes. It's important that two
+	// payloads make it equal or longer than MSS.
+	remain := rcvBuf
+	sent := 0
+	data := make([]byte, defaultMTU/2)
+	lastWnd := uint16(0)
+
+	for remain > len(data) {
+		c.SendPacket(data, &context.Headers{
+			SrcPort: context.TestPort,
+			DstPort: c.Port,
+			Flags:   header.TCPFlagAck,
+			SeqNum:  seqnum.Value(790 + sent),
+			AckNum:  c.IRS.Add(1),
+			RcvWnd:  30000,
+		})
+		sent += len(data)
+		remain -= len(data)
+
+		lastWnd = uint16(remain)
+		if remain > 0xffff {
+			lastWnd = 0xffff
+		}
+		checker.IPv4(t, c.GetPacket(),
+			checker.PayloadLen(header.TCPMinimumSize),
+			checker.TCP(
+				checker.DstPort(context.TestPort),
+				checker.SeqNum(uint32(c.IRS)+1),
+				checker.AckNum(uint32(790+sent)),
+				checker.Window(lastWnd),
+				checker.TCPFlags(header.TCPFlagAck),
+			),
+		)
+	}
+
+	if lastWnd == 0xffff || lastWnd == 0 {
+		t.Fatalf("expected small, non-zero window: %d", lastWnd)
+	}
+
+	// We now have < 1 MSS in the buffer space.  Read the data! An
+	// ack should be sent in response to that. The window was not
+	// zero, but it grew to larger than MSS.
+	_, _, err := c.EP.Read(nil)
+	if err != nil {
+		t.Fatalf("Read failed: %v", err)
+	}
+
+	_, _, err = c.EP.Read(nil)
+	if err != nil {
+		t.Fatalf("Read failed: %v", err)
+	}
+
+	// After reading two packets, we surely crossed MSS. See the ack:
+	checker.IPv4(t, c.GetPacket(),
+		checker.PayloadLen(header.TCPMinimumSize),
+		checker.TCP(
+			checker.DstPort(context.TestPort),
+			checker.SeqNum(uint32(c.IRS)+1),
+			checker.AckNum(uint32(790+sent)),
+			checker.Window(uint16(0xffff)),
+			checker.TCPFlags(header.TCPFlagAck),
+		),
+	)
+}
+
+func TestIncreaseWindowOnBufferResize(t *testing.T) {
+	// This test ensures that the endpoint sends an ack,
+	// after available recv buffer grows to more than 1 MSS.
+	c := context.New(t, defaultMTU)
+	defer c.Cleanup()
+
+	const rcvBuf = 65535 * 10
+	c.CreateConnected(789, 30000, rcvBuf)
+
+	// Write chunks of ~30000 bytes. It's important that two
+	// payloads make it equal or longer than MSS.
+	remain := rcvBuf
+	sent := 0
+	data := make([]byte, defaultMTU/2)
+	lastWnd := uint16(0)
+
+	for remain > len(data) {
+		c.SendPacket(data, &context.Headers{
+			SrcPort: context.TestPort,
+			DstPort: c.Port,
+			Flags:   header.TCPFlagAck,
+			SeqNum:  seqnum.Value(790 + sent),
+			AckNum:  c.IRS.Add(1),
+			RcvWnd:  30000,
+		})
+		sent += len(data)
+		remain -= len(data)
+
+		lastWnd = uint16(remain)
+		if remain > 0xffff {
+			lastWnd = 0xffff
+		}
+		checker.IPv4(t, c.GetPacket(),
+			checker.PayloadLen(header.TCPMinimumSize),
+			checker.TCP(
+				checker.DstPort(context.TestPort),
+				checker.SeqNum(uint32(c.IRS)+1),
+				checker.AckNum(uint32(790+sent)),
+				checker.Window(lastWnd),
+				checker.TCPFlags(header.TCPFlagAck),
+			),
+		)
+	}
+
+	if lastWnd == 0xffff || lastWnd == 0 {
+		t.Fatalf("expected small, non-zero window: %d", lastWnd)
+	}
+
+	// Increasing the buffer from should generate an ACK,
+	// since window grew from small value to larger equal MSS
+	c.EP.SetSockOptInt(tcpip.ReceiveBufferSizeOption, rcvBuf*2)
+
+	// After reading two packets, we surely crossed MSS. See the ack:
+	checker.IPv4(t, c.GetPacket(),
+		checker.PayloadLen(header.TCPMinimumSize),
+		checker.TCP(
+			checker.DstPort(context.TestPort),
+			checker.SeqNum(uint32(c.IRS)+1),
+			checker.AckNum(uint32(790+sent)),
+			checker.Window(uint16(0xffff)),
+			checker.TCPFlags(header.TCPFlagAck),
+		),
+	)
+}
-- 
cgit v1.2.3


From c276e4740f225068dc394a500dfdddd64af1d18a Mon Sep 17 00:00:00 2001
From: Marek Majkowski <marek@cloudflare.com>
Date: Wed, 8 Jan 2020 12:56:39 +0000
Subject: Fix #1522 - implement silly window sydrome protection on rx side

Before, each of small read()'s that raises window either from zero
or above threshold of aMSS, would generate an ACK. In a classic
silly-window-syndrome scenario, we can imagine a pessimistic case
when small read()'s generate a stream of ACKs.

This PR fixes that, essentially treating window size < aMSS as zero.
We send ACK exactly in a moment when window increases to >= aMSS
or half of receive buffer size (whichever smaller).
---
 pkg/tcpip/transport/tcp/endpoint.go | 73 +++++++++++++++++++++----------------
 pkg/tcpip/transport/tcp/tcp_test.go | 14 ++++---
 2 files changed, 51 insertions(+), 36 deletions(-)

(limited to 'pkg/tcpip/transport/tcp')

diff --git a/pkg/tcpip/transport/tcp/endpoint.go b/pkg/tcpip/transport/tcp/endpoint.go
index 5d42f8045..8ff125855 100644
--- a/pkg/tcpip/transport/tcp/endpoint.go
+++ b/pkg/tcpip/transport/tcp/endpoint.go
@@ -956,20 +956,11 @@ func (e *endpoint) readLocked() (buffer.View, *tcpip.Error) {
 
 	e.rcvBufUsed -= len(v)
 
-	avail := e.receiveBufferAvailableLocked()
-
-	// If the window was small before, lower than MSS, send immediate
-	// ack. Without this, the sender might be stuck  waiting for the
-	// window to grow, while we think the window is non-zero so we
-	// don't need to send acks. To avoid silly window syndrome, send
-	// ack only when the window grows above one MSS.
-	crossedMSS := avail-len(v) < int(e.amss) && avail >= int(e.amss)
-
-	// If the window was zero before this read and if the read freed up
-	// enough buffer space for the scaled window to be non-zero then notify
-	// the protocol goroutine to send a window update.
-	if (e.zeroWindow && !e.zeroReceiveWindow(e.rcv.rcvWndScale)) || crossedMSS {
-		e.zeroWindow = false
+	// If the window was small before this read and if the read
+	// freed up enough buffer space, to either fit an aMSS or half
+	// a receive buffer (whichever smaller), then notify the
+	// protocol goroutine to send a window update.
+	if e.windowCrossedACKThreshold(len(v)) == 1 {
 		e.notifyProtocolGoroutine(notifyNonZeroReceiveWindow)
 	}
 
@@ -1143,13 +1134,35 @@ func (e *endpoint) Peek(vec [][]byte) (int64, tcpip.ControlMessages, *tcpip.Erro
 	return num, tcpip.ControlMessages{}, nil
 }
 
-// zeroReceiveWindow checks if the receive window to be announced now would be
-// zero, based on the amount of available buffer and the receive window scaling.
+// windowCrossedACKThreshold checks if the receive window to be announced now would be
+// under aMSS or under half receive buffer, whichever smaller. This is useful as
+// a receive side silly window syndrome prevention mechanism. If window grows
+// to reasonable value, we should send ACK to the sender to inform the rx space is now
+// large. We also want ensure a series of small read()'s won't trigger a flood of
+// spurious tiny ACK's.
 //
-// It must be called with rcvListMu held.
-func (e *endpoint) zeroReceiveWindow(scale uint8) bool {
-	avail := e.receiveBufferAvailableLocked()
-	return (avail >> scale) == 0
+// For large receive buffers, the threshold is aMSS - once reader reads more than aMSS
+// we'll send ACK. For tiny receive buffers, the threshold is half of receive buffer size.
+// This is chosen arbitrairly.
+func (e *endpoint) windowCrossedACKThreshold(deltaBefore int) int {
+	newAvail := e.receiveBufferAvailableLocked()
+	oldAvail := newAvail - deltaBefore
+	if oldAvail < 0 {
+		oldAvail = 0
+	}
+
+	threshold := int(e.amss)
+	if threshold > e.rcvBufSize/2 {
+		threshold = e.rcvBufSize / 2
+	}
+
+	switch {
+	case oldAvail < threshold && newAvail >= threshold:
+		return 1
+	case oldAvail >= threshold && newAvail < threshold:
+		return -1
+	}
+	return 0
 }
 
 // SetSockOptInt sets a socket option.
@@ -1194,11 +1207,11 @@ func (e *endpoint) SetSockOptInt(opt tcpip.SockOpt, v int) *tcpip.Error {
 
 		e.rcvAutoParams.disabled = true
 
-		// Immediatelly send ACK in two cases: when the buffer
-		// grows so that it leaves zero-window state, when the
-		// buffer grows from small < MSS to >= MSS.
-		if (e.zeroWindow && !e.zeroReceiveWindow(scale)) || (availBefore < int(e.amss) && availAfter >= int(e.amss)) {
-			e.zeroWindow = false
+		// Immediatelly send an ACK to uncork the sender silly
+		// window syndrome prevetion, when our available space
+		// grows above aMSS or half receive buffer, whichever
+		// smaller.
+		if e.windowCrossedACKThreshold(availAfter-availBefore) == 1 {
 			mask |= notifyNonZeroReceiveWindow
 		}
 		e.rcvListMu.Unlock()
@@ -2239,13 +2252,11 @@ func (e *endpoint) readyToRead(s *segment) {
 	if s != nil {
 		s.incRef()
 		e.rcvBufUsed += s.data.Size()
-		// Check if the receive window is now closed. If so make sure
-		// we set the zero window before we deliver the segment to ensure
-		// that a subsequent read of the segment will correctly trigger
-		// a non-zero notification.
-		if e.zeroReceiveWindow(e.rcv.rcvWndScale) {
+		// Increase counter if the receive window falls down
+		// below MSS or half receive buffer size, whichever
+		// smaller.
+		if e.windowCrossedACKThreshold(-s.data.Size()) == -1 {
 			e.stats.ReceiveErrors.ZeroRcvWindowState.Increment()
-			e.zeroWindow = true
 		}
 		e.rcvList.PushBack(s)
 	} else {
diff --git a/pkg/tcpip/transport/tcp/tcp_test.go b/pkg/tcpip/transport/tcp/tcp_test.go
index a05365c6a..4c2e458e3 100644
--- a/pkg/tcpip/transport/tcp/tcp_test.go
+++ b/pkg/tcpip/transport/tcp/tcp_test.go
@@ -2091,10 +2091,14 @@ func TestZeroScaledWindowReceive(t *testing.T) {
 		)
 	}
 
-	// Read some data. An ack should be sent in response to that.
-	v, _, err := c.EP.Read(nil)
-	if err != nil {
-		t.Fatalf("Read failed: %v", err)
+	// Read at least 1MSS of data. An ack should be sent in response to that.
+	sz := 0
+	for sz < defaultMTU {
+		v, _, err := c.EP.Read(nil)
+		if err != nil {
+			t.Fatalf("Read failed: %v", err)
+		}
+		sz += len(v)
 	}
 
 	checker.IPv4(t, c.GetPacket(),
@@ -2103,7 +2107,7 @@ func TestZeroScaledWindowReceive(t *testing.T) {
 			checker.DstPort(context.TestPort),
 			checker.SeqNum(uint32(c.IRS)+1),
 			checker.AckNum(uint32(790+sent)),
-			checker.Window(uint16(len(v)>>ws)),
+			checker.Window(uint16(sz>>ws)),
 			checker.TCPFlags(header.TCPFlagAck),
 		),
 	)
-- 
cgit v1.2.3


From a271bccfc61390be64ca0175b8fc7d20e66d05b6 Mon Sep 17 00:00:00 2001
From: Tamir Duberstein <tamird@google.com>
Date: Wed, 8 Jan 2020 14:16:38 -0800
Subject: Rename tcpip.SockOpt{,Int}

PiperOrigin-RevId: 288772878
---
 pkg/sentry/socket/netstack/netstack.go   |  4 ++--
 pkg/sentry/socket/unix/transport/unix.go |  8 ++++----
 pkg/tcpip/stack/transport_test.go        |  4 ++--
 pkg/tcpip/tcpip.go                       | 10 +++++-----
 pkg/tcpip/transport/icmp/endpoint.go     |  4 ++--
 pkg/tcpip/transport/packet/endpoint.go   |  4 ++--
 pkg/tcpip/transport/raw/endpoint.go      |  4 ++--
 pkg/tcpip/transport/tcp/endpoint.go      |  4 ++--
 pkg/tcpip/transport/udp/endpoint.go      |  4 ++--
 9 files changed, 23 insertions(+), 23 deletions(-)

(limited to 'pkg/tcpip/transport/tcp')

diff --git a/pkg/sentry/socket/netstack/netstack.go b/pkg/sentry/socket/netstack/netstack.go
index 140851c17..5f91a0d1a 100644
--- a/pkg/sentry/socket/netstack/netstack.go
+++ b/pkg/sentry/socket/netstack/netstack.go
@@ -224,7 +224,7 @@ type commonEndpoint interface {
 
 	// SetSockOptInt implements tcpip.Endpoint.SetSockOptInt and
 	// transport.Endpoint.SetSockOptInt.
-	SetSockOptInt(opt tcpip.SockOpt, v int) *tcpip.Error
+	SetSockOptInt(opt tcpip.SockOptInt, v int) *tcpip.Error
 
 	// GetSockOpt implements tcpip.Endpoint.GetSockOpt and
 	// transport.Endpoint.GetSockOpt.
@@ -232,7 +232,7 @@ type commonEndpoint interface {
 
 	// GetSockOptInt implements tcpip.Endpoint.GetSockOptInt and
 	// transport.Endpoint.GetSockOpt.
-	GetSockOptInt(opt tcpip.SockOpt) (int, *tcpip.Error)
+	GetSockOptInt(opt tcpip.SockOptInt) (int, *tcpip.Error)
 }
 
 // SocketOperations encapsulates all the state needed to represent a network stack
diff --git a/pkg/sentry/socket/unix/transport/unix.go b/pkg/sentry/socket/unix/transport/unix.go
index 529a7a7a9..fcba49435 100644
--- a/pkg/sentry/socket/unix/transport/unix.go
+++ b/pkg/sentry/socket/unix/transport/unix.go
@@ -177,7 +177,7 @@ type Endpoint interface {
 
 	// SetSockOptInt sets a socket option for simple cases when a value has
 	// the int type.
-	SetSockOptInt(opt tcpip.SockOpt, v int) *tcpip.Error
+	SetSockOptInt(opt tcpip.SockOptInt, v int) *tcpip.Error
 
 	// GetSockOpt gets a socket option. opt should be a pointer to one of the
 	// tcpip.*Option types.
@@ -185,7 +185,7 @@ type Endpoint interface {
 
 	// GetSockOptInt gets a socket option for simple cases when a return
 	// value has the int type.
-	GetSockOptInt(opt tcpip.SockOpt) (int, *tcpip.Error)
+	GetSockOptInt(opt tcpip.SockOptInt) (int, *tcpip.Error)
 
 	// State returns the current state of the socket, as represented by Linux in
 	// procfs.
@@ -851,11 +851,11 @@ func (e *baseEndpoint) SetSockOpt(opt interface{}) *tcpip.Error {
 	return nil
 }
 
-func (e *baseEndpoint) SetSockOptInt(opt tcpip.SockOpt, v int) *tcpip.Error {
+func (e *baseEndpoint) SetSockOptInt(opt tcpip.SockOptInt, v int) *tcpip.Error {
 	return nil
 }
 
-func (e *baseEndpoint) GetSockOptInt(opt tcpip.SockOpt) (int, *tcpip.Error) {
+func (e *baseEndpoint) GetSockOptInt(opt tcpip.SockOptInt) (int, *tcpip.Error) {
 	switch opt {
 	case tcpip.ReceiveQueueSizeOption:
 		v := 0
diff --git a/pkg/tcpip/stack/transport_test.go b/pkg/tcpip/stack/transport_test.go
index 748ce4ea5..095346f0b 100644
--- a/pkg/tcpip/stack/transport_test.go
+++ b/pkg/tcpip/stack/transport_test.go
@@ -103,12 +103,12 @@ func (*fakeTransportEndpoint) SetSockOpt(interface{}) *tcpip.Error {
 }
 
 // SetSockOptInt sets a socket option. Currently not supported.
-func (*fakeTransportEndpoint) SetSockOptInt(tcpip.SockOpt, int) *tcpip.Error {
+func (*fakeTransportEndpoint) SetSockOptInt(tcpip.SockOptInt, int) *tcpip.Error {
 	return tcpip.ErrInvalidEndpointState
 }
 
 // GetSockOptInt implements tcpip.Endpoint.GetSockOptInt.
-func (*fakeTransportEndpoint) GetSockOptInt(opt tcpip.SockOpt) (int, *tcpip.Error) {
+func (*fakeTransportEndpoint) GetSockOptInt(opt tcpip.SockOptInt) (int, *tcpip.Error) {
 	return -1, tcpip.ErrUnknownProtocolOption
 }
 
diff --git a/pkg/tcpip/tcpip.go b/pkg/tcpip/tcpip.go
index f62fd729f..b172d71b0 100644
--- a/pkg/tcpip/tcpip.go
+++ b/pkg/tcpip/tcpip.go
@@ -425,7 +425,7 @@ type Endpoint interface {
 
 	// SetSockOptInt sets a socket option, for simple cases where a value
 	// has the int type.
-	SetSockOptInt(opt SockOpt, v int) *Error
+	SetSockOptInt(opt SockOptInt, v int) *Error
 
 	// GetSockOpt gets a socket option. opt should be a pointer to one of the
 	// *Option types.
@@ -433,7 +433,7 @@ type Endpoint interface {
 
 	// GetSockOptInt gets a socket option for simple cases where a return
 	// value has the int type.
-	GetSockOptInt(SockOpt) (int, *Error)
+	GetSockOptInt(SockOptInt) (int, *Error)
 
 	// State returns a socket's lifecycle state. The returned value is
 	// protocol-specific and is primarily used for diagnostics.
@@ -488,13 +488,13 @@ type WriteOptions struct {
 	Atomic bool
 }
 
-// SockOpt represents socket options which values have the int type.
-type SockOpt int
+// SockOptInt represents socket options which values have the int type.
+type SockOptInt int
 
 const (
 	// ReceiveQueueSizeOption is used in GetSockOptInt to specify that the
 	// number of unread bytes in the input buffer should be returned.
-	ReceiveQueueSizeOption SockOpt = iota
+	ReceiveQueueSizeOption SockOptInt = iota
 
 	// SendBufferSizeOption is used by SetSockOptInt/GetSockOptInt to
 	// specify the send buffer size option.
diff --git a/pkg/tcpip/transport/icmp/endpoint.go b/pkg/tcpip/transport/icmp/endpoint.go
index 9c40931b5..5816ce49a 100644
--- a/pkg/tcpip/transport/icmp/endpoint.go
+++ b/pkg/tcpip/transport/icmp/endpoint.go
@@ -351,12 +351,12 @@ func (e *endpoint) SetSockOpt(opt interface{}) *tcpip.Error {
 }
 
 // SetSockOptInt sets a socket option. Currently not supported.
-func (e *endpoint) SetSockOptInt(opt tcpip.SockOpt, v int) *tcpip.Error {
+func (e *endpoint) SetSockOptInt(opt tcpip.SockOptInt, v int) *tcpip.Error {
 	return nil
 }
 
 // GetSockOptInt implements tcpip.Endpoint.GetSockOptInt.
-func (e *endpoint) GetSockOptInt(opt tcpip.SockOpt) (int, *tcpip.Error) {
+func (e *endpoint) GetSockOptInt(opt tcpip.SockOptInt) (int, *tcpip.Error) {
 	switch opt {
 	case tcpip.ReceiveQueueSizeOption:
 		v := 0
diff --git a/pkg/tcpip/transport/packet/endpoint.go b/pkg/tcpip/transport/packet/endpoint.go
index 0010b5e5f..6360ce880 100644
--- a/pkg/tcpip/transport/packet/endpoint.go
+++ b/pkg/tcpip/transport/packet/endpoint.go
@@ -251,12 +251,12 @@ func (ep *endpoint) SetSockOpt(opt interface{}) *tcpip.Error {
 }
 
 // SetSockOptInt implements tcpip.Endpoint.SetSockOptInt.
-func (ep *endpoint) SetSockOptInt(opt tcpip.SockOpt, v int) *tcpip.Error {
+func (ep *endpoint) SetSockOptInt(opt tcpip.SockOptInt, v int) *tcpip.Error {
 	return tcpip.ErrUnknownProtocolOption
 }
 
 // GetSockOptInt implements tcpip.Endpoint.GetSockOptInt.
-func (ep *endpoint) GetSockOptInt(opt tcpip.SockOpt) (int, *tcpip.Error) {
+func (ep *endpoint) GetSockOptInt(opt tcpip.SockOptInt) (int, *tcpip.Error) {
 	return 0, tcpip.ErrNotSupported
 }
 
diff --git a/pkg/tcpip/transport/raw/endpoint.go b/pkg/tcpip/transport/raw/endpoint.go
index 5aafe2615..0fd9c456a 100644
--- a/pkg/tcpip/transport/raw/endpoint.go
+++ b/pkg/tcpip/transport/raw/endpoint.go
@@ -510,12 +510,12 @@ func (e *endpoint) SetSockOpt(opt interface{}) *tcpip.Error {
 }
 
 // SetSockOptInt implements tcpip.Endpoint.SetSockOptInt.
-func (ep *endpoint) SetSockOptInt(opt tcpip.SockOpt, v int) *tcpip.Error {
+func (e *endpoint) SetSockOptInt(opt tcpip.SockOptInt, v int) *tcpip.Error {
 	return tcpip.ErrUnknownProtocolOption
 }
 
 // GetSockOptInt implements tcpip.Endpoint.GetSockOptInt.
-func (e *endpoint) GetSockOptInt(opt tcpip.SockOpt) (int, *tcpip.Error) {
+func (e *endpoint) GetSockOptInt(opt tcpip.SockOptInt) (int, *tcpip.Error) {
 	switch opt {
 	case tcpip.ReceiveQueueSizeOption:
 		v := 0
diff --git a/pkg/tcpip/transport/tcp/endpoint.go b/pkg/tcpip/transport/tcp/endpoint.go
index fe629aa40..f79154b95 100644
--- a/pkg/tcpip/transport/tcp/endpoint.go
+++ b/pkg/tcpip/transport/tcp/endpoint.go
@@ -1146,7 +1146,7 @@ func (e *endpoint) zeroReceiveWindow(scale uint8) bool {
 }
 
 // SetSockOptInt sets a socket option.
-func (e *endpoint) SetSockOptInt(opt tcpip.SockOpt, v int) *tcpip.Error {
+func (e *endpoint) SetSockOptInt(opt tcpip.SockOptInt, v int) *tcpip.Error {
 	switch opt {
 	case tcpip.ReceiveBufferSizeOption:
 		// Make sure the receive buffer size is within the min and max
@@ -1447,7 +1447,7 @@ func (e *endpoint) readyReceiveSize() (int, *tcpip.Error) {
 }
 
 // GetSockOptInt implements tcpip.Endpoint.GetSockOptInt.
-func (e *endpoint) GetSockOptInt(opt tcpip.SockOpt) (int, *tcpip.Error) {
+func (e *endpoint) GetSockOptInt(opt tcpip.SockOptInt) (int, *tcpip.Error) {
 	switch opt {
 	case tcpip.ReceiveQueueSizeOption:
 		return e.readyReceiveSize()
diff --git a/pkg/tcpip/transport/udp/endpoint.go b/pkg/tcpip/transport/udp/endpoint.go
index 1ac4705af..dae373ea7 100644
--- a/pkg/tcpip/transport/udp/endpoint.go
+++ b/pkg/tcpip/transport/udp/endpoint.go
@@ -457,7 +457,7 @@ func (e *endpoint) Peek([][]byte) (int64, tcpip.ControlMessages, *tcpip.Error) {
 }
 
 // SetSockOptInt implements tcpip.Endpoint.SetSockOptInt.
-func (e *endpoint) SetSockOptInt(opt tcpip.SockOpt, v int) *tcpip.Error {
+func (e *endpoint) SetSockOptInt(opt tcpip.SockOptInt, v int) *tcpip.Error {
 	return nil
 }
 
@@ -661,7 +661,7 @@ func (e *endpoint) SetSockOpt(opt interface{}) *tcpip.Error {
 }
 
 // GetSockOptInt implements tcpip.Endpoint.GetSockOptInt.
-func (e *endpoint) GetSockOptInt(opt tcpip.SockOpt) (int, *tcpip.Error) {
+func (e *endpoint) GetSockOptInt(opt tcpip.SockOptInt) (int, *tcpip.Error) {
 	switch opt {
 	case tcpip.ReceiveQueueSizeOption:
 		v := 0
-- 
cgit v1.2.3


From e21c5840569155d39e8e11ac18cee99bc6d67469 Mon Sep 17 00:00:00 2001
From: Bert Muthalaly <stijlist@google.com>
Date: Wed, 8 Jan 2020 14:49:12 -0800
Subject: Combine various Create*NIC methods into CreateNICWithOptions.

PiperOrigin-RevId: 288779416
---
 pkg/tcpip/stack/ndp_test.go                        |  6 +--
 pkg/tcpip/stack/stack.go                           | 46 ++++++++++------------
 pkg/tcpip/stack/stack_test.go                      | 10 +++--
 pkg/tcpip/stack/transport_demuxer_test.go          |  5 ++-
 pkg/tcpip/transport/tcp/tcp_test.go                |  5 ++-
 pkg/tcpip/transport/tcp/testing/context/context.go | 10 +++--
 pkg/tcpip/transport/udp/udp_test.go                |  5 ++-
 runsc/boot/network.go                              |  5 ++-
 8 files changed, 47 insertions(+), 45 deletions(-)

(limited to 'pkg/tcpip/transport/tcp')

diff --git a/pkg/tcpip/stack/ndp_test.go b/pkg/tcpip/stack/ndp_test.go
index 8d89859ba..070d80c8d 100644
--- a/pkg/tcpip/stack/ndp_test.go
+++ b/pkg/tcpip/stack/ndp_test.go
@@ -2500,9 +2500,9 @@ func TestAutoGenAddrWithOpaqueIID(t *testing.T) {
 			SecretKey: secretKey,
 		},
 	})
-
-	if err := s.CreateNamedNIC(nicID, nicName, e); err != nil {
-		t.Fatalf("CreateNamedNIC(%d, %q, _) = %s", nicID, nicName, err)
+	opts := stack.NICOptions{Name: nicName}
+	if err := s.CreateNICWithOptions(nicID, e, opts); err != nil {
+		t.Fatalf("CreateNICWithOptions(%d, _, %+v, _) = %s", nicID, opts, err)
 	}
 
 	expectAutoGenAddrEvent := func(addr tcpip.AddressWithPrefix, eventType ndpAutoGenAddrEventType) {
diff --git a/pkg/tcpip/stack/stack.go b/pkg/tcpip/stack/stack.go
index 807f910f6..fb7ac409e 100644
--- a/pkg/tcpip/stack/stack.go
+++ b/pkg/tcpip/stack/stack.go
@@ -796,9 +796,21 @@ func (s *Stack) NewPacketEndpoint(cooked bool, netProto tcpip.NetworkProtocolNum
 	return s.rawFactory.NewPacketEndpoint(s, cooked, netProto, waiterQueue)
 }
 
-// createNIC creates a NIC with the provided id and link-layer endpoint, and
-// optionally enable it.
-func (s *Stack) createNIC(id tcpip.NICID, name string, ep LinkEndpoint, enabled bool) *tcpip.Error {
+// NICOptions specifies the configuration of a NIC as it is being created.
+// The zero value creates an enabled, unnamed NIC.
+type NICOptions struct {
+	// Name specifies the name of the NIC.
+	Name string
+
+	// Disabled specifies whether to avoid calling Attach on the passed
+	// LinkEndpoint.
+	Disabled bool
+}
+
+// CreateNICWithOptions creates a NIC with the provided id, LinkEndpoint, and
+// NICOptions. See the documentation on type NICOptions for details on how
+// NICs can be configured.
+func (s *Stack) CreateNICWithOptions(id tcpip.NICID, ep LinkEndpoint, opts NICOptions) *tcpip.Error {
 	s.mu.Lock()
 	defer s.mu.Unlock()
 
@@ -807,38 +819,20 @@ func (s *Stack) createNIC(id tcpip.NICID, name string, ep LinkEndpoint, enabled
 		return tcpip.ErrDuplicateNICID
 	}
 
-	n := newNIC(s, id, name, ep)
+	n := newNIC(s, id, opts.Name, ep)
 
 	s.nics[id] = n
-	if enabled {
+	if !opts.Disabled {
 		return n.enable()
 	}
 
 	return nil
 }
 
-// CreateNIC creates a NIC with the provided id and link-layer endpoint.
+// CreateNIC creates a NIC with the provided id and LinkEndpoint and calls
+// `LinkEndpoint.Attach` to start delivering packets to it.
 func (s *Stack) CreateNIC(id tcpip.NICID, ep LinkEndpoint) *tcpip.Error {
-	return s.createNIC(id, "", ep, true)
-}
-
-// CreateNamedNIC creates a NIC with the provided id and link-layer endpoint,
-// and a human-readable name.
-func (s *Stack) CreateNamedNIC(id tcpip.NICID, name string, ep LinkEndpoint) *tcpip.Error {
-	return s.createNIC(id, name, ep, true)
-}
-
-// CreateDisabledNIC creates a NIC with the provided id and link-layer endpoint,
-// but leave it disable. Stack.EnableNIC must be called before the link-layer
-// endpoint starts delivering packets to it.
-func (s *Stack) CreateDisabledNIC(id tcpip.NICID, ep LinkEndpoint) *tcpip.Error {
-	return s.createNIC(id, "", ep, false)
-}
-
-// CreateDisabledNamedNIC is a combination of CreateNamedNIC and
-// CreateDisabledNIC.
-func (s *Stack) CreateDisabledNamedNIC(id tcpip.NICID, name string, ep LinkEndpoint) *tcpip.Error {
-	return s.createNIC(id, name, ep, false)
+	return s.CreateNICWithOptions(id, ep, NICOptions{})
 }
 
 // EnableNIC enables the given NIC so that the link-layer endpoint can start
diff --git a/pkg/tcpip/stack/stack_test.go b/pkg/tcpip/stack/stack_test.go
index 33f20579f..9ac50bb23 100644
--- a/pkg/tcpip/stack/stack_test.go
+++ b/pkg/tcpip/stack/stack_test.go
@@ -2097,8 +2097,9 @@ func TestNICAutoGenAddrWithOpaque(t *testing.T) {
 
 			e := channel.New(10, 1280, test.linkAddr)
 			s := stack.New(opts)
-			if err := s.CreateNamedNIC(nicID, test.nicName, e); err != nil {
-				t.Fatalf("CreateNamedNIC(%d, %q, _) = %s", nicID, test.nicName, err)
+			nicOpts := stack.NICOptions{Name: test.nicName}
+			if err := s.CreateNICWithOptions(nicID, e, nicOpts); err != nil {
+				t.Fatalf("CreateNICWithOptions(%d, _, %+v) = %s", nicID, opts, err)
 			}
 
 			addr, err := s.GetMainNICAddress(nicID, header.IPv6ProtocolNumber)
@@ -2156,8 +2157,9 @@ func TestNoLinkLocalAutoGenForLoopbackNIC(t *testing.T) {
 
 			e := loopback.New()
 			s := stack.New(opts)
-			if err := s.CreateNamedNIC(nicID, nicName, e); err != nil {
-				t.Fatalf("CreateNamedNIC(%d, %q, _) = %s", nicID, nicName, err)
+			nicOpts := stack.NICOptions{Name: nicName}
+			if err := s.CreateNICWithOptions(nicID, e, nicOpts); err != nil {
+				t.Fatalf("CreateNICWithOptions(%d, _, %+v) = %s", nicID, nicOpts, err)
 			}
 
 			addr, err := s.GetMainNICAddress(nicID, header.IPv6ProtocolNumber)
diff --git a/pkg/tcpip/stack/transport_demuxer_test.go b/pkg/tcpip/stack/transport_demuxer_test.go
index 3b28b06d0..33dbc0536 100644
--- a/pkg/tcpip/stack/transport_demuxer_test.go
+++ b/pkg/tcpip/stack/transport_demuxer_test.go
@@ -80,8 +80,9 @@ func newDualTestContextMultiNic(t *testing.T, mtu uint32, linkEpNames []string)
 	for i, linkEpName := range linkEpNames {
 		channelEP := channel.New(256, mtu, "")
 		nicID := tcpip.NICID(i + 1)
-		if err := s.CreateNamedNIC(nicID, linkEpName, channelEP); err != nil {
-			t.Fatalf("CreateNIC failed: %v", err)
+		opts := stack.NICOptions{Name: linkEpName}
+		if err := s.CreateNICWithOptions(nicID, channelEP, opts); err != nil {
+			t.Fatalf("CreateNICWithOptions(_, _, %+v) failed: %v", opts, err)
 		}
 		linkEPs[linkEpName] = channelEP
 
diff --git a/pkg/tcpip/transport/tcp/tcp_test.go b/pkg/tcpip/transport/tcp/tcp_test.go
index e8fe4dab5..9d7b0910d 100644
--- a/pkg/tcpip/transport/tcp/tcp_test.go
+++ b/pkg/tcpip/transport/tcp/tcp_test.go
@@ -3794,8 +3794,9 @@ func TestBindToDeviceOption(t *testing.T) {
 	}
 	defer ep.Close()
 
-	if err := s.CreateNamedNIC(321, "my_device", loopback.New()); err != nil {
-		t.Errorf("CreateNamedNIC failed: %v", err)
+	opts := stack.NICOptions{Name: "my_device"}
+	if err := s.CreateNICWithOptions(321, loopback.New(), opts); err != nil {
+		t.Errorf("CreateNICWithOptions(_, _, %+v) failed: %v", opts, err)
 	}
 
 	// Make an nameless NIC.
diff --git a/pkg/tcpip/transport/tcp/testing/context/context.go b/pkg/tcpip/transport/tcp/testing/context/context.go
index b0a376eba..50c81aa65 100644
--- a/pkg/tcpip/transport/tcp/testing/context/context.go
+++ b/pkg/tcpip/transport/tcp/testing/context/context.go
@@ -158,15 +158,17 @@ func New(t *testing.T, mtu uint32) *Context {
 	if testing.Verbose() {
 		wep = sniffer.New(ep)
 	}
-	if err := s.CreateNamedNIC(1, "nic1", wep); err != nil {
-		t.Fatalf("CreateNIC failed: %v", err)
+	opts := stack.NICOptions{Name: "nic1"}
+	if err := s.CreateNICWithOptions(1, wep, opts); err != nil {
+		t.Fatalf("CreateNICWithOptions(_, _, %+v) failed: %v", opts, err)
 	}
 	wep2 := stack.LinkEndpoint(channel.New(1000, mtu, ""))
 	if testing.Verbose() {
 		wep2 = sniffer.New(channel.New(1000, mtu, ""))
 	}
-	if err := s.CreateNamedNIC(2, "nic2", wep2); err != nil {
-		t.Fatalf("CreateNIC failed: %v", err)
+	opts2 := stack.NICOptions{Name: "nic2"}
+	if err := s.CreateNICWithOptions(2, wep2, opts2); err != nil {
+		t.Fatalf("CreateNICWithOptions(_, _, %+v) failed: %v", opts2, err)
 	}
 
 	if err := s.AddAddress(1, ipv4.ProtocolNumber, StackAddr); err != nil {
diff --git a/pkg/tcpip/transport/udp/udp_test.go b/pkg/tcpip/transport/udp/udp_test.go
index 7051a7a9c..65382b7f1 100644
--- a/pkg/tcpip/transport/udp/udp_test.go
+++ b/pkg/tcpip/transport/udp/udp_test.go
@@ -508,8 +508,9 @@ func TestBindToDeviceOption(t *testing.T) {
 	}
 	defer ep.Close()
 
-	if err := s.CreateNamedNIC(321, "my_device", loopback.New()); err != nil {
-		t.Errorf("CreateNamedNIC failed: %v", err)
+	opts := stack.NICOptions{Name: "my_device"}
+	if err := s.CreateNICWithOptions(321, loopback.New(), opts); err != nil {
+		t.Errorf("CreateNICWithOptions(_, _, %+v) failed: %v", opts, err)
 	}
 
 	// Make an nameless NIC.
diff --git a/runsc/boot/network.go b/runsc/boot/network.go
index 0240fe323..6a8765ec8 100644
--- a/runsc/boot/network.go
+++ b/runsc/boot/network.go
@@ -219,8 +219,9 @@ func (n *Network) CreateLinksAndRoutes(args *CreateLinksAndRoutesArgs, _ *struct
 // createNICWithAddrs creates a NIC in the network stack and adds the given
 // addresses.
 func (n *Network) createNICWithAddrs(id tcpip.NICID, name string, ep stack.LinkEndpoint, addrs []net.IP) error {
-	if err := n.Stack.CreateNamedNIC(id, name, sniffer.New(ep)); err != nil {
-		return fmt.Errorf("CreateNamedNIC(%v, %v, %v) failed: %v", id, name, ep, err)
+	opts := stack.NICOptions{Name: name}
+	if err := n.Stack.CreateNICWithOptions(id, sniffer.New(ep), opts); err != nil {
+		return fmt.Errorf("CreateNICWithOptions(%d, _, %+v) failed: %v", id, opts, err)
 	}
 
 	// Always start with an arp address for the NIC.
-- 
cgit v1.2.3


From d530df2f95c3f75488ecc56b8fd205c3ee0966f8 Mon Sep 17 00:00:00 2001
From: Tamir Duberstein <tamird@google.com>
Date: Wed, 8 Jan 2020 15:39:22 -0800
Subject: Introduce tcpip.SockOptBool

...and port V6OnlyOption to it.

PiperOrigin-RevId: 288789451
---
 pkg/sentry/socket/netstack/netstack.go             | 21 ++++--
 pkg/sentry/socket/unix/transport/unix.go           | 16 +++++
 pkg/tcpip/stack/ndp_test.go                        | 15 ++---
 pkg/tcpip/stack/transport_demuxer_test.go          | 48 +++++++-------
 pkg/tcpip/stack/transport_test.go                  | 10 +++
 pkg/tcpip/tcpip.go                                 | 21 ++++--
 pkg/tcpip/transport/icmp/endpoint.go               | 10 +++
 pkg/tcpip/transport/packet/endpoint.go             | 22 +++++--
 pkg/tcpip/transport/raw/endpoint.go                | 40 +++++++-----
 pkg/tcpip/transport/tcp/dual_stack_test.go         |  8 +--
 pkg/tcpip/transport/tcp/endpoint.go                | 75 ++++++++++++----------
 pkg/tcpip/transport/tcp/tcp_test.go                |  8 +--
 pkg/tcpip/transport/tcp/testing/context/context.go |  6 +-
 pkg/tcpip/transport/udp/endpoint.go                | 60 +++++++++--------
 pkg/tcpip/transport/udp/udp_test.go                |  2 +-
 15 files changed, 224 insertions(+), 138 deletions(-)

(limited to 'pkg/tcpip/transport/tcp')

diff --git a/pkg/sentry/socket/netstack/netstack.go b/pkg/sentry/socket/netstack/netstack.go
index 5f91a0d1a..9e0d69046 100644
--- a/pkg/sentry/socket/netstack/netstack.go
+++ b/pkg/sentry/socket/netstack/netstack.go
@@ -222,6 +222,10 @@ type commonEndpoint interface {
 	// transport.Endpoint.SetSockOpt.
 	SetSockOpt(interface{}) *tcpip.Error
 
+	// SetSockOptBool implements tcpip.Endpoint.SetSockOptBool and
+	// transport.Endpoint.SetSockOptBool.
+	SetSockOptBool(opt tcpip.SockOptBool, v bool) *tcpip.Error
+
 	// SetSockOptInt implements tcpip.Endpoint.SetSockOptInt and
 	// transport.Endpoint.SetSockOptInt.
 	SetSockOptInt(opt tcpip.SockOptInt, v int) *tcpip.Error
@@ -230,6 +234,10 @@ type commonEndpoint interface {
 	// transport.Endpoint.GetSockOpt.
 	GetSockOpt(interface{}) *tcpip.Error
 
+	// GetSockOptBool implements tcpip.Endpoint.GetSockOptBool and
+	// transport.Endpoint.GetSockOpt.
+	GetSockOptBool(opt tcpip.SockOptBool) (bool, *tcpip.Error)
+
 	// GetSockOptInt implements tcpip.Endpoint.GetSockOptInt and
 	// transport.Endpoint.GetSockOpt.
 	GetSockOptInt(opt tcpip.SockOptInt) (int, *tcpip.Error)
@@ -1213,12 +1221,15 @@ func getSockOptIPv6(t *kernel.Task, ep commonEndpoint, name, outLen int) (interf
 			return nil, syserr.ErrInvalidArgument
 		}
 
-		var v tcpip.V6OnlyOption
-		if err := ep.GetSockOpt(&v); err != nil {
+		v, err := ep.GetSockOptBool(tcpip.V6OnlyOption)
+		if err != nil {
 			return nil, syserr.TranslateNetstackError(err)
 		}
-
-		return int32(v), nil
+		var o uint32
+		if v {
+			o = 1
+		}
+		return int32(o), nil
 
 	case linux.IPV6_PATHMTU:
 		t.Kernel().EmitUnimplementedEvent(t)
@@ -1621,7 +1632,7 @@ func setSockOptIPv6(t *kernel.Task, ep commonEndpoint, name int, optVal []byte)
 		}
 
 		v := usermem.ByteOrder.Uint32(optVal)
-		return syserr.TranslateNetstackError(ep.SetSockOpt(tcpip.V6OnlyOption(v)))
+		return syserr.TranslateNetstackError(ep.SetSockOptBool(tcpip.V6OnlyOption, v != 0))
 
 	case linux.IPV6_ADD_MEMBERSHIP,
 		linux.IPV6_DROP_MEMBERSHIP,
diff --git a/pkg/sentry/socket/unix/transport/unix.go b/pkg/sentry/socket/unix/transport/unix.go
index fcba49435..37c7ac3c1 100644
--- a/pkg/sentry/socket/unix/transport/unix.go
+++ b/pkg/sentry/socket/unix/transport/unix.go
@@ -175,6 +175,10 @@ type Endpoint interface {
 	// types.
 	SetSockOpt(opt interface{}) *tcpip.Error
 
+	// SetSockOptBool sets a socket option for simple cases when a value has
+	// the int type.
+	SetSockOptBool(opt tcpip.SockOptBool, v bool) *tcpip.Error
+
 	// SetSockOptInt sets a socket option for simple cases when a value has
 	// the int type.
 	SetSockOptInt(opt tcpip.SockOptInt, v int) *tcpip.Error
@@ -183,6 +187,10 @@ type Endpoint interface {
 	// tcpip.*Option types.
 	GetSockOpt(opt interface{}) *tcpip.Error
 
+	// GetSockOptBool gets a socket option for simple cases when a return
+	// value has the int type.
+	GetSockOptBool(opt tcpip.SockOptBool) (bool, *tcpip.Error)
+
 	// GetSockOptInt gets a socket option for simple cases when a return
 	// value has the int type.
 	GetSockOptInt(opt tcpip.SockOptInt) (int, *tcpip.Error)
@@ -851,10 +859,18 @@ func (e *baseEndpoint) SetSockOpt(opt interface{}) *tcpip.Error {
 	return nil
 }
 
+func (e *baseEndpoint) SetSockOptBool(opt tcpip.SockOptBool, v bool) *tcpip.Error {
+	return nil
+}
+
 func (e *baseEndpoint) SetSockOptInt(opt tcpip.SockOptInt, v int) *tcpip.Error {
 	return nil
 }
 
+func (e *baseEndpoint) GetSockOptBool(opt tcpip.SockOptBool) (bool, *tcpip.Error) {
+	return false, tcpip.ErrUnknownProtocolOption
+}
+
 func (e *baseEndpoint) GetSockOptInt(opt tcpip.SockOptInt) (int, *tcpip.Error) {
 	switch opt {
 	case tcpip.ReceiveQueueSizeOption:
diff --git a/pkg/tcpip/stack/ndp_test.go b/pkg/tcpip/stack/ndp_test.go
index 070d80c8d..e51462a55 100644
--- a/pkg/tcpip/stack/ndp_test.go
+++ b/pkg/tcpip/stack/ndp_test.go
@@ -1701,9 +1701,8 @@ func addrForNewConnection(t *testing.T, s *stack.Stack) tcpip.Address {
 		t.Fatalf("s.NewEndpoint(%d, %d, _): %s", header.UDPProtocolNumber, header.IPv6ProtocolNumber, err)
 	}
 	defer ep.Close()
-	v := tcpip.V6OnlyOption(1)
-	if err := ep.SetSockOpt(v); err != nil {
-		t.Fatalf("SetSockOpt(%+v): %s", v, err)
+	if err := ep.SetSockOptBool(tcpip.V6OnlyOption, true); err != nil {
+		t.Fatalf("SetSockOpt(tcpip.V6OnlyOption, true): %s", err)
 	}
 	if err := ep.Connect(dstAddr); err != nil {
 		t.Fatalf("ep.Connect(%+v): %s", dstAddr, err)
@@ -1728,9 +1727,8 @@ func addrForNewConnectionWithAddr(t *testing.T, s *stack.Stack, addr tcpip.FullA
 		t.Fatalf("s.NewEndpoint(%d, %d, _): %s", header.UDPProtocolNumber, header.IPv6ProtocolNumber, err)
 	}
 	defer ep.Close()
-	v := tcpip.V6OnlyOption(1)
-	if err := ep.SetSockOpt(v); err != nil {
-		t.Fatalf("SetSockOpt(%+v): %s", v, err)
+	if err := ep.SetSockOptBool(tcpip.V6OnlyOption, true); err != nil {
+		t.Fatalf("SetSockOpt(tcpip.V6OnlyOption, true): %s", err)
 	}
 	if err := ep.Bind(addr); err != nil {
 		t.Fatalf("ep.Bind(%+v): %s", addr, err)
@@ -2066,9 +2064,8 @@ func TestAutoGenAddrTimerDeprecation(t *testing.T) {
 		t.Fatalf("s.NewEndpoint(%d, %d, _): %s", header.UDPProtocolNumber, header.IPv6ProtocolNumber, err)
 	}
 	defer ep.Close()
-	v := tcpip.V6OnlyOption(1)
-	if err := ep.SetSockOpt(v); err != nil {
-		t.Fatalf("SetSockOpt(%+v): %s", v, err)
+	if err := ep.SetSockOptBool(tcpip.V6OnlyOption, true); err != nil {
+		t.Fatalf("SetSockOpt(tcpip.V6OnlyOption, true): %s", err)
 	}
 
 	if err := ep.Connect(dstAddr); err != tcpip.ErrNoRoute {
diff --git a/pkg/tcpip/stack/transport_demuxer_test.go b/pkg/tcpip/stack/transport_demuxer_test.go
index 33dbc0536..df5ced887 100644
--- a/pkg/tcpip/stack/transport_demuxer_test.go
+++ b/pkg/tcpip/stack/transport_demuxer_test.go
@@ -61,11 +61,7 @@ func (c *testContext) createV6Endpoint(v6only bool) {
 		c.t.Fatalf("NewEndpoint failed: %v", err)
 	}
 
-	var v tcpip.V6OnlyOption
-	if v6only {
-		v = 1
-	}
-	if err := c.ep.SetSockOpt(v); err != nil {
+	if err := c.ep.SetSockOptBool(tcpip.V6OnlyOption, v6only); err != nil {
 		c.t.Fatalf("SetSockOpt failed: %v", err)
 	}
 }
@@ -201,54 +197,54 @@ func TestDistribution(t *testing.T) {
 			"BindPortReuse",
 			// 5 endpoints that all have reuse set.
 			[]endpointSockopts{
-				endpointSockopts{1, ""},
-				endpointSockopts{1, ""},
-				endpointSockopts{1, ""},
-				endpointSockopts{1, ""},
-				endpointSockopts{1, ""},
+				{1, ""},
+				{1, ""},
+				{1, ""},
+				{1, ""},
+				{1, ""},
 			},
 			map[string][]float64{
 				// Injected packets on dev0 get distributed evenly.
-				"dev0": []float64{0.2, 0.2, 0.2, 0.2, 0.2},
+				"dev0": {0.2, 0.2, 0.2, 0.2, 0.2},
 			},
 		},
 		{
 			"BindToDevice",
 			// 3 endpoints with various bindings.
 			[]endpointSockopts{
-				endpointSockopts{0, "dev0"},
-				endpointSockopts{0, "dev1"},
-				endpointSockopts{0, "dev2"},
+				{0, "dev0"},
+				{0, "dev1"},
+				{0, "dev2"},
 			},
 			map[string][]float64{
 				// Injected packets on dev0 go only to the endpoint bound to dev0.
-				"dev0": []float64{1, 0, 0},
+				"dev0": {1, 0, 0},
 				// Injected packets on dev1 go only to the endpoint bound to dev1.
-				"dev1": []float64{0, 1, 0},
+				"dev1": {0, 1, 0},
 				// Injected packets on dev2 go only to the endpoint bound to dev2.
-				"dev2": []float64{0, 0, 1},
+				"dev2": {0, 0, 1},
 			},
 		},
 		{
 			"ReuseAndBindToDevice",
 			// 6 endpoints with various bindings.
 			[]endpointSockopts{
-				endpointSockopts{1, "dev0"},
-				endpointSockopts{1, "dev0"},
-				endpointSockopts{1, "dev1"},
-				endpointSockopts{1, "dev1"},
-				endpointSockopts{1, "dev1"},
-				endpointSockopts{1, ""},
+				{1, "dev0"},
+				{1, "dev0"},
+				{1, "dev1"},
+				{1, "dev1"},
+				{1, "dev1"},
+				{1, ""},
 			},
 			map[string][]float64{
 				// Injected packets on dev0 get distributed among endpoints bound to
 				// dev0.
-				"dev0": []float64{0.5, 0.5, 0, 0, 0, 0},
+				"dev0": {0.5, 0.5, 0, 0, 0, 0},
 				// Injected packets on dev1 get distributed among endpoints bound to
 				// dev1 or unbound.
-				"dev1": []float64{0, 0, 1. / 3, 1. / 3, 1. / 3, 0},
+				"dev1": {0, 0, 1. / 3, 1. / 3, 1. / 3, 0},
 				// Injected packets on dev999 go only to the unbound.
-				"dev999": []float64{0, 0, 0, 0, 0, 1},
+				"dev999": {0, 0, 0, 0, 0, 1},
 			},
 		},
 	} {
diff --git a/pkg/tcpip/stack/transport_test.go b/pkg/tcpip/stack/transport_test.go
index 095346f0b..f50604a8a 100644
--- a/pkg/tcpip/stack/transport_test.go
+++ b/pkg/tcpip/stack/transport_test.go
@@ -102,11 +102,21 @@ func (*fakeTransportEndpoint) SetSockOpt(interface{}) *tcpip.Error {
 	return tcpip.ErrInvalidEndpointState
 }
 
+// SetSockOptBool sets a socket option. Currently not supported.
+func (*fakeTransportEndpoint) SetSockOptBool(tcpip.SockOptBool, bool) *tcpip.Error {
+	return tcpip.ErrInvalidEndpointState
+}
+
 // SetSockOptInt sets a socket option. Currently not supported.
 func (*fakeTransportEndpoint) SetSockOptInt(tcpip.SockOptInt, int) *tcpip.Error {
 	return tcpip.ErrInvalidEndpointState
 }
 
+// GetSockOptBool implements tcpip.Endpoint.GetSockOptBool.
+func (*fakeTransportEndpoint) GetSockOptBool(opt tcpip.SockOptBool) (bool, *tcpip.Error) {
+	return false, tcpip.ErrUnknownProtocolOption
+}
+
 // GetSockOptInt implements tcpip.Endpoint.GetSockOptInt.
 func (*fakeTransportEndpoint) GetSockOptInt(opt tcpip.SockOptInt) (int, *tcpip.Error) {
 	return -1, tcpip.ErrUnknownProtocolOption
diff --git a/pkg/tcpip/tcpip.go b/pkg/tcpip/tcpip.go
index b172d71b0..1eca76c30 100644
--- a/pkg/tcpip/tcpip.go
+++ b/pkg/tcpip/tcpip.go
@@ -423,6 +423,10 @@ type Endpoint interface {
 	// SetSockOpt sets a socket option. opt should be one of the *Option types.
 	SetSockOpt(opt interface{}) *Error
 
+	// SetSockOptBool sets a socket option, for simple cases where a value
+	// has the bool type.
+	SetSockOptBool(opt SockOptBool, v bool) *Error
+
 	// SetSockOptInt sets a socket option, for simple cases where a value
 	// has the int type.
 	SetSockOptInt(opt SockOptInt, v int) *Error
@@ -431,6 +435,10 @@ type Endpoint interface {
 	// *Option types.
 	GetSockOpt(opt interface{}) *Error
 
+	// GetSockOptBool gets a socket option for simple cases where a return
+	// value has the bool type.
+	GetSockOptBool(SockOptBool) (bool, *Error)
+
 	// GetSockOptInt gets a socket option for simple cases where a return
 	// value has the int type.
 	GetSockOptInt(SockOptInt) (int, *Error)
@@ -488,6 +496,15 @@ type WriteOptions struct {
 	Atomic bool
 }
 
+// SockOptBool represents socket options which values have the bool type.
+type SockOptBool int
+
+const (
+	// V6OnlyOption is used by {G,S}etSockOptBool to specify whether an IPv6
+	// socket is to be restricted to sending and receiving IPv6 packets only.
+	V6OnlyOption SockOptBool = iota
+)
+
 // SockOptInt represents socket options which values have the int type.
 type SockOptInt int
 
@@ -521,10 +538,6 @@ const (
 // the endpoint should be cleared and returned.
 type ErrorOption struct{}
 
-// V6OnlyOption is used by SetSockOpt/GetSockOpt to specify whether an IPv6
-// socket is to be restricted to sending and receiving IPv6 packets only.
-type V6OnlyOption int
-
 // CorkOption is used by SetSockOpt/GetSockOpt to specify if data should be
 // held until segments are full by the TCP transport protocol.
 type CorkOption int
diff --git a/pkg/tcpip/transport/icmp/endpoint.go b/pkg/tcpip/transport/icmp/endpoint.go
index 5816ce49a..c7ce74cdd 100644
--- a/pkg/tcpip/transport/icmp/endpoint.go
+++ b/pkg/tcpip/transport/icmp/endpoint.go
@@ -350,11 +350,21 @@ func (e *endpoint) SetSockOpt(opt interface{}) *tcpip.Error {
 	return nil
 }
 
+// SetSockOptBool sets a socket option. Currently not supported.
+func (e *endpoint) SetSockOptBool(opt tcpip.SockOptBool, v bool) *tcpip.Error {
+	return nil
+}
+
 // SetSockOptInt sets a socket option. Currently not supported.
 func (e *endpoint) SetSockOptInt(opt tcpip.SockOptInt, v int) *tcpip.Error {
 	return nil
 }
 
+// GetSockOptBool implements tcpip.Endpoint.GetSockOptBool.
+func (e *endpoint) GetSockOptBool(opt tcpip.SockOptBool) (bool, *tcpip.Error) {
+	return false, tcpip.ErrUnknownProtocolOption
+}
+
 // GetSockOptInt implements tcpip.Endpoint.GetSockOptInt.
 func (e *endpoint) GetSockOptInt(opt tcpip.SockOptInt) (int, *tcpip.Error) {
 	switch opt {
diff --git a/pkg/tcpip/transport/packet/endpoint.go b/pkg/tcpip/transport/packet/endpoint.go
index 6360ce880..07ffa8aba 100644
--- a/pkg/tcpip/transport/packet/endpoint.go
+++ b/pkg/tcpip/transport/packet/endpoint.go
@@ -247,17 +247,17 @@ func (ep *endpoint) Readiness(mask waiter.EventMask) waiter.EventMask {
 // used with SetSockOpt, and this function always returns
 // tcpip.ErrNotSupported.
 func (ep *endpoint) SetSockOpt(opt interface{}) *tcpip.Error {
-	return tcpip.ErrNotSupported
+	return tcpip.ErrUnknownProtocolOption
 }
 
-// SetSockOptInt implements tcpip.Endpoint.SetSockOptInt.
-func (ep *endpoint) SetSockOptInt(opt tcpip.SockOptInt, v int) *tcpip.Error {
+// SetSockOptBool implements tcpip.Endpoint.SetSockOptBool.
+func (ep *endpoint) SetSockOptBool(opt tcpip.SockOptBool, v bool) *tcpip.Error {
 	return tcpip.ErrUnknownProtocolOption
 }
 
-// GetSockOptInt implements tcpip.Endpoint.GetSockOptInt.
-func (ep *endpoint) GetSockOptInt(opt tcpip.SockOptInt) (int, *tcpip.Error) {
-	return 0, tcpip.ErrNotSupported
+// SetSockOptInt implements tcpip.Endpoint.SetSockOptInt.
+func (ep *endpoint) SetSockOptInt(opt tcpip.SockOptInt, v int) *tcpip.Error {
+	return tcpip.ErrUnknownProtocolOption
 }
 
 // GetSockOpt implements tcpip.Endpoint.GetSockOpt.
@@ -265,6 +265,16 @@ func (ep *endpoint) GetSockOpt(opt interface{}) *tcpip.Error {
 	return tcpip.ErrNotSupported
 }
 
+// GetSockOptBool implements tcpip.Endpoint.GetSockOptBool.
+func (ep *endpoint) GetSockOptBool(opt tcpip.SockOptBool) (bool, *tcpip.Error) {
+	return false, tcpip.ErrNotSupported
+}
+
+// GetSockOptInt implements tcpip.Endpoint.GetSockOptInt.
+func (ep *endpoint) GetSockOptInt(opt tcpip.SockOptInt) (int, *tcpip.Error) {
+	return 0, tcpip.ErrNotSupported
+}
+
 // HandlePacket implements stack.PacketEndpoint.HandlePacket.
 func (ep *endpoint) HandlePacket(nicID tcpip.NICID, localAddr tcpip.LinkAddress, netProto tcpip.NetworkProtocolNumber, pkt tcpip.PacketBuffer) {
 	ep.rcvMu.Lock()
diff --git a/pkg/tcpip/transport/raw/endpoint.go b/pkg/tcpip/transport/raw/endpoint.go
index 0fd9c456a..85f7eb76b 100644
--- a/pkg/tcpip/transport/raw/endpoint.go
+++ b/pkg/tcpip/transport/raw/endpoint.go
@@ -509,11 +509,36 @@ func (e *endpoint) SetSockOpt(opt interface{}) *tcpip.Error {
 	return tcpip.ErrUnknownProtocolOption
 }
 
+// SetSockOptBool implements tcpip.Endpoint.SetSockOptBool.
+func (e *endpoint) SetSockOptBool(opt tcpip.SockOptBool, v bool) *tcpip.Error {
+	return tcpip.ErrUnknownProtocolOption
+}
+
 // SetSockOptInt implements tcpip.Endpoint.SetSockOptInt.
 func (e *endpoint) SetSockOptInt(opt tcpip.SockOptInt, v int) *tcpip.Error {
 	return tcpip.ErrUnknownProtocolOption
 }
 
+// GetSockOpt implements tcpip.Endpoint.GetSockOpt.
+func (e *endpoint) GetSockOpt(opt interface{}) *tcpip.Error {
+	switch o := opt.(type) {
+	case tcpip.ErrorOption:
+		return nil
+
+	case *tcpip.KeepaliveEnabledOption:
+		*o = 0
+		return nil
+
+	default:
+		return tcpip.ErrUnknownProtocolOption
+	}
+}
+
+// GetSockOptBool implements tcpip.Endpoint.GetSockOptBool.
+func (e *endpoint) GetSockOptBool(opt tcpip.SockOptBool) (bool, *tcpip.Error) {
+	return false, tcpip.ErrUnknownProtocolOption
+}
+
 // GetSockOptInt implements tcpip.Endpoint.GetSockOptInt.
 func (e *endpoint) GetSockOptInt(opt tcpip.SockOptInt) (int, *tcpip.Error) {
 	switch opt {
@@ -544,21 +569,6 @@ func (e *endpoint) GetSockOptInt(opt tcpip.SockOptInt) (int, *tcpip.Error) {
 	return -1, tcpip.ErrUnknownProtocolOption
 }
 
-// GetSockOpt implements tcpip.Endpoint.GetSockOpt.
-func (e *endpoint) GetSockOpt(opt interface{}) *tcpip.Error {
-	switch o := opt.(type) {
-	case tcpip.ErrorOption:
-		return nil
-
-	case *tcpip.KeepaliveEnabledOption:
-		*o = 0
-		return nil
-
-	default:
-		return tcpip.ErrUnknownProtocolOption
-	}
-}
-
 // HandlePacket implements stack.RawTransportEndpoint.HandlePacket.
 func (e *endpoint) HandlePacket(route *stack.Route, pkt tcpip.PacketBuffer) {
 	e.rcvMu.Lock()
diff --git a/pkg/tcpip/transport/tcp/dual_stack_test.go b/pkg/tcpip/transport/tcp/dual_stack_test.go
index dfaa4a559..4f361b226 100644
--- a/pkg/tcpip/transport/tcp/dual_stack_test.go
+++ b/pkg/tcpip/transport/tcp/dual_stack_test.go
@@ -391,9 +391,8 @@ func testV4Accept(t *testing.T, c *context.Context) {
 	// Make sure we get the same error when calling the original ep and the
 	// new one. This validates that v4-mapped endpoints are still able to
 	// query the V6Only flag, whereas pure v4 endpoints are not.
-	var v tcpip.V6OnlyOption
-	expected := c.EP.GetSockOpt(&v)
-	if err := nep.GetSockOpt(&v); err != expected {
+	_, expected := c.EP.GetSockOptBool(tcpip.V6OnlyOption)
+	if _, err := nep.GetSockOptBool(tcpip.V6OnlyOption); err != expected {
 		t.Fatalf("GetSockOpt returned unexpected value: got %v, want %v", err, expected)
 	}
 
@@ -531,8 +530,7 @@ func TestV6AcceptOnV6(t *testing.T) {
 
 	// Make sure we can still query the v6 only status of the new endpoint,
 	// that is, that it is in fact a v6 socket.
-	var v tcpip.V6OnlyOption
-	if err := nep.GetSockOpt(&v); err != nil {
+	if _, err := nep.GetSockOptBool(tcpip.V6OnlyOption); err != nil {
 		t.Fatalf("GetSockOpt failed failed: %v", err)
 	}
 
diff --git a/pkg/tcpip/transport/tcp/endpoint.go b/pkg/tcpip/transport/tcp/endpoint.go
index f79154b95..2ac1b6877 100644
--- a/pkg/tcpip/transport/tcp/endpoint.go
+++ b/pkg/tcpip/transport/tcp/endpoint.go
@@ -1145,6 +1145,29 @@ func (e *endpoint) zeroReceiveWindow(scale uint8) bool {
 	return ((e.rcvBufSize - e.rcvBufUsed) >> scale) == 0
 }
 
+// SetSockOptBool sets a socket option.
+func (e *endpoint) SetSockOptBool(opt tcpip.SockOptBool, v bool) *tcpip.Error {
+	switch opt {
+	case tcpip.V6OnlyOption:
+		// We only recognize this option on v6 endpoints.
+		if e.NetProto != header.IPv6ProtocolNumber {
+			return tcpip.ErrInvalidEndpointState
+		}
+
+		e.mu.Lock()
+		defer e.mu.Unlock()
+
+		// We only allow this to be set when we're in the initial state.
+		if e.state != StateInitial {
+			return tcpip.ErrInvalidEndpointState
+		}
+
+		e.v6only = v
+	}
+
+	return nil
+}
+
 // SetSockOptInt sets a socket option.
 func (e *endpoint) SetSockOptInt(opt tcpip.SockOptInt, v int) *tcpip.Error {
 	switch opt {
@@ -1289,23 +1312,6 @@ func (e *endpoint) SetSockOpt(opt interface{}) *tcpip.Error {
 		e.notifyProtocolGoroutine(notifyMSSChanged)
 		return nil
 
-	case tcpip.V6OnlyOption:
-		// We only recognize this option on v6 endpoints.
-		if e.NetProto != header.IPv6ProtocolNumber {
-			return tcpip.ErrInvalidEndpointState
-		}
-
-		e.mu.Lock()
-		defer e.mu.Unlock()
-
-		// We only allow this to be set when we're in the initial state.
-		if e.state != StateInitial {
-			return tcpip.ErrInvalidEndpointState
-		}
-
-		e.v6only = v != 0
-		return nil
-
 	case tcpip.TTLOption:
 		e.mu.Lock()
 		e.ttl = uint8(v)
@@ -1446,6 +1452,25 @@ func (e *endpoint) readyReceiveSize() (int, *tcpip.Error) {
 	return e.rcvBufUsed, nil
 }
 
+// GetSockOptBool implements tcpip.Endpoint.GetSockOptBool.
+func (e *endpoint) GetSockOptBool(opt tcpip.SockOptBool) (bool, *tcpip.Error) {
+	switch opt {
+	case tcpip.V6OnlyOption:
+		// We only recognize this option on v6 endpoints.
+		if e.NetProto != header.IPv6ProtocolNumber {
+			return false, tcpip.ErrUnknownProtocolOption
+		}
+
+		e.mu.Lock()
+		v := e.v6only
+		e.mu.Unlock()
+
+		return v, nil
+	}
+
+	return false, tcpip.ErrUnknownProtocolOption
+}
+
 // GetSockOptInt implements tcpip.Endpoint.GetSockOptInt.
 func (e *endpoint) GetSockOptInt(opt tcpip.SockOptInt) (int, *tcpip.Error) {
 	switch opt {
@@ -1540,22 +1565,6 @@ func (e *endpoint) GetSockOpt(opt interface{}) *tcpip.Error {
 		}
 		return nil
 
-	case *tcpip.V6OnlyOption:
-		// We only recognize this option on v6 endpoints.
-		if e.NetProto != header.IPv6ProtocolNumber {
-			return tcpip.ErrUnknownProtocolOption
-		}
-
-		e.mu.Lock()
-		v := e.v6only
-		e.mu.Unlock()
-
-		*o = 0
-		if v {
-			*o = 1
-		}
-		return nil
-
 	case *tcpip.TTLOption:
 		e.mu.Lock()
 		*o = tcpip.TTLOption(e.ttl)
diff --git a/pkg/tcpip/transport/tcp/tcp_test.go b/pkg/tcpip/transport/tcp/tcp_test.go
index 9d7b0910d..15745ebd4 100644
--- a/pkg/tcpip/transport/tcp/tcp_test.go
+++ b/pkg/tcpip/transport/tcp/tcp_test.go
@@ -4028,12 +4028,12 @@ func TestConnectAvoidsBoundPorts(t *testing.T) {
 												switch network {
 												case "ipv4":
 												case "ipv6":
-													if err := ep.SetSockOpt(tcpip.V6OnlyOption(1)); err != nil {
-														t.Fatalf("SetSockOpt(V6OnlyOption(1)) failed: %v", err)
+													if err := ep.SetSockOptBool(tcpip.V6OnlyOption, true); err != nil {
+														t.Fatalf("SetSockOpt(V6OnlyOption(true)) failed: %v", err)
 													}
 												case "dual":
-													if err := ep.SetSockOpt(tcpip.V6OnlyOption(0)); err != nil {
-														t.Fatalf("SetSockOpt(V6OnlyOption(0)) failed: %v", err)
+													if err := ep.SetSockOptBool(tcpip.V6OnlyOption, false); err != nil {
+														t.Fatalf("SetSockOpt(V6OnlyOption(false)) failed: %v", err)
 													}
 												default:
 													t.Fatalf("unknown network: '%s'", network)
diff --git a/pkg/tcpip/transport/tcp/testing/context/context.go b/pkg/tcpip/transport/tcp/testing/context/context.go
index 50c81aa65..822907998 100644
--- a/pkg/tcpip/transport/tcp/testing/context/context.go
+++ b/pkg/tcpip/transport/tcp/testing/context/context.go
@@ -475,11 +475,7 @@ func (c *Context) CreateV6Endpoint(v6only bool) {
 		c.t.Fatalf("NewEndpoint failed: %v", err)
 	}
 
-	var v tcpip.V6OnlyOption
-	if v6only {
-		v = 1
-	}
-	if err := c.EP.SetSockOpt(v); err != nil {
+	if err := c.EP.SetSockOptBool(tcpip.V6OnlyOption, v6only); err != nil {
 		c.t.Fatalf("SetSockOpt failed failed: %v", err)
 	}
 }
diff --git a/pkg/tcpip/transport/udp/endpoint.go b/pkg/tcpip/transport/udp/endpoint.go
index dae373ea7..1a5ee6317 100644
--- a/pkg/tcpip/transport/udp/endpoint.go
+++ b/pkg/tcpip/transport/udp/endpoint.go
@@ -456,14 +456,9 @@ func (e *endpoint) Peek([][]byte) (int64, tcpip.ControlMessages, *tcpip.Error) {
 	return 0, tcpip.ControlMessages{}, nil
 }
 
-// SetSockOptInt implements tcpip.Endpoint.SetSockOptInt.
-func (e *endpoint) SetSockOptInt(opt tcpip.SockOptInt, v int) *tcpip.Error {
-	return nil
-}
-
-// SetSockOpt implements tcpip.Endpoint.SetSockOpt.
-func (e *endpoint) SetSockOpt(opt interface{}) *tcpip.Error {
-	switch v := opt.(type) {
+// SetSockOptBool implements tcpip.Endpoint.SetSockOptBool.
+func (e *endpoint) SetSockOptBool(opt tcpip.SockOptBool, v bool) *tcpip.Error {
+	switch opt {
 	case tcpip.V6OnlyOption:
 		// We only recognize this option on v6 endpoints.
 		if e.NetProto != header.IPv6ProtocolNumber {
@@ -478,8 +473,20 @@ func (e *endpoint) SetSockOpt(opt interface{}) *tcpip.Error {
 			return tcpip.ErrInvalidEndpointState
 		}
 
-		e.v6only = v != 0
+		e.v6only = v
+	}
+
+	return nil
+}
 
+// SetSockOptInt implements tcpip.Endpoint.SetSockOptInt.
+func (e *endpoint) SetSockOptInt(opt tcpip.SockOptInt, v int) *tcpip.Error {
+	return nil
+}
+
+// SetSockOpt implements tcpip.Endpoint.SetSockOpt.
+func (e *endpoint) SetSockOpt(opt interface{}) *tcpip.Error {
+	switch v := opt.(type) {
 	case tcpip.TTLOption:
 		e.mu.Lock()
 		e.ttl = uint8(v)
@@ -660,6 +667,25 @@ func (e *endpoint) SetSockOpt(opt interface{}) *tcpip.Error {
 	return nil
 }
 
+// GetSockOptBool implements tcpip.Endpoint.GetSockOptBool.
+func (e *endpoint) GetSockOptBool(opt tcpip.SockOptBool) (bool, *tcpip.Error) {
+	switch opt {
+	case tcpip.V6OnlyOption:
+		// We only recognize this option on v6 endpoints.
+		if e.NetProto != header.IPv6ProtocolNumber {
+			return false, tcpip.ErrUnknownProtocolOption
+		}
+
+		e.mu.Lock()
+		v := e.v6only
+		e.mu.Unlock()
+
+		return v, nil
+	}
+
+	return false, tcpip.ErrUnknownProtocolOption
+}
+
 // GetSockOptInt implements tcpip.Endpoint.GetSockOptInt.
 func (e *endpoint) GetSockOptInt(opt tcpip.SockOptInt) (int, *tcpip.Error) {
 	switch opt {
@@ -695,22 +721,6 @@ func (e *endpoint) GetSockOpt(opt interface{}) *tcpip.Error {
 	case tcpip.ErrorOption:
 		return nil
 
-	case *tcpip.V6OnlyOption:
-		// We only recognize this option on v6 endpoints.
-		if e.NetProto != header.IPv6ProtocolNumber {
-			return tcpip.ErrUnknownProtocolOption
-		}
-
-		e.mu.Lock()
-		v := e.v6only
-		e.mu.Unlock()
-
-		*o = 0
-		if v {
-			*o = 1
-		}
-		return nil
-
 	case *tcpip.TTLOption:
 		e.mu.Lock()
 		*o = tcpip.TTLOption(e.ttl)
diff --git a/pkg/tcpip/transport/udp/udp_test.go b/pkg/tcpip/transport/udp/udp_test.go
index 65382b7f1..149fff999 100644
--- a/pkg/tcpip/transport/udp/udp_test.go
+++ b/pkg/tcpip/transport/udp/udp_test.go
@@ -335,7 +335,7 @@ func (c *testContext) createEndpointForFlow(flow testFlow) {
 
 	c.createEndpoint(flow.sockProto())
 	if flow.isV6Only() {
-		if err := c.ep.SetSockOpt(tcpip.V6OnlyOption(1)); err != nil {
+		if err := c.ep.SetSockOptBool(tcpip.V6OnlyOption, true); err != nil {
 			c.t.Fatalf("SetSockOpt failed: %v", err)
 		}
 	} else if flow.isBroadcast() {
-- 
cgit v1.2.3


From 8643933d6e58492cbe9d5c78124873ab40f65feb Mon Sep 17 00:00:00 2001
From: Eyal Soha <eyalsoha@google.com>
Date: Thu, 9 Jan 2020 13:06:24 -0800
Subject: Change BindToDeviceOption to store NICID

This makes it possible to call the sockopt from go even when the NIC has no
name.

PiperOrigin-RevId: 288955236
---
 pkg/sentry/socket/netstack/netstack.go    | 29 ++++++++--
 pkg/tcpip/stack/stack.go                  |  8 +++
 pkg/tcpip/stack/transport_demuxer_test.go | 89 +++++++++++++++----------------
 pkg/tcpip/tcpip.go                        |  2 +-
 pkg/tcpip/transport/tcp/endpoint.go       | 27 ++++------
 pkg/tcpip/transport/tcp/tcp_test.go       | 42 +++++++--------
 pkg/tcpip/transport/udp/endpoint.go       | 27 ++++------
 pkg/tcpip/transport/udp/udp_test.go       | 31 +++++------
 8 files changed, 127 insertions(+), 128 deletions(-)

(limited to 'pkg/tcpip/transport/tcp')

diff --git a/pkg/sentry/socket/netstack/netstack.go b/pkg/sentry/socket/netstack/netstack.go
index 9e0d69046..764f11a6b 100644
--- a/pkg/sentry/socket/netstack/netstack.go
+++ b/pkg/sentry/socket/netstack/netstack.go
@@ -985,13 +985,23 @@ func getSockOptSocket(t *kernel.Task, s socket.Socket, ep commonEndpoint, family
 		if err := ep.GetSockOpt(&v); err != nil {
 			return nil, syserr.TranslateNetstackError(err)
 		}
-		if len(v) == 0 {
+		if v == 0 {
 			return []byte{}, nil
 		}
 		if outLen < linux.IFNAMSIZ {
 			return nil, syserr.ErrInvalidArgument
 		}
-		return append([]byte(v), 0), nil
+		s := t.NetworkContext()
+		if s == nil {
+			return nil, syserr.ErrNoDevice
+		}
+		nic, ok := s.Interfaces()[int32(v)]
+		if !ok {
+			// The NICID no longer indicates a valid interface, probably because that
+			// interface was removed.
+			return nil, syserr.ErrUnknownDevice
+		}
+		return append([]byte(nic.Name), 0), nil
 
 	case linux.SO_BROADCAST:
 		if outLen < sizeOfInt32 {
@@ -1438,7 +1448,20 @@ func setSockOptSocket(t *kernel.Task, s socket.Socket, ep commonEndpoint, name i
 		if n == -1 {
 			n = len(optVal)
 		}
-		return syserr.TranslateNetstackError(ep.SetSockOpt(tcpip.BindToDeviceOption(optVal[:n])))
+		name := string(optVal[:n])
+		if name == "" {
+			return syserr.TranslateNetstackError(ep.SetSockOpt(tcpip.BindToDeviceOption(0)))
+		}
+		s := t.NetworkContext()
+		if s == nil {
+			return syserr.ErrNoDevice
+		}
+		for nicID, nic := range s.Interfaces() {
+			if nic.Name == name {
+				return syserr.TranslateNetstackError(ep.SetSockOpt(tcpip.BindToDeviceOption(nicID)))
+			}
+		}
+		return syserr.ErrUnknownDevice
 
 	case linux.SO_BROADCAST:
 		if len(optVal) < sizeOfInt32 {
diff --git a/pkg/tcpip/stack/stack.go b/pkg/tcpip/stack/stack.go
index e2a2edb2c..41bf9fd9b 100644
--- a/pkg/tcpip/stack/stack.go
+++ b/pkg/tcpip/stack/stack.go
@@ -901,6 +901,14 @@ type NICInfo struct {
 	Context NICContext
 }
 
+// HasNIC returns true if the NICID is defined in the stack.
+func (s *Stack) HasNIC(id tcpip.NICID) bool {
+	s.mu.RLock()
+	_, ok := s.nics[id]
+	s.mu.RUnlock()
+	return ok
+}
+
 // NICInfo returns a map of NICIDs to their associated information.
 func (s *Stack) NICInfo() map[tcpip.NICID]NICInfo {
 	s.mu.RLock()
diff --git a/pkg/tcpip/stack/transport_demuxer_test.go b/pkg/tcpip/stack/transport_demuxer_test.go
index df5ced887..5e9237de9 100644
--- a/pkg/tcpip/stack/transport_demuxer_test.go
+++ b/pkg/tcpip/stack/transport_demuxer_test.go
@@ -41,7 +41,7 @@ const (
 
 type testContext struct {
 	t       *testing.T
-	linkEPs map[string]*channel.Endpoint
+	linkEps map[tcpip.NICID]*channel.Endpoint
 	s       *stack.Stack
 
 	ep tcpip.Endpoint
@@ -66,27 +66,24 @@ func (c *testContext) createV6Endpoint(v6only bool) {
 	}
 }
 
-// newDualTestContextMultiNic creates the testing context and also linkEpNames
-// named NICs.
-func newDualTestContextMultiNic(t *testing.T, mtu uint32, linkEpNames []string) *testContext {
+// newDualTestContextMultiNIC creates the testing context and also linkEpIDs NICs.
+func newDualTestContextMultiNIC(t *testing.T, mtu uint32, linkEpIDs []tcpip.NICID) *testContext {
 	s := stack.New(stack.Options{
 		NetworkProtocols:   []stack.NetworkProtocol{ipv4.NewProtocol(), ipv6.NewProtocol()},
 		TransportProtocols: []stack.TransportProtocol{udp.NewProtocol()}})
-	linkEPs := make(map[string]*channel.Endpoint)
-	for i, linkEpName := range linkEpNames {
-		channelEP := channel.New(256, mtu, "")
-		nicID := tcpip.NICID(i + 1)
-		opts := stack.NICOptions{Name: linkEpName}
-		if err := s.CreateNICWithOptions(nicID, channelEP, opts); err != nil {
-			t.Fatalf("CreateNICWithOptions(_, _, %+v) failed: %v", opts, err)
+	linkEps := make(map[tcpip.NICID]*channel.Endpoint)
+	for _, linkEpID := range linkEpIDs {
+		channelEp := channel.New(256, mtu, "")
+		if err := s.CreateNIC(linkEpID, channelEp); err != nil {
+			t.Fatalf("CreateNIC failed: %v", err)
 		}
-		linkEPs[linkEpName] = channelEP
+		linkEps[linkEpID] = channelEp
 
-		if err := s.AddAddress(nicID, ipv4.ProtocolNumber, stackAddr); err != nil {
+		if err := s.AddAddress(linkEpID, ipv4.ProtocolNumber, stackAddr); err != nil {
 			t.Fatalf("AddAddress IPv4 failed: %v", err)
 		}
 
-		if err := s.AddAddress(nicID, ipv6.ProtocolNumber, stackV6Addr); err != nil {
+		if err := s.AddAddress(linkEpID, ipv6.ProtocolNumber, stackV6Addr); err != nil {
 			t.Fatalf("AddAddress IPv6 failed: %v", err)
 		}
 	}
@@ -105,7 +102,7 @@ func newDualTestContextMultiNic(t *testing.T, mtu uint32, linkEpNames []string)
 	return &testContext{
 		t:       t,
 		s:       s,
-		linkEPs: linkEPs,
+		linkEps: linkEps,
 	}
 }
 
@@ -122,7 +119,7 @@ func newPayload() []byte {
 	return b
 }
 
-func (c *testContext) sendV6Packet(payload []byte, h *headers, linkEpName string) {
+func (c *testContext) sendV6Packet(payload []byte, h *headers, linkEpID tcpip.NICID) {
 	// Allocate a buffer for data and headers.
 	buf := buffer.NewView(header.UDPMinimumSize + header.IPv6MinimumSize + len(payload))
 	copy(buf[len(buf)-len(payload):], payload)
@@ -153,7 +150,7 @@ func (c *testContext) sendV6Packet(payload []byte, h *headers, linkEpName string
 	u.SetChecksum(^u.CalculateChecksum(xsum))
 
 	// Inject packet.
-	c.linkEPs[linkEpName].InjectInbound(ipv6.ProtocolNumber, tcpip.PacketBuffer{
+	c.linkEps[linkEpID].InjectInbound(ipv6.ProtocolNumber, tcpip.PacketBuffer{
 		Data: buf.ToVectorisedView(),
 	})
 }
@@ -183,7 +180,7 @@ func TestTransportDemuxerRegister(t *testing.T) {
 func TestDistribution(t *testing.T) {
 	type endpointSockopts struct {
 		reuse        int
-		bindToDevice string
+		bindToDevice tcpip.NICID
 	}
 	for _, test := range []struct {
 		name string
@@ -191,71 +188,71 @@ func TestDistribution(t *testing.T) {
 		endpoints []endpointSockopts
 		// wantedDistribution is the wanted ratio of packets received on each
 		// endpoint for each NIC on which packets are injected.
-		wantedDistributions map[string][]float64
+		wantedDistributions map[tcpip.NICID][]float64
 	}{
 		{
 			"BindPortReuse",
 			// 5 endpoints that all have reuse set.
 			[]endpointSockopts{
-				{1, ""},
-				{1, ""},
-				{1, ""},
-				{1, ""},
-				{1, ""},
+				{1, 0},
+				{1, 0},
+				{1, 0},
+				{1, 0},
+				{1, 0},
 			},
-			map[string][]float64{
+			map[tcpip.NICID][]float64{
 				// Injected packets on dev0 get distributed evenly.
-				"dev0": {0.2, 0.2, 0.2, 0.2, 0.2},
+				1: {0.2, 0.2, 0.2, 0.2, 0.2},
 			},
 		},
 		{
 			"BindToDevice",
 			// 3 endpoints with various bindings.
 			[]endpointSockopts{
-				{0, "dev0"},
-				{0, "dev1"},
-				{0, "dev2"},
+				{0, 1},
+				{0, 2},
+				{0, 3},
 			},
-			map[string][]float64{
+			map[tcpip.NICID][]float64{
 				// Injected packets on dev0 go only to the endpoint bound to dev0.
-				"dev0": {1, 0, 0},
+				1: {1, 0, 0},
 				// Injected packets on dev1 go only to the endpoint bound to dev1.
-				"dev1": {0, 1, 0},
+				2: {0, 1, 0},
 				// Injected packets on dev2 go only to the endpoint bound to dev2.
-				"dev2": {0, 0, 1},
+				3: {0, 0, 1},
 			},
 		},
 		{
 			"ReuseAndBindToDevice",
 			// 6 endpoints with various bindings.
 			[]endpointSockopts{
-				{1, "dev0"},
-				{1, "dev0"},
-				{1, "dev1"},
-				{1, "dev1"},
-				{1, "dev1"},
-				{1, ""},
+				{1, 1},
+				{1, 1},
+				{1, 2},
+				{1, 2},
+				{1, 2},
+				{1, 0},
 			},
-			map[string][]float64{
+			map[tcpip.NICID][]float64{
 				// Injected packets on dev0 get distributed among endpoints bound to
 				// dev0.
-				"dev0": {0.5, 0.5, 0, 0, 0, 0},
+				1: {0.5, 0.5, 0, 0, 0, 0},
 				// Injected packets on dev1 get distributed among endpoints bound to
 				// dev1 or unbound.
-				"dev1": {0, 0, 1. / 3, 1. / 3, 1. / 3, 0},
+				2: {0, 0, 1. / 3, 1. / 3, 1. / 3, 0},
 				// Injected packets on dev999 go only to the unbound.
-				"dev999": {0, 0, 0, 0, 0, 1},
+				1000: {0, 0, 0, 0, 0, 1},
 			},
 		},
 	} {
 		t.Run(test.name, func(t *testing.T) {
 			for device, wantedDistribution := range test.wantedDistributions {
-				t.Run(device, func(t *testing.T) {
-					var devices []string
+				t.Run(string(device), func(t *testing.T) {
+					var devices []tcpip.NICID
 					for d := range test.wantedDistributions {
 						devices = append(devices, d)
 					}
-					c := newDualTestContextMultiNic(t, defaultMTU, devices)
+					c := newDualTestContextMultiNIC(t, defaultMTU, devices)
 					defer c.cleanup()
 
 					c.createV6Endpoint(false)
diff --git a/pkg/tcpip/tcpip.go b/pkg/tcpip/tcpip.go
index 1eca76c30..72b5ce179 100644
--- a/pkg/tcpip/tcpip.go
+++ b/pkg/tcpip/tcpip.go
@@ -552,7 +552,7 @@ type ReusePortOption int
 
 // BindToDeviceOption is used by SetSockOpt/GetSockOpt to specify that sockets
 // should bind only on a specific NIC.
-type BindToDeviceOption string
+type BindToDeviceOption NICID
 
 // QuickAckOption is stubbed out in SetSockOpt/GetSockOpt.
 type QuickAckOption int
diff --git a/pkg/tcpip/transport/tcp/endpoint.go b/pkg/tcpip/transport/tcp/endpoint.go
index 2ac1b6877..920b24975 100644
--- a/pkg/tcpip/transport/tcp/endpoint.go
+++ b/pkg/tcpip/transport/tcp/endpoint.go
@@ -1279,19 +1279,14 @@ func (e *endpoint) SetSockOpt(opt interface{}) *tcpip.Error {
 		return nil
 
 	case tcpip.BindToDeviceOption:
-		e.mu.Lock()
-		defer e.mu.Unlock()
-		if v == "" {
-			e.bindToDevice = 0
-			return nil
-		}
-		for nicID, nic := range e.stack.NICInfo() {
-			if nic.Name == string(v) {
-				e.bindToDevice = nicID
-				return nil
-			}
+		id := tcpip.NICID(v)
+		if id != 0 && !e.stack.HasNIC(id) {
+			return tcpip.ErrUnknownDevice
 		}
-		return tcpip.ErrUnknownDevice
+		e.mu.Lock()
+		e.bindToDevice = id
+		e.mu.Unlock()
+		return nil
 
 	case tcpip.QuickAckOption:
 		if v == 0 {
@@ -1550,12 +1545,8 @@ func (e *endpoint) GetSockOpt(opt interface{}) *tcpip.Error {
 
 	case *tcpip.BindToDeviceOption:
 		e.mu.RLock()
-		defer e.mu.RUnlock()
-		if nic, ok := e.stack.NICInfo()[e.bindToDevice]; ok {
-			*o = tcpip.BindToDeviceOption(nic.Name)
-			return nil
-		}
-		*o = ""
+		*o = tcpip.BindToDeviceOption(e.bindToDevice)
+		e.mu.RUnlock()
 		return nil
 
 	case *tcpip.QuickAckOption:
diff --git a/pkg/tcpip/transport/tcp/tcp_test.go b/pkg/tcpip/transport/tcp/tcp_test.go
index 15745ebd4..1aa0733d0 100644
--- a/pkg/tcpip/transport/tcp/tcp_test.go
+++ b/pkg/tcpip/transport/tcp/tcp_test.go
@@ -1083,12 +1083,12 @@ func TestTrafficClassV6(t *testing.T) {
 func TestConnectBindToDevice(t *testing.T) {
 	for _, test := range []struct {
 		name   string
-		device string
+		device tcpip.NICID
 		want   tcp.EndpointState
 	}{
-		{"RightDevice", "nic1", tcp.StateEstablished},
-		{"WrongDevice", "nic2", tcp.StateSynSent},
-		{"AnyDevice", "", tcp.StateEstablished},
+		{"RightDevice", 1, tcp.StateEstablished},
+		{"WrongDevice", 2, tcp.StateSynSent},
+		{"AnyDevice", 0, tcp.StateEstablished},
 	} {
 		t.Run(test.name, func(t *testing.T) {
 			c := context.New(t, defaultMTU)
@@ -3794,47 +3794,41 @@ func TestBindToDeviceOption(t *testing.T) {
 	}
 	defer ep.Close()
 
-	opts := stack.NICOptions{Name: "my_device"}
-	if err := s.CreateNICWithOptions(321, loopback.New(), opts); err != nil {
-		t.Errorf("CreateNICWithOptions(_, _, %+v) failed: %v", opts, err)
-	}
-
-	// Make an nameless NIC.
-	if err := s.CreateNIC(54321, loopback.New()); err != nil {
+	if err := s.CreateNIC(321, loopback.New()); err != nil {
 		t.Errorf("CreateNIC failed: %v", err)
 	}
 
-	// strPtr is used instead of taking the address of string literals, which is
+	// nicIDPtr is used instead of taking the address of NICID literals, which is
 	// a compiler error.
-	strPtr := func(s string) *string {
+	nicIDPtr := func(s tcpip.NICID) *tcpip.NICID {
 		return &s
 	}
 
 	testActions := []struct {
 		name                 string
-		setBindToDevice      *string
+		setBindToDevice      *tcpip.NICID
 		setBindToDeviceError *tcpip.Error
 		getBindToDevice      tcpip.BindToDeviceOption
 	}{
-		{"GetDefaultValue", nil, nil, ""},
-		{"BindToNonExistent", strPtr("non_existent_device"), tcpip.ErrUnknownDevice, ""},
-		{"BindToExistent", strPtr("my_device"), nil, "my_device"},
-		{"UnbindToDevice", strPtr(""), nil, ""},
+		{"GetDefaultValue", nil, nil, 0},
+		{"BindToNonExistent", nicIDPtr(999), tcpip.ErrUnknownDevice, 0},
+		{"BindToExistent", nicIDPtr(321), nil, 321},
+		{"UnbindToDevice", nicIDPtr(0), nil, 0},
 	}
 	for _, testAction := range testActions {
 		t.Run(testAction.name, func(t *testing.T) {
 			if testAction.setBindToDevice != nil {
 				bindToDevice := tcpip.BindToDeviceOption(*testAction.setBindToDevice)
-				if got, want := ep.SetSockOpt(bindToDevice), testAction.setBindToDeviceError; got != want {
-					t.Errorf("SetSockOpt(%v) got %v, want %v", bindToDevice, got, want)
+				if gotErr, wantErr := ep.SetSockOpt(bindToDevice), testAction.setBindToDeviceError; gotErr != wantErr {
+					t.Errorf("SetSockOpt(%v) got %v, want %v", bindToDevice, gotErr, wantErr)
 				}
 			}
-			bindToDevice := tcpip.BindToDeviceOption("to be modified by GetSockOpt")
-			if ep.GetSockOpt(&bindToDevice) != nil {
-				t.Errorf("GetSockOpt got %v, want %v", ep.GetSockOpt(&bindToDevice), nil)
+			bindToDevice := tcpip.BindToDeviceOption(88888)
+			if err := ep.GetSockOpt(&bindToDevice); err != nil {
+				t.Errorf("GetSockOpt got %v, want %v", err, nil)
 			}
 			if got, want := bindToDevice, testAction.getBindToDevice; got != want {
-				t.Errorf("bindToDevice got %q, want %q", got, want)
+				t.Errorf("bindToDevice got %d, want %d", got, want)
 			}
 		})
 	}
diff --git a/pkg/tcpip/transport/udp/endpoint.go b/pkg/tcpip/transport/udp/endpoint.go
index 1a5ee6317..864dc8733 100644
--- a/pkg/tcpip/transport/udp/endpoint.go
+++ b/pkg/tcpip/transport/udp/endpoint.go
@@ -631,19 +631,14 @@ func (e *endpoint) SetSockOpt(opt interface{}) *tcpip.Error {
 		e.mu.Unlock()
 
 	case tcpip.BindToDeviceOption:
-		e.mu.Lock()
-		defer e.mu.Unlock()
-		if v == "" {
-			e.bindToDevice = 0
-			return nil
-		}
-		for nicID, nic := range e.stack.NICInfo() {
-			if nic.Name == string(v) {
-				e.bindToDevice = nicID
-				return nil
-			}
+		id := tcpip.NICID(v)
+		if id != 0 && !e.stack.HasNIC(id) {
+			return tcpip.ErrUnknownDevice
 		}
-		return tcpip.ErrUnknownDevice
+		e.mu.Lock()
+		e.bindToDevice = id
+		e.mu.Unlock()
+		return nil
 
 	case tcpip.BroadcastOption:
 		e.mu.Lock()
@@ -767,12 +762,8 @@ func (e *endpoint) GetSockOpt(opt interface{}) *tcpip.Error {
 
 	case *tcpip.BindToDeviceOption:
 		e.mu.RLock()
-		defer e.mu.RUnlock()
-		if nic, ok := e.stack.NICInfo()[e.bindToDevice]; ok {
-			*o = tcpip.BindToDeviceOption(nic.Name)
-			return nil
-		}
-		*o = tcpip.BindToDeviceOption("")
+		*o = tcpip.BindToDeviceOption(e.bindToDevice)
+		e.mu.RUnlock()
 		return nil
 
 	case *tcpip.KeepaliveEnabledOption:
diff --git a/pkg/tcpip/transport/udp/udp_test.go b/pkg/tcpip/transport/udp/udp_test.go
index 149fff999..0a82bc4fa 100644
--- a/pkg/tcpip/transport/udp/udp_test.go
+++ b/pkg/tcpip/transport/udp/udp_test.go
@@ -513,42 +513,37 @@ func TestBindToDeviceOption(t *testing.T) {
 		t.Errorf("CreateNICWithOptions(_, _, %+v) failed: %v", opts, err)
 	}
 
-	// Make an nameless NIC.
-	if err := s.CreateNIC(54321, loopback.New()); err != nil {
-		t.Errorf("CreateNIC failed: %v", err)
-	}
-
-	// strPtr is used instead of taking the address of string literals, which is
+	// nicIDPtr is used instead of taking the address of NICID literals, which is
 	// a compiler error.
-	strPtr := func(s string) *string {
+	nicIDPtr := func(s tcpip.NICID) *tcpip.NICID {
 		return &s
 	}
 
 	testActions := []struct {
 		name                 string
-		setBindToDevice      *string
+		setBindToDevice      *tcpip.NICID
 		setBindToDeviceError *tcpip.Error
 		getBindToDevice      tcpip.BindToDeviceOption
 	}{
-		{"GetDefaultValue", nil, nil, ""},
-		{"BindToNonExistent", strPtr("non_existent_device"), tcpip.ErrUnknownDevice, ""},
-		{"BindToExistent", strPtr("my_device"), nil, "my_device"},
-		{"UnbindToDevice", strPtr(""), nil, ""},
+		{"GetDefaultValue", nil, nil, 0},
+		{"BindToNonExistent", nicIDPtr(999), tcpip.ErrUnknownDevice, 0},
+		{"BindToExistent", nicIDPtr(321), nil, 321},
+		{"UnbindToDevice", nicIDPtr(0), nil, 0},
 	}
 	for _, testAction := range testActions {
 		t.Run(testAction.name, func(t *testing.T) {
 			if testAction.setBindToDevice != nil {
 				bindToDevice := tcpip.BindToDeviceOption(*testAction.setBindToDevice)
-				if got, want := ep.SetSockOpt(bindToDevice), testAction.setBindToDeviceError; got != want {
-					t.Errorf("SetSockOpt(%v) got %v, want %v", bindToDevice, got, want)
+				if gotErr, wantErr := ep.SetSockOpt(bindToDevice), testAction.setBindToDeviceError; gotErr != wantErr {
+					t.Errorf("SetSockOpt(%v) got %v, want %v", bindToDevice, gotErr, wantErr)
 				}
 			}
-			bindToDevice := tcpip.BindToDeviceOption("to be modified by GetSockOpt")
-			if ep.GetSockOpt(&bindToDevice) != nil {
-				t.Errorf("GetSockOpt got %v, want %v", ep.GetSockOpt(&bindToDevice), nil)
+			bindToDevice := tcpip.BindToDeviceOption(88888)
+			if err := ep.GetSockOpt(&bindToDevice); err != nil {
+				t.Errorf("GetSockOpt got %v, want %v", err, nil)
 			}
 			if got, want := bindToDevice, testAction.getBindToDevice; got != want {
-				t.Errorf("bindToDevice got %q, want %q", got, want)
+				t.Errorf("bindToDevice got %d, want %d", got, want)
 			}
 		})
 	}
-- 
cgit v1.2.3


From 27500d529f7fb87eef8812278fd1bbca67bcba72 Mon Sep 17 00:00:00 2001
From: Ian Gudger <igudger@google.com>
Date: Thu, 9 Jan 2020 22:00:42 -0800
Subject: New sync package.

* Rename syncutil to sync.
* Add aliases to sync types.
* Replace existing usage of standard library sync package.

This will make it easier to swap out synchronization primitives. For example,
this will allow us to use primitives from github.com/sasha-s/go-deadlock to
check for lock ordering violations.

Updates #1472

PiperOrigin-RevId: 289033387
---
 pkg/amutex/BUILD                                   |   1 +
 pkg/amutex/amutex_test.go                          |   3 +-
 pkg/atomicbitops/BUILD                             |   1 +
 pkg/atomicbitops/atomic_bitops_test.go             |   3 +-
 pkg/compressio/BUILD                               |   5 +-
 pkg/compressio/compressio.go                       |   2 +-
 pkg/control/server/BUILD                           |   1 +
 pkg/control/server/server.go                       |   2 +-
 pkg/eventchannel/BUILD                             |   2 +
 pkg/eventchannel/event.go                          |   2 +-
 pkg/eventchannel/event_test.go                     |   2 +-
 pkg/fdchannel/BUILD                                |   1 +
 pkg/fdchannel/fdchannel_test.go                    |   3 +-
 pkg/fdnotifier/BUILD                               |   1 +
 pkg/fdnotifier/fdnotifier.go                       |   2 +-
 pkg/flipcall/BUILD                                 |   3 +-
 pkg/flipcall/flipcall_example_test.go              |   3 +-
 pkg/flipcall/flipcall_test.go                      |   3 +-
 pkg/flipcall/flipcall_unsafe.go                    |  10 +-
 pkg/gate/BUILD                                     |   1 +
 pkg/gate/gate_test.go                              |   2 +-
 pkg/linewriter/BUILD                               |   1 +
 pkg/linewriter/linewriter.go                       |   3 +-
 pkg/log/BUILD                                      |   5 +-
 pkg/log/log.go                                     |   2 +-
 pkg/metric/BUILD                                   |   1 +
 pkg/metric/metric.go                               |   2 +-
 pkg/p9/BUILD                                       |   1 +
 pkg/p9/client.go                                   |   2 +-
 pkg/p9/p9test/BUILD                                |   2 +
 pkg/p9/p9test/client_test.go                       |   2 +-
 pkg/p9/p9test/p9test.go                            |   2 +-
 pkg/p9/path_tree.go                                |   3 +-
 pkg/p9/pool.go                                     |   2 +-
 pkg/p9/server.go                                   |   2 +-
 pkg/p9/transport.go                                |   2 +-
 pkg/procid/BUILD                                   |   2 +
 pkg/procid/procid_test.go                          |   3 +-
 pkg/rand/BUILD                                     |   5 +-
 pkg/rand/rand_linux.go                             |   2 +-
 pkg/refs/BUILD                                     |   2 +
 pkg/refs/refcounter.go                             |   2 +-
 pkg/refs/refcounter_test.go                        |   3 +-
 pkg/sentry/arch/BUILD                              |   1 +
 pkg/sentry/arch/arch_x86.go                        |   2 +-
 pkg/sentry/control/BUILD                           |   1 +
 pkg/sentry/control/pprof.go                        |   2 +-
 pkg/sentry/device/BUILD                            |   5 +-
 pkg/sentry/device/device.go                        |   2 +-
 pkg/sentry/fs/BUILD                                |   3 +-
 pkg/sentry/fs/copy_up.go                           |   2 +-
 pkg/sentry/fs/copy_up_test.go                      |   2 +-
 pkg/sentry/fs/dirent.go                            |   2 +-
 pkg/sentry/fs/dirent_cache.go                      |   3 +-
 pkg/sentry/fs/dirent_cache_limiter.go              |   3 +-
 pkg/sentry/fs/fdpipe/BUILD                         |   1 +
 pkg/sentry/fs/fdpipe/pipe.go                       |   2 +-
 pkg/sentry/fs/fdpipe/pipe_state.go                 |   2 +-
 pkg/sentry/fs/file.go                              |   2 +-
 pkg/sentry/fs/file_overlay.go                      |   2 +-
 pkg/sentry/fs/filesystems.go                       |   2 +-
 pkg/sentry/fs/fs.go                                |   3 +-
 pkg/sentry/fs/fsutil/BUILD                         |   1 +
 pkg/sentry/fs/fsutil/host_file_mapper.go           |   2 +-
 pkg/sentry/fs/fsutil/host_mappable.go              |   2 +-
 pkg/sentry/fs/fsutil/inode.go                      |   3 +-
 pkg/sentry/fs/fsutil/inode_cached.go               |   2 +-
 pkg/sentry/fs/gofer/BUILD                          |   1 +
 pkg/sentry/fs/gofer/inode.go                       |   2 +-
 pkg/sentry/fs/gofer/session.go                     |   2 +-
 pkg/sentry/fs/host/BUILD                           |   1 +
 pkg/sentry/fs/host/inode.go                        |   2 +-
 pkg/sentry/fs/host/socket.go                       |   2 +-
 pkg/sentry/fs/host/tty.go                          |   3 +-
 pkg/sentry/fs/inode.go                             |   3 +-
 pkg/sentry/fs/inode_inotify.go                     |   3 +-
 pkg/sentry/fs/inotify.go                           |   2 +-
 pkg/sentry/fs/inotify_watch.go                     |   2 +-
 pkg/sentry/fs/lock/BUILD                           |   1 +
 pkg/sentry/fs/lock/lock.go                         |   2 +-
 pkg/sentry/fs/mounts.go                            |   2 +-
 pkg/sentry/fs/overlay.go                           |   5 +-
 pkg/sentry/fs/proc/BUILD                           |   1 +
 pkg/sentry/fs/proc/seqfile/BUILD                   |   1 +
 pkg/sentry/fs/proc/seqfile/seqfile.go              |   2 +-
 pkg/sentry/fs/proc/sys_net.go                      |   2 +-
 pkg/sentry/fs/ramfs/BUILD                          |   1 +
 pkg/sentry/fs/ramfs/dir.go                         |   2 +-
 pkg/sentry/fs/restore.go                           |   2 +-
 pkg/sentry/fs/tmpfs/BUILD                          |   1 +
 pkg/sentry/fs/tmpfs/inode_file.go                  |   2 +-
 pkg/sentry/fs/tty/BUILD                            |   1 +
 pkg/sentry/fs/tty/dir.go                           |   2 +-
 pkg/sentry/fs/tty/line_discipline.go               |   2 +-
 pkg/sentry/fs/tty/queue.go                         |   3 +-
 pkg/sentry/fsimpl/ext/BUILD                        |   1 +
 pkg/sentry/fsimpl/ext/directory.go                 |   3 +-
 pkg/sentry/fsimpl/ext/filesystem.go                |   2 +-
 pkg/sentry/fsimpl/ext/regular_file.go              |   2 +-
 pkg/sentry/fsimpl/kernfs/BUILD                     |   2 +
 pkg/sentry/fsimpl/kernfs/inode_impl_util.go        |   2 +-
 pkg/sentry/fsimpl/kernfs/kernfs.go                 |   2 +-
 pkg/sentry/fsimpl/kernfs/kernfs_test.go            |   2 +-
 pkg/sentry/fsimpl/tmpfs/BUILD                      |   1 +
 pkg/sentry/fsimpl/tmpfs/regular_file.go            |   2 +-
 pkg/sentry/fsimpl/tmpfs/tmpfs.go                   |   2 +-
 pkg/sentry/kernel/BUILD                            |   5 +-
 pkg/sentry/kernel/abstract_socket_namespace.go     |   2 +-
 pkg/sentry/kernel/auth/BUILD                       |   3 +-
 pkg/sentry/kernel/auth/user_namespace.go           |   2 +-
 pkg/sentry/kernel/epoll/BUILD                      |   1 +
 pkg/sentry/kernel/epoll/epoll.go                   |   2 +-
 pkg/sentry/kernel/eventfd/BUILD                    |   1 +
 pkg/sentry/kernel/eventfd/eventfd.go               |   2 +-
 pkg/sentry/kernel/fasync/BUILD                     |   1 +
 pkg/sentry/kernel/fasync/fasync.go                 |   3 +-
 pkg/sentry/kernel/fd_table.go                      |   2 +-
 pkg/sentry/kernel/fd_table_test.go                 |   2 +-
 pkg/sentry/kernel/fs_context.go                    |   2 +-
 pkg/sentry/kernel/futex/BUILD                      |   8 +-
 pkg/sentry/kernel/futex/futex.go                   |   3 +-
 pkg/sentry/kernel/futex/futex_test.go              |   2 +-
 pkg/sentry/kernel/kernel.go                        |   2 +-
 pkg/sentry/kernel/memevent/BUILD                   |   1 +
 pkg/sentry/kernel/memevent/memory_events.go        |   2 +-
 pkg/sentry/kernel/pipe/BUILD                       |   1 +
 pkg/sentry/kernel/pipe/buffer.go                   |   2 +-
 pkg/sentry/kernel/pipe/node.go                     |   3 +-
 pkg/sentry/kernel/pipe/pipe.go                     |   2 +-
 pkg/sentry/kernel/pipe/pipe_util.go                |   2 +-
 pkg/sentry/kernel/pipe/vfs.go                      |   3 +-
 pkg/sentry/kernel/semaphore/BUILD                  |   1 +
 pkg/sentry/kernel/semaphore/semaphore.go           |   2 +-
 pkg/sentry/kernel/shm/BUILD                        |   1 +
 pkg/sentry/kernel/shm/shm.go                       |   2 +-
 pkg/sentry/kernel/signal_handlers.go               |   3 +-
 pkg/sentry/kernel/signalfd/BUILD                   |   1 +
 pkg/sentry/kernel/signalfd/signalfd.go             |   3 +-
 pkg/sentry/kernel/syscalls.go                      |   2 +-
 pkg/sentry/kernel/syslog.go                        |   3 +-
 pkg/sentry/kernel/task.go                          |   5 +-
 pkg/sentry/kernel/thread_group.go                  |   2 +-
 pkg/sentry/kernel/threads.go                       |   2 +-
 pkg/sentry/kernel/time/BUILD                       |   1 +
 pkg/sentry/kernel/time/time.go                     |   2 +-
 pkg/sentry/kernel/timekeeper.go                    |   2 +-
 pkg/sentry/kernel/tty.go                           |   2 +-
 pkg/sentry/kernel/uts_namespace.go                 |   3 +-
 pkg/sentry/limits/BUILD                            |   1 +
 pkg/sentry/limits/limits.go                        |   3 +-
 pkg/sentry/mm/BUILD                                |   2 +-
 pkg/sentry/mm/aio_context.go                       |   3 +-
 pkg/sentry/mm/mm.go                                |   8 +-
 pkg/sentry/pgalloc/BUILD                           |   1 +
 pkg/sentry/pgalloc/pgalloc.go                      |   2 +-
 pkg/sentry/platform/interrupt/BUILD                |   1 +
 pkg/sentry/platform/interrupt/interrupt.go         |   3 +-
 pkg/sentry/platform/kvm/BUILD                      |   1 +
 pkg/sentry/platform/kvm/address_space.go           |   2 +-
 pkg/sentry/platform/kvm/bluepill_arm64_unsafe.go   |   2 -
 pkg/sentry/platform/kvm/kvm.go                     |   2 +-
 pkg/sentry/platform/kvm/machine.go                 |   2 +-
 pkg/sentry/platform/ptrace/BUILD                   |   1 +
 pkg/sentry/platform/ptrace/ptrace.go               |   2 +-
 pkg/sentry/platform/ptrace/subprocess.go           |   2 +-
 .../platform/ptrace/subprocess_linux_unsafe.go     |   2 +-
 pkg/sentry/platform/ring0/defs.go                  |   2 +-
 pkg/sentry/platform/ring0/defs_amd64.go            |   1 +
 pkg/sentry/platform/ring0/defs_arm64.go            |   1 +
 pkg/sentry/platform/ring0/pagetables/BUILD         |   5 +-
 pkg/sentry/platform/ring0/pagetables/pcids_x86.go  |   2 +-
 pkg/sentry/socket/netlink/BUILD                    |   1 +
 pkg/sentry/socket/netlink/port/BUILD               |   1 +
 pkg/sentry/socket/netlink/port/port.go             |   3 +-
 pkg/sentry/socket/netlink/socket.go                |   2 +-
 pkg/sentry/socket/netstack/BUILD                   |   1 +
 pkg/sentry/socket/netstack/netstack.go             |   2 +-
 pkg/sentry/socket/rpcinet/conn/BUILD               |   1 +
 pkg/sentry/socket/rpcinet/conn/conn.go             |   2 +-
 pkg/sentry/socket/rpcinet/notifier/BUILD           |   1 +
 pkg/sentry/socket/rpcinet/notifier/notifier.go     |   2 +-
 pkg/sentry/socket/unix/transport/BUILD             |   1 +
 pkg/sentry/socket/unix/transport/connectioned.go   |   3 +-
 pkg/sentry/socket/unix/transport/queue.go          |   3 +-
 pkg/sentry/socket/unix/transport/unix.go           |   2 +-
 pkg/sentry/syscalls/linux/BUILD                    |   1 +
 pkg/sentry/syscalls/linux/error.go                 |   2 +-
 pkg/sentry/time/BUILD                              |   4 +-
 pkg/sentry/time/calibrated_clock.go                |   2 +-
 pkg/sentry/usage/BUILD                             |   1 +
 pkg/sentry/usage/memory.go                         |   2 +-
 pkg/sentry/vfs/BUILD                               |   3 +-
 pkg/sentry/vfs/dentry.go                           |   2 +-
 pkg/sentry/vfs/file_description_impl_util.go       |   2 +-
 pkg/sentry/vfs/mount_test.go                       |   3 +-
 pkg/sentry/vfs/mount_unsafe.go                     |   4 +-
 pkg/sentry/vfs/pathname.go                         |   3 +-
 pkg/sentry/vfs/resolving_path.go                   |   2 +-
 pkg/sentry/vfs/vfs.go                              |   2 +-
 pkg/sentry/watchdog/BUILD                          |   1 +
 pkg/sentry/watchdog/watchdog.go                    |   2 +-
 pkg/sync/BUILD                                     |  53 +++++++
 pkg/sync/LICENSE                                   |  27 ++++
 pkg/sync/README.md                                 |   5 +
 pkg/sync/aliases.go                                |  37 +++++
 pkg/sync/atomicptr_unsafe.go                       |  47 +++++++
 pkg/sync/atomicptrtest/BUILD                       |  29 ++++
 pkg/sync/atomicptrtest/atomicptr_test.go           |  31 +++++
 pkg/sync/downgradable_rwmutex_test.go              | 150 ++++++++++++++++++++
 pkg/sync/downgradable_rwmutex_unsafe.go            | 146 ++++++++++++++++++++
 pkg/sync/memmove_unsafe.go                         |  28 ++++
 pkg/sync/norace_unsafe.go                          |  35 +++++
 pkg/sync/race_unsafe.go                            |  41 ++++++
 pkg/sync/seqatomic_unsafe.go                       |  72 ++++++++++
 pkg/sync/seqatomictest/BUILD                       |  33 +++++
 pkg/sync/seqatomictest/seqatomic_test.go           | 132 ++++++++++++++++++
 pkg/sync/seqcount.go                               | 149 ++++++++++++++++++++
 pkg/sync/seqcount_test.go                          | 153 +++++++++++++++++++++
 pkg/sync/syncutil.go                               |   7 +
 pkg/syncutil/BUILD                                 |  52 -------
 pkg/syncutil/LICENSE                               |  27 ----
 pkg/syncutil/README.md                             |   5 -
 pkg/syncutil/atomicptr_unsafe.go                   |  47 -------
 pkg/syncutil/atomicptrtest/BUILD                   |  29 ----
 pkg/syncutil/atomicptrtest/atomicptr_test.go       |  31 -----
 pkg/syncutil/downgradable_rwmutex_test.go          | 150 --------------------
 pkg/syncutil/downgradable_rwmutex_unsafe.go        | 146 --------------------
 pkg/syncutil/memmove_unsafe.go                     |  28 ----
 pkg/syncutil/norace_unsafe.go                      |  35 -----
 pkg/syncutil/race_unsafe.go                        |  41 ------
 pkg/syncutil/seqatomic_unsafe.go                   |  72 ----------
 pkg/syncutil/seqatomictest/BUILD                   |  35 -----
 pkg/syncutil/seqatomictest/seqatomic_test.go       | 132 ------------------
 pkg/syncutil/seqcount.go                           | 149 --------------------
 pkg/syncutil/seqcount_test.go                      | 153 ---------------------
 pkg/syncutil/syncutil.go                           |   7 -
 pkg/tcpip/BUILD                                    |   1 +
 pkg/tcpip/adapters/gonet/BUILD                     |   1 +
 pkg/tcpip/adapters/gonet/gonet.go                  |   2 +-
 pkg/tcpip/link/fdbased/BUILD                       |   1 +
 pkg/tcpip/link/fdbased/endpoint.go                 |   2 +-
 pkg/tcpip/link/sharedmem/BUILD                     |   2 +
 pkg/tcpip/link/sharedmem/pipe/BUILD                |   1 +
 pkg/tcpip/link/sharedmem/pipe/pipe_test.go         |   3 +-
 pkg/tcpip/link/sharedmem/sharedmem.go              |   2 +-
 pkg/tcpip/link/sharedmem/sharedmem_test.go         |   2 +-
 pkg/tcpip/network/fragmentation/BUILD              |   1 +
 pkg/tcpip/network/fragmentation/fragmentation.go   |   2 +-
 pkg/tcpip/network/fragmentation/reassembler.go     |   2 +-
 pkg/tcpip/ports/BUILD                              |   1 +
 pkg/tcpip/ports/ports.go                           |   2 +-
 pkg/tcpip/stack/BUILD                              |   2 +
 pkg/tcpip/stack/linkaddrcache.go                   |   2 +-
 pkg/tcpip/stack/linkaddrcache_test.go              |   2 +-
 pkg/tcpip/stack/nic.go                             |   2 +-
 pkg/tcpip/stack/stack.go                           |   2 +-
 pkg/tcpip/stack/transport_demuxer.go               |   2 +-
 pkg/tcpip/tcpip.go                                 |   2 +-
 pkg/tcpip/transport/icmp/BUILD                     |   1 +
 pkg/tcpip/transport/icmp/endpoint.go               |   3 +-
 pkg/tcpip/transport/packet/BUILD                   |   1 +
 pkg/tcpip/transport/packet/endpoint.go             |   3 +-
 pkg/tcpip/transport/raw/BUILD                      |   1 +
 pkg/tcpip/transport/raw/endpoint.go                |   3 +-
 pkg/tcpip/transport/tcp/BUILD                      |   1 +
 pkg/tcpip/transport/tcp/accept.go                  |   2 +-
 pkg/tcpip/transport/tcp/connect.go                 |   2 +-
 pkg/tcpip/transport/tcp/endpoint.go                |   2 +-
 pkg/tcpip/transport/tcp/endpoint_state.go          |   2 +-
 pkg/tcpip/transport/tcp/forwarder.go               |   3 +-
 pkg/tcpip/transport/tcp/protocol.go                |   2 +-
 pkg/tcpip/transport/tcp/segment_queue.go           |   2 +-
 pkg/tcpip/transport/tcp/snd.go                     |   2 +-
 pkg/tcpip/transport/udp/BUILD                      |   1 +
 pkg/tcpip/transport/udp/endpoint.go                |   3 +-
 pkg/tmutex/BUILD                                   |   1 +
 pkg/tmutex/tmutex_test.go                          |   3 +-
 pkg/unet/BUILD                                     |   1 +
 pkg/unet/unet_test.go                              |   3 +-
 pkg/urpc/BUILD                                     |   1 +
 pkg/urpc/urpc.go                                   |   2 +-
 pkg/waiter/BUILD                                   |   1 +
 pkg/waiter/waiter.go                               |   2 +-
 runsc/boot/BUILD                                   |   2 +
 runsc/boot/compat.go                               |   2 +-
 runsc/boot/limits.go                               |   2 +-
 runsc/boot/loader.go                               |   2 +-
 runsc/boot/loader_test.go                          |   2 +-
 runsc/cmd/BUILD                                    |   1 +
 runsc/cmd/create.go                                |   1 +
 runsc/cmd/gofer.go                                 |   2 +-
 runsc/cmd/start.go                                 |   1 +
 runsc/container/BUILD                              |   2 +
 runsc/container/console_test.go                    |   2 +-
 runsc/container/container_test.go                  |   2 +-
 runsc/container/multi_container_test.go            |   2 +-
 runsc/container/state_file.go                      |   2 +-
 runsc/fsgofer/BUILD                                |   1 +
 runsc/fsgofer/fsgofer.go                           |   2 +-
 runsc/sandbox/BUILD                                |   1 +
 runsc/sandbox/sandbox.go                           |   2 +-
 runsc/testutil/BUILD                               |   1 +
 runsc/testutil/testutil.go                         |   2 +-
 303 files changed, 1507 insertions(+), 1368 deletions(-)
 create mode 100644 pkg/sync/BUILD
 create mode 100644 pkg/sync/LICENSE
 create mode 100644 pkg/sync/README.md
 create mode 100644 pkg/sync/aliases.go
 create mode 100644 pkg/sync/atomicptr_unsafe.go
 create mode 100644 pkg/sync/atomicptrtest/BUILD
 create mode 100644 pkg/sync/atomicptrtest/atomicptr_test.go
 create mode 100644 pkg/sync/downgradable_rwmutex_test.go
 create mode 100644 pkg/sync/downgradable_rwmutex_unsafe.go
 create mode 100644 pkg/sync/memmove_unsafe.go
 create mode 100644 pkg/sync/norace_unsafe.go
 create mode 100644 pkg/sync/race_unsafe.go
 create mode 100644 pkg/sync/seqatomic_unsafe.go
 create mode 100644 pkg/sync/seqatomictest/BUILD
 create mode 100644 pkg/sync/seqatomictest/seqatomic_test.go
 create mode 100644 pkg/sync/seqcount.go
 create mode 100644 pkg/sync/seqcount_test.go
 create mode 100644 pkg/sync/syncutil.go
 delete mode 100644 pkg/syncutil/BUILD
 delete mode 100644 pkg/syncutil/LICENSE
 delete mode 100644 pkg/syncutil/README.md
 delete mode 100644 pkg/syncutil/atomicptr_unsafe.go
 delete mode 100644 pkg/syncutil/atomicptrtest/BUILD
 delete mode 100644 pkg/syncutil/atomicptrtest/atomicptr_test.go
 delete mode 100644 pkg/syncutil/downgradable_rwmutex_test.go
 delete mode 100644 pkg/syncutil/downgradable_rwmutex_unsafe.go
 delete mode 100644 pkg/syncutil/memmove_unsafe.go
 delete mode 100644 pkg/syncutil/norace_unsafe.go
 delete mode 100644 pkg/syncutil/race_unsafe.go
 delete mode 100644 pkg/syncutil/seqatomic_unsafe.go
 delete mode 100644 pkg/syncutil/seqatomictest/BUILD
 delete mode 100644 pkg/syncutil/seqatomictest/seqatomic_test.go
 delete mode 100644 pkg/syncutil/seqcount.go
 delete mode 100644 pkg/syncutil/seqcount_test.go
 delete mode 100644 pkg/syncutil/syncutil.go

(limited to 'pkg/tcpip/transport/tcp')

diff --git a/pkg/amutex/BUILD b/pkg/amutex/BUILD
index 6bc486b62..d99e37b40 100644
--- a/pkg/amutex/BUILD
+++ b/pkg/amutex/BUILD
@@ -15,4 +15,5 @@ go_test(
     size = "small",
     srcs = ["amutex_test.go"],
     embed = [":amutex"],
+    deps = ["//pkg/sync"],
 )
diff --git a/pkg/amutex/amutex_test.go b/pkg/amutex/amutex_test.go
index 1d7f45641..8a3952f2a 100644
--- a/pkg/amutex/amutex_test.go
+++ b/pkg/amutex/amutex_test.go
@@ -15,9 +15,10 @@
 package amutex
 
 import (
-	"sync"
 	"testing"
 	"time"
+
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 type sleeper struct {
diff --git a/pkg/atomicbitops/BUILD b/pkg/atomicbitops/BUILD
index 36beaade9..6403c60c2 100644
--- a/pkg/atomicbitops/BUILD
+++ b/pkg/atomicbitops/BUILD
@@ -20,4 +20,5 @@ go_test(
     size = "small",
     srcs = ["atomic_bitops_test.go"],
     embed = [":atomicbitops"],
+    deps = ["//pkg/sync"],
 )
diff --git a/pkg/atomicbitops/atomic_bitops_test.go b/pkg/atomicbitops/atomic_bitops_test.go
index 965e9be79..9466d3e23 100644
--- a/pkg/atomicbitops/atomic_bitops_test.go
+++ b/pkg/atomicbitops/atomic_bitops_test.go
@@ -16,8 +16,9 @@ package atomicbitops
 
 import (
 	"runtime"
-	"sync"
 	"testing"
+
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 const iterations = 100
diff --git a/pkg/compressio/BUILD b/pkg/compressio/BUILD
index a0b21d4bd..2bb581b18 100644
--- a/pkg/compressio/BUILD
+++ b/pkg/compressio/BUILD
@@ -8,7 +8,10 @@ go_library(
     srcs = ["compressio.go"],
     importpath = "gvisor.dev/gvisor/pkg/compressio",
     visibility = ["//:sandbox"],
-    deps = ["//pkg/binary"],
+    deps = [
+        "//pkg/binary",
+        "//pkg/sync",
+    ],
 )
 
 go_test(
diff --git a/pkg/compressio/compressio.go b/pkg/compressio/compressio.go
index 3b0bb086e..5f52cbe74 100644
--- a/pkg/compressio/compressio.go
+++ b/pkg/compressio/compressio.go
@@ -52,9 +52,9 @@ import (
 	"hash"
 	"io"
 	"runtime"
-	"sync"
 
 	"gvisor.dev/gvisor/pkg/binary"
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 var bufPool = sync.Pool{
diff --git a/pkg/control/server/BUILD b/pkg/control/server/BUILD
index 21adf3adf..adbd1e3f8 100644
--- a/pkg/control/server/BUILD
+++ b/pkg/control/server/BUILD
@@ -9,6 +9,7 @@ go_library(
     visibility = ["//:sandbox"],
     deps = [
         "//pkg/log",
+        "//pkg/sync",
         "//pkg/unet",
         "//pkg/urpc",
     ],
diff --git a/pkg/control/server/server.go b/pkg/control/server/server.go
index a56152d10..41abe1f2d 100644
--- a/pkg/control/server/server.go
+++ b/pkg/control/server/server.go
@@ -22,9 +22,9 @@ package server
 
 import (
 	"os"
-	"sync"
 
 	"gvisor.dev/gvisor/pkg/log"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/unet"
 	"gvisor.dev/gvisor/pkg/urpc"
 )
diff --git a/pkg/eventchannel/BUILD b/pkg/eventchannel/BUILD
index 0b4b7cc44..9d68682c7 100644
--- a/pkg/eventchannel/BUILD
+++ b/pkg/eventchannel/BUILD
@@ -15,6 +15,7 @@ go_library(
     deps = [
         ":eventchannel_go_proto",
         "//pkg/log",
+        "//pkg/sync",
         "//pkg/unet",
         "@com_github_golang_protobuf//proto:go_default_library",
         "@com_github_golang_protobuf//ptypes:go_default_library_gen",
@@ -40,6 +41,7 @@ go_test(
     srcs = ["event_test.go"],
     embed = [":eventchannel"],
     deps = [
+        "//pkg/sync",
         "@com_github_golang_protobuf//proto:go_default_library",
     ],
 )
diff --git a/pkg/eventchannel/event.go b/pkg/eventchannel/event.go
index d37ad0428..9a29c58bd 100644
--- a/pkg/eventchannel/event.go
+++ b/pkg/eventchannel/event.go
@@ -22,13 +22,13 @@ package eventchannel
 import (
 	"encoding/binary"
 	"fmt"
-	"sync"
 	"syscall"
 
 	"github.com/golang/protobuf/proto"
 	"github.com/golang/protobuf/ptypes"
 	pb "gvisor.dev/gvisor/pkg/eventchannel/eventchannel_go_proto"
 	"gvisor.dev/gvisor/pkg/log"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/unet"
 )
 
diff --git a/pkg/eventchannel/event_test.go b/pkg/eventchannel/event_test.go
index 3649097d6..7f41b4a27 100644
--- a/pkg/eventchannel/event_test.go
+++ b/pkg/eventchannel/event_test.go
@@ -16,11 +16,11 @@ package eventchannel
 
 import (
 	"fmt"
-	"sync"
 	"testing"
 	"time"
 
 	"github.com/golang/protobuf/proto"
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 // testEmitter is an emitter that can be used in tests. It records all events
diff --git a/pkg/fdchannel/BUILD b/pkg/fdchannel/BUILD
index 56495cbd9..b0478c672 100644
--- a/pkg/fdchannel/BUILD
+++ b/pkg/fdchannel/BUILD
@@ -15,4 +15,5 @@ go_test(
     size = "small",
     srcs = ["fdchannel_test.go"],
     embed = [":fdchannel"],
+    deps = ["//pkg/sync"],
 )
diff --git a/pkg/fdchannel/fdchannel_test.go b/pkg/fdchannel/fdchannel_test.go
index 5d01dc636..7a8a63a59 100644
--- a/pkg/fdchannel/fdchannel_test.go
+++ b/pkg/fdchannel/fdchannel_test.go
@@ -17,10 +17,11 @@ package fdchannel
 import (
 	"io/ioutil"
 	"os"
-	"sync"
 	"syscall"
 	"testing"
 	"time"
+
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 func TestSendRecvFD(t *testing.T) {
diff --git a/pkg/fdnotifier/BUILD b/pkg/fdnotifier/BUILD
index aca2d8a82..91a202a30 100644
--- a/pkg/fdnotifier/BUILD
+++ b/pkg/fdnotifier/BUILD
@@ -11,6 +11,7 @@ go_library(
     importpath = "gvisor.dev/gvisor/pkg/fdnotifier",
     visibility = ["//:sandbox"],
     deps = [
+        "//pkg/sync",
         "//pkg/waiter",
         "@org_golang_x_sys//unix:go_default_library",
     ],
diff --git a/pkg/fdnotifier/fdnotifier.go b/pkg/fdnotifier/fdnotifier.go
index f4aae1953..a6b63c982 100644
--- a/pkg/fdnotifier/fdnotifier.go
+++ b/pkg/fdnotifier/fdnotifier.go
@@ -22,10 +22,10 @@ package fdnotifier
 
 import (
 	"fmt"
-	"sync"
 	"syscall"
 
 	"golang.org/x/sys/unix"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/waiter"
 )
 
diff --git a/pkg/flipcall/BUILD b/pkg/flipcall/BUILD
index e590a71ba..85bd83af1 100644
--- a/pkg/flipcall/BUILD
+++ b/pkg/flipcall/BUILD
@@ -19,7 +19,7 @@ go_library(
         "//pkg/abi/linux",
         "//pkg/log",
         "//pkg/memutil",
-        "//pkg/syncutil",
+        "//pkg/sync",
     ],
 )
 
@@ -31,4 +31,5 @@ go_test(
         "flipcall_test.go",
     ],
     embed = [":flipcall"],
+    deps = ["//pkg/sync"],
 )
diff --git a/pkg/flipcall/flipcall_example_test.go b/pkg/flipcall/flipcall_example_test.go
index 8d88b845d..2e28a149a 100644
--- a/pkg/flipcall/flipcall_example_test.go
+++ b/pkg/flipcall/flipcall_example_test.go
@@ -17,7 +17,8 @@ package flipcall
 import (
 	"bytes"
 	"fmt"
-	"sync"
+
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 func Example() {
diff --git a/pkg/flipcall/flipcall_test.go b/pkg/flipcall/flipcall_test.go
index 168a487ec..33fd55a44 100644
--- a/pkg/flipcall/flipcall_test.go
+++ b/pkg/flipcall/flipcall_test.go
@@ -16,9 +16,10 @@ package flipcall
 
 import (
 	"runtime"
-	"sync"
 	"testing"
 	"time"
+
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 var testPacketWindowSize = pageSize
diff --git a/pkg/flipcall/flipcall_unsafe.go b/pkg/flipcall/flipcall_unsafe.go
index 27b8939fc..ac974b232 100644
--- a/pkg/flipcall/flipcall_unsafe.go
+++ b/pkg/flipcall/flipcall_unsafe.go
@@ -18,7 +18,7 @@ import (
 	"reflect"
 	"unsafe"
 
-	"gvisor.dev/gvisor/pkg/syncutil"
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 // Packets consist of a 16-byte header followed by an arbitrarily-sized
@@ -75,13 +75,13 @@ func (ep *Endpoint) Data() []byte {
 var ioSync int64
 
 func raceBecomeActive() {
-	if syncutil.RaceEnabled {
-		syncutil.RaceAcquire((unsafe.Pointer)(&ioSync))
+	if sync.RaceEnabled {
+		sync.RaceAcquire((unsafe.Pointer)(&ioSync))
 	}
 }
 
 func raceBecomeInactive() {
-	if syncutil.RaceEnabled {
-		syncutil.RaceReleaseMerge((unsafe.Pointer)(&ioSync))
+	if sync.RaceEnabled {
+		sync.RaceReleaseMerge((unsafe.Pointer)(&ioSync))
 	}
 }
diff --git a/pkg/gate/BUILD b/pkg/gate/BUILD
index 4b9321711..f22bd070d 100644
--- a/pkg/gate/BUILD
+++ b/pkg/gate/BUILD
@@ -19,5 +19,6 @@ go_test(
     ],
     deps = [
         ":gate",
+        "//pkg/sync",
     ],
 )
diff --git a/pkg/gate/gate_test.go b/pkg/gate/gate_test.go
index 5dbd8d712..850693df8 100644
--- a/pkg/gate/gate_test.go
+++ b/pkg/gate/gate_test.go
@@ -15,11 +15,11 @@
 package gate_test
 
 import (
-	"sync"
 	"testing"
 	"time"
 
 	"gvisor.dev/gvisor/pkg/gate"
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 func TestBasicEnter(t *testing.T) {
diff --git a/pkg/linewriter/BUILD b/pkg/linewriter/BUILD
index a5d980d14..bcde6d308 100644
--- a/pkg/linewriter/BUILD
+++ b/pkg/linewriter/BUILD
@@ -8,6 +8,7 @@ go_library(
     srcs = ["linewriter.go"],
     importpath = "gvisor.dev/gvisor/pkg/linewriter",
     visibility = ["//visibility:public"],
+    deps = ["//pkg/sync"],
 )
 
 go_test(
diff --git a/pkg/linewriter/linewriter.go b/pkg/linewriter/linewriter.go
index cd6e4e2ce..a1b1285d4 100644
--- a/pkg/linewriter/linewriter.go
+++ b/pkg/linewriter/linewriter.go
@@ -17,7 +17,8 @@ package linewriter
 
 import (
 	"bytes"
-	"sync"
+
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 // Writer is an io.Writer which buffers input, flushing
diff --git a/pkg/log/BUILD b/pkg/log/BUILD
index fc5f5779b..0df0f2849 100644
--- a/pkg/log/BUILD
+++ b/pkg/log/BUILD
@@ -16,7 +16,10 @@ go_library(
     visibility = [
         "//visibility:public",
     ],
-    deps = ["//pkg/linewriter"],
+    deps = [
+        "//pkg/linewriter",
+        "//pkg/sync",
+    ],
 )
 
 go_test(
diff --git a/pkg/log/log.go b/pkg/log/log.go
index 9387586e6..91a81b288 100644
--- a/pkg/log/log.go
+++ b/pkg/log/log.go
@@ -25,12 +25,12 @@ import (
 	stdlog "log"
 	"os"
 	"runtime"
-	"sync"
 	"sync/atomic"
 	"syscall"
 	"time"
 
 	"gvisor.dev/gvisor/pkg/linewriter"
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 // Level is the log level.
diff --git a/pkg/metric/BUILD b/pkg/metric/BUILD
index dd6ca6d39..9145f3233 100644
--- a/pkg/metric/BUILD
+++ b/pkg/metric/BUILD
@@ -14,6 +14,7 @@ go_library(
         ":metric_go_proto",
         "//pkg/eventchannel",
         "//pkg/log",
+        "//pkg/sync",
     ],
 )
 
diff --git a/pkg/metric/metric.go b/pkg/metric/metric.go
index eadde06e4..93d4f2b8c 100644
--- a/pkg/metric/metric.go
+++ b/pkg/metric/metric.go
@@ -18,12 +18,12 @@ package metric
 import (
 	"errors"
 	"fmt"
-	"sync"
 	"sync/atomic"
 
 	"gvisor.dev/gvisor/pkg/eventchannel"
 	"gvisor.dev/gvisor/pkg/log"
 	pb "gvisor.dev/gvisor/pkg/metric/metric_go_proto"
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 var (
diff --git a/pkg/p9/BUILD b/pkg/p9/BUILD
index f32244c69..a3e05c96d 100644
--- a/pkg/p9/BUILD
+++ b/pkg/p9/BUILD
@@ -29,6 +29,7 @@ go_library(
         "//pkg/fdchannel",
         "//pkg/flipcall",
         "//pkg/log",
+        "//pkg/sync",
         "//pkg/unet",
         "@org_golang_x_sys//unix:go_default_library",
     ],
diff --git a/pkg/p9/client.go b/pkg/p9/client.go
index 221516c6c..4045e41fa 100644
--- a/pkg/p9/client.go
+++ b/pkg/p9/client.go
@@ -17,12 +17,12 @@ package p9
 import (
 	"errors"
 	"fmt"
-	"sync"
 	"syscall"
 
 	"golang.org/x/sys/unix"
 	"gvisor.dev/gvisor/pkg/flipcall"
 	"gvisor.dev/gvisor/pkg/log"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/unet"
 )
 
diff --git a/pkg/p9/p9test/BUILD b/pkg/p9/p9test/BUILD
index 28707c0ca..f4edd68b2 100644
--- a/pkg/p9/p9test/BUILD
+++ b/pkg/p9/p9test/BUILD
@@ -70,6 +70,7 @@ go_library(
         "//pkg/fd",
         "//pkg/log",
         "//pkg/p9",
+        "//pkg/sync",
         "//pkg/unet",
         "@com_github_golang_mock//gomock:go_default_library",
     ],
@@ -83,6 +84,7 @@ go_test(
     deps = [
         "//pkg/fd",
         "//pkg/p9",
+        "//pkg/sync",
         "@com_github_golang_mock//gomock:go_default_library",
     ],
 )
diff --git a/pkg/p9/p9test/client_test.go b/pkg/p9/p9test/client_test.go
index 6e758148d..6e7bb3db2 100644
--- a/pkg/p9/p9test/client_test.go
+++ b/pkg/p9/p9test/client_test.go
@@ -22,7 +22,6 @@ import (
 	"os"
 	"reflect"
 	"strings"
-	"sync"
 	"syscall"
 	"testing"
 	"time"
@@ -30,6 +29,7 @@ import (
 	"github.com/golang/mock/gomock"
 	"gvisor.dev/gvisor/pkg/fd"
 	"gvisor.dev/gvisor/pkg/p9"
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 func TestPanic(t *testing.T) {
diff --git a/pkg/p9/p9test/p9test.go b/pkg/p9/p9test/p9test.go
index 4d3271b37..dd8b01b6d 100644
--- a/pkg/p9/p9test/p9test.go
+++ b/pkg/p9/p9test/p9test.go
@@ -17,13 +17,13 @@ package p9test
 
 import (
 	"fmt"
-	"sync"
 	"sync/atomic"
 	"syscall"
 	"testing"
 
 	"github.com/golang/mock/gomock"
 	"gvisor.dev/gvisor/pkg/p9"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/unet"
 )
 
diff --git a/pkg/p9/path_tree.go b/pkg/p9/path_tree.go
index 865459411..72ef53313 100644
--- a/pkg/p9/path_tree.go
+++ b/pkg/p9/path_tree.go
@@ -16,7 +16,8 @@ package p9
 
 import (
 	"fmt"
-	"sync"
+
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 // pathNode is a single node in a path traversal.
diff --git a/pkg/p9/pool.go b/pkg/p9/pool.go
index 52de889e1..2b14a5ce3 100644
--- a/pkg/p9/pool.go
+++ b/pkg/p9/pool.go
@@ -15,7 +15,7 @@
 package p9
 
 import (
-	"sync"
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 // pool is a simple allocator.
diff --git a/pkg/p9/server.go b/pkg/p9/server.go
index 40b8fa023..fdfa83648 100644
--- a/pkg/p9/server.go
+++ b/pkg/p9/server.go
@@ -17,7 +17,6 @@ package p9
 import (
 	"io"
 	"runtime/debug"
-	"sync"
 	"sync/atomic"
 	"syscall"
 
@@ -25,6 +24,7 @@ import (
 	"gvisor.dev/gvisor/pkg/fdchannel"
 	"gvisor.dev/gvisor/pkg/flipcall"
 	"gvisor.dev/gvisor/pkg/log"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/unet"
 )
 
diff --git a/pkg/p9/transport.go b/pkg/p9/transport.go
index 6e8b4bbcd..9c11e28ce 100644
--- a/pkg/p9/transport.go
+++ b/pkg/p9/transport.go
@@ -19,11 +19,11 @@ import (
 	"fmt"
 	"io"
 	"io/ioutil"
-	"sync"
 	"syscall"
 
 	"gvisor.dev/gvisor/pkg/fd"
 	"gvisor.dev/gvisor/pkg/log"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/unet"
 )
 
diff --git a/pkg/procid/BUILD b/pkg/procid/BUILD
index 078f084b2..b506813f0 100644
--- a/pkg/procid/BUILD
+++ b/pkg/procid/BUILD
@@ -21,6 +21,7 @@ go_test(
         "procid_test.go",
     ],
     embed = [":procid"],
+    deps = ["//pkg/sync"],
 )
 
 go_test(
@@ -31,4 +32,5 @@ go_test(
         "procid_test.go",
     ],
     embed = [":procid"],
+    deps = ["//pkg/sync"],
 )
diff --git a/pkg/procid/procid_test.go b/pkg/procid/procid_test.go
index 88dd0b3ae..9ec08c3d6 100644
--- a/pkg/procid/procid_test.go
+++ b/pkg/procid/procid_test.go
@@ -17,9 +17,10 @@ package procid
 import (
 	"os"
 	"runtime"
-	"sync"
 	"syscall"
 	"testing"
+
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 // runOnMain is used to send functions to run on the main (initial) thread.
diff --git a/pkg/rand/BUILD b/pkg/rand/BUILD
index f4f2001f3..9d5b4859b 100644
--- a/pkg/rand/BUILD
+++ b/pkg/rand/BUILD
@@ -10,5 +10,8 @@ go_library(
     ],
     importpath = "gvisor.dev/gvisor/pkg/rand",
     visibility = ["//:sandbox"],
-    deps = ["@org_golang_x_sys//unix:go_default_library"],
+    deps = [
+        "//pkg/sync",
+        "@org_golang_x_sys//unix:go_default_library",
+    ],
 )
diff --git a/pkg/rand/rand_linux.go b/pkg/rand/rand_linux.go
index 2b92db3e6..0bdad5fad 100644
--- a/pkg/rand/rand_linux.go
+++ b/pkg/rand/rand_linux.go
@@ -19,9 +19,9 @@ package rand
 import (
 	"crypto/rand"
 	"io"
-	"sync"
 
 	"golang.org/x/sys/unix"
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 // reader implements an io.Reader that returns pseudorandom bytes.
diff --git a/pkg/refs/BUILD b/pkg/refs/BUILD
index 7ad59dfd7..974d9af9b 100644
--- a/pkg/refs/BUILD
+++ b/pkg/refs/BUILD
@@ -27,6 +27,7 @@ go_library(
     visibility = ["//:sandbox"],
     deps = [
         "//pkg/log",
+        "//pkg/sync",
     ],
 )
 
@@ -35,4 +36,5 @@ go_test(
     size = "small",
     srcs = ["refcounter_test.go"],
     embed = [":refs"],
+    deps = ["//pkg/sync"],
 )
diff --git a/pkg/refs/refcounter.go b/pkg/refs/refcounter.go
index ad69e0757..c45ba8200 100644
--- a/pkg/refs/refcounter.go
+++ b/pkg/refs/refcounter.go
@@ -21,10 +21,10 @@ import (
 	"fmt"
 	"reflect"
 	"runtime"
-	"sync"
 	"sync/atomic"
 
 	"gvisor.dev/gvisor/pkg/log"
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 // RefCounter is the interface to be implemented by objects that are reference
diff --git a/pkg/refs/refcounter_test.go b/pkg/refs/refcounter_test.go
index ffd3d3f07..1ab4a4440 100644
--- a/pkg/refs/refcounter_test.go
+++ b/pkg/refs/refcounter_test.go
@@ -16,8 +16,9 @@ package refs
 
 import (
 	"reflect"
-	"sync"
 	"testing"
+
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 type testCounter struct {
diff --git a/pkg/sentry/arch/BUILD b/pkg/sentry/arch/BUILD
index 18c73cc24..ae3e364cd 100644
--- a/pkg/sentry/arch/BUILD
+++ b/pkg/sentry/arch/BUILD
@@ -32,6 +32,7 @@ go_library(
         "//pkg/sentry/context",
         "//pkg/sentry/limits",
         "//pkg/sentry/usermem",
+        "//pkg/sync",
         "//pkg/syserror",
     ],
 )
diff --git a/pkg/sentry/arch/arch_x86.go b/pkg/sentry/arch/arch_x86.go
index 9294ac773..9f41e566f 100644
--- a/pkg/sentry/arch/arch_x86.go
+++ b/pkg/sentry/arch/arch_x86.go
@@ -19,7 +19,6 @@ package arch
 import (
 	"fmt"
 	"io"
-	"sync"
 	"syscall"
 
 	"gvisor.dev/gvisor/pkg/binary"
@@ -27,6 +26,7 @@ import (
 	"gvisor.dev/gvisor/pkg/log"
 	rpb "gvisor.dev/gvisor/pkg/sentry/arch/registers_go_proto"
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/syserror"
 )
 
diff --git a/pkg/sentry/control/BUILD b/pkg/sentry/control/BUILD
index 5522cecd0..2561a6109 100644
--- a/pkg/sentry/control/BUILD
+++ b/pkg/sentry/control/BUILD
@@ -30,6 +30,7 @@ go_library(
         "//pkg/sentry/strace",
         "//pkg/sentry/usage",
         "//pkg/sentry/watchdog",
+        "//pkg/sync",
         "//pkg/tcpip/link/sniffer",
         "//pkg/urpc",
     ],
diff --git a/pkg/sentry/control/pprof.go b/pkg/sentry/control/pprof.go
index e1f2fea60..151808911 100644
--- a/pkg/sentry/control/pprof.go
+++ b/pkg/sentry/control/pprof.go
@@ -19,10 +19,10 @@ import (
 	"runtime"
 	"runtime/pprof"
 	"runtime/trace"
-	"sync"
 
 	"gvisor.dev/gvisor/pkg/fd"
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/urpc"
 )
 
diff --git a/pkg/sentry/device/BUILD b/pkg/sentry/device/BUILD
index 1098ed777..97fa1512c 100644
--- a/pkg/sentry/device/BUILD
+++ b/pkg/sentry/device/BUILD
@@ -8,7 +8,10 @@ go_library(
     srcs = ["device.go"],
     importpath = "gvisor.dev/gvisor/pkg/sentry/device",
     visibility = ["//pkg/sentry:internal"],
-    deps = ["//pkg/abi/linux"],
+    deps = [
+        "//pkg/abi/linux",
+        "//pkg/sync",
+    ],
 )
 
 go_test(
diff --git a/pkg/sentry/device/device.go b/pkg/sentry/device/device.go
index 47945d1a7..69e71e322 100644
--- a/pkg/sentry/device/device.go
+++ b/pkg/sentry/device/device.go
@@ -19,10 +19,10 @@ package device
 import (
 	"bytes"
 	"fmt"
-	"sync"
 	"sync/atomic"
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 // Registry tracks all simple devices and related state on the system for
diff --git a/pkg/sentry/fs/BUILD b/pkg/sentry/fs/BUILD
index c035ffff7..7d5d72d5a 100644
--- a/pkg/sentry/fs/BUILD
+++ b/pkg/sentry/fs/BUILD
@@ -68,7 +68,7 @@ go_library(
         "//pkg/sentry/usage",
         "//pkg/sentry/usermem",
         "//pkg/state",
-        "//pkg/syncutil",
+        "//pkg/sync",
         "//pkg/syserror",
         "//pkg/waiter",
     ],
@@ -115,6 +115,7 @@ go_test(
         "//pkg/sentry/fs/tmpfs",
         "//pkg/sentry/kernel/contexttest",
         "//pkg/sentry/usermem",
+        "//pkg/sync",
         "//pkg/syserror",
     ],
 )
diff --git a/pkg/sentry/fs/copy_up.go b/pkg/sentry/fs/copy_up.go
index 9ac62c84d..734177e90 100644
--- a/pkg/sentry/fs/copy_up.go
+++ b/pkg/sentry/fs/copy_up.go
@@ -17,12 +17,12 @@ package fs
 import (
 	"fmt"
 	"io"
-	"sync"
 
 	"gvisor.dev/gvisor/pkg/log"
 	"gvisor.dev/gvisor/pkg/sentry/context"
 	"gvisor.dev/gvisor/pkg/sentry/memmap"
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/syserror"
 )
 
diff --git a/pkg/sentry/fs/copy_up_test.go b/pkg/sentry/fs/copy_up_test.go
index 1d80bf15a..738580c5f 100644
--- a/pkg/sentry/fs/copy_up_test.go
+++ b/pkg/sentry/fs/copy_up_test.go
@@ -19,13 +19,13 @@ import (
 	"crypto/rand"
 	"fmt"
 	"io"
-	"sync"
 	"testing"
 
 	"gvisor.dev/gvisor/pkg/sentry/fs"
 	_ "gvisor.dev/gvisor/pkg/sentry/fs/tmpfs"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/contexttest"
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 const (
diff --git a/pkg/sentry/fs/dirent.go b/pkg/sentry/fs/dirent.go
index 3cb73bd78..31fc4d87b 100644
--- a/pkg/sentry/fs/dirent.go
+++ b/pkg/sentry/fs/dirent.go
@@ -18,7 +18,6 @@ import (
 	"fmt"
 	"path"
 	"sort"
-	"sync"
 	"sync/atomic"
 	"syscall"
 
@@ -28,6 +27,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
 	"gvisor.dev/gvisor/pkg/sentry/socket/unix/transport"
 	"gvisor.dev/gvisor/pkg/sentry/uniqueid"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/syserror"
 )
 
diff --git a/pkg/sentry/fs/dirent_cache.go b/pkg/sentry/fs/dirent_cache.go
index 60a15a275..25514ace4 100644
--- a/pkg/sentry/fs/dirent_cache.go
+++ b/pkg/sentry/fs/dirent_cache.go
@@ -16,7 +16,8 @@ package fs
 
 import (
 	"fmt"
-	"sync"
+
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 // DirentCache is an LRU cache of Dirents. The Dirent's refCount is
diff --git a/pkg/sentry/fs/dirent_cache_limiter.go b/pkg/sentry/fs/dirent_cache_limiter.go
index ebb80bd50..525ee25f9 100644
--- a/pkg/sentry/fs/dirent_cache_limiter.go
+++ b/pkg/sentry/fs/dirent_cache_limiter.go
@@ -16,7 +16,8 @@ package fs
 
 import (
 	"fmt"
-	"sync"
+
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 // DirentCacheLimiter acts as a global limit for all dirent caches in the
diff --git a/pkg/sentry/fs/fdpipe/BUILD b/pkg/sentry/fs/fdpipe/BUILD
index 277ee4c31..cc43de69d 100644
--- a/pkg/sentry/fs/fdpipe/BUILD
+++ b/pkg/sentry/fs/fdpipe/BUILD
@@ -23,6 +23,7 @@ go_library(
         "//pkg/sentry/fs/fsutil",
         "//pkg/sentry/safemem",
         "//pkg/sentry/usermem",
+        "//pkg/sync",
         "//pkg/syserror",
         "//pkg/waiter",
     ],
diff --git a/pkg/sentry/fs/fdpipe/pipe.go b/pkg/sentry/fs/fdpipe/pipe.go
index 669ffcb75..5b6cfeb0a 100644
--- a/pkg/sentry/fs/fdpipe/pipe.go
+++ b/pkg/sentry/fs/fdpipe/pipe.go
@@ -17,7 +17,6 @@ package fdpipe
 
 import (
 	"os"
-	"sync"
 	"syscall"
 
 	"gvisor.dev/gvisor/pkg/fd"
@@ -29,6 +28,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/fs/fsutil"
 	"gvisor.dev/gvisor/pkg/sentry/safemem"
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/syserror"
 	"gvisor.dev/gvisor/pkg/waiter"
 )
diff --git a/pkg/sentry/fs/fdpipe/pipe_state.go b/pkg/sentry/fs/fdpipe/pipe_state.go
index 29175fb3d..cee87f726 100644
--- a/pkg/sentry/fs/fdpipe/pipe_state.go
+++ b/pkg/sentry/fs/fdpipe/pipe_state.go
@@ -17,10 +17,10 @@ package fdpipe
 import (
 	"fmt"
 	"io/ioutil"
-	"sync"
 
 	"gvisor.dev/gvisor/pkg/sentry/context"
 	"gvisor.dev/gvisor/pkg/sentry/fs"
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 // beforeSave is invoked by stateify.
diff --git a/pkg/sentry/fs/file.go b/pkg/sentry/fs/file.go
index a2f966cb6..7c4586296 100644
--- a/pkg/sentry/fs/file.go
+++ b/pkg/sentry/fs/file.go
@@ -16,7 +16,6 @@ package fs
 
 import (
 	"math"
-	"sync"
 	"sync/atomic"
 	"time"
 
@@ -29,6 +28,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/memmap"
 	"gvisor.dev/gvisor/pkg/sentry/uniqueid"
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/syserror"
 	"gvisor.dev/gvisor/pkg/waiter"
 )
diff --git a/pkg/sentry/fs/file_overlay.go b/pkg/sentry/fs/file_overlay.go
index 225e40186..8a633b1ba 100644
--- a/pkg/sentry/fs/file_overlay.go
+++ b/pkg/sentry/fs/file_overlay.go
@@ -16,13 +16,13 @@ package fs
 
 import (
 	"io"
-	"sync"
 
 	"gvisor.dev/gvisor/pkg/refs"
 	"gvisor.dev/gvisor/pkg/sentry/arch"
 	"gvisor.dev/gvisor/pkg/sentry/context"
 	"gvisor.dev/gvisor/pkg/sentry/memmap"
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/syserror"
 	"gvisor.dev/gvisor/pkg/waiter"
 )
diff --git a/pkg/sentry/fs/filesystems.go b/pkg/sentry/fs/filesystems.go
index b157fd228..c5b51620a 100644
--- a/pkg/sentry/fs/filesystems.go
+++ b/pkg/sentry/fs/filesystems.go
@@ -18,9 +18,9 @@ import (
 	"fmt"
 	"sort"
 	"strings"
-	"sync"
 
 	"gvisor.dev/gvisor/pkg/sentry/context"
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 // FilesystemFlags matches include/linux/fs.h:file_system_type.fs_flags.
diff --git a/pkg/sentry/fs/fs.go b/pkg/sentry/fs/fs.go
index 8b2a5e6b2..26abf49e2 100644
--- a/pkg/sentry/fs/fs.go
+++ b/pkg/sentry/fs/fs.go
@@ -54,10 +54,9 @@
 package fs
 
 import (
-	"sync"
-
 	"gvisor.dev/gvisor/pkg/log"
 	"gvisor.dev/gvisor/pkg/sentry/context"
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 var (
diff --git a/pkg/sentry/fs/fsutil/BUILD b/pkg/sentry/fs/fsutil/BUILD
index 9ca695a95..945b6270d 100644
--- a/pkg/sentry/fs/fsutil/BUILD
+++ b/pkg/sentry/fs/fsutil/BUILD
@@ -93,6 +93,7 @@ go_library(
         "//pkg/sentry/usage",
         "//pkg/sentry/usermem",
         "//pkg/state",
+        "//pkg/sync",
         "//pkg/syserror",
         "//pkg/waiter",
     ],
diff --git a/pkg/sentry/fs/fsutil/host_file_mapper.go b/pkg/sentry/fs/fsutil/host_file_mapper.go
index b06a71cc2..837fc70b5 100644
--- a/pkg/sentry/fs/fsutil/host_file_mapper.go
+++ b/pkg/sentry/fs/fsutil/host_file_mapper.go
@@ -16,7 +16,6 @@ package fsutil
 
 import (
 	"fmt"
-	"sync"
 	"syscall"
 
 	"gvisor.dev/gvisor/pkg/log"
@@ -24,6 +23,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/platform"
 	"gvisor.dev/gvisor/pkg/sentry/safemem"
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 // HostFileMapper caches mappings of an arbitrary host file descriptor. It is
diff --git a/pkg/sentry/fs/fsutil/host_mappable.go b/pkg/sentry/fs/fsutil/host_mappable.go
index 30475f340..a625f0e26 100644
--- a/pkg/sentry/fs/fsutil/host_mappable.go
+++ b/pkg/sentry/fs/fsutil/host_mappable.go
@@ -16,7 +16,6 @@ package fsutil
 
 import (
 	"math"
-	"sync"
 
 	"gvisor.dev/gvisor/pkg/sentry/context"
 	"gvisor.dev/gvisor/pkg/sentry/fs"
@@ -24,6 +23,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/platform"
 	"gvisor.dev/gvisor/pkg/sentry/safemem"
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 // HostMappable implements memmap.Mappable and platform.File over a
diff --git a/pkg/sentry/fs/fsutil/inode.go b/pkg/sentry/fs/fsutil/inode.go
index 4e100a402..adf5ec69c 100644
--- a/pkg/sentry/fs/fsutil/inode.go
+++ b/pkg/sentry/fs/fsutil/inode.go
@@ -15,13 +15,12 @@
 package fsutil
 
 import (
-	"sync"
-
 	"gvisor.dev/gvisor/pkg/sentry/context"
 	"gvisor.dev/gvisor/pkg/sentry/fs"
 	ktime "gvisor.dev/gvisor/pkg/sentry/kernel/time"
 	"gvisor.dev/gvisor/pkg/sentry/memmap"
 	"gvisor.dev/gvisor/pkg/sentry/socket/unix/transport"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/syserror"
 	"gvisor.dev/gvisor/pkg/waiter"
 )
diff --git a/pkg/sentry/fs/fsutil/inode_cached.go b/pkg/sentry/fs/fsutil/inode_cached.go
index 798920d18..20a014402 100644
--- a/pkg/sentry/fs/fsutil/inode_cached.go
+++ b/pkg/sentry/fs/fsutil/inode_cached.go
@@ -17,7 +17,6 @@ package fsutil
 import (
 	"fmt"
 	"io"
-	"sync"
 
 	"gvisor.dev/gvisor/pkg/log"
 	"gvisor.dev/gvisor/pkg/sentry/context"
@@ -30,6 +29,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/safemem"
 	"gvisor.dev/gvisor/pkg/sentry/usage"
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 // Lock order (compare the lock order model in mm/mm.go):
diff --git a/pkg/sentry/fs/gofer/BUILD b/pkg/sentry/fs/gofer/BUILD
index 4a005c605..fd870e8e1 100644
--- a/pkg/sentry/fs/gofer/BUILD
+++ b/pkg/sentry/fs/gofer/BUILD
@@ -44,6 +44,7 @@ go_library(
         "//pkg/sentry/safemem",
         "//pkg/sentry/socket/unix/transport",
         "//pkg/sentry/usermem",
+        "//pkg/sync",
         "//pkg/syserr",
         "//pkg/syserror",
         "//pkg/unet",
diff --git a/pkg/sentry/fs/gofer/inode.go b/pkg/sentry/fs/gofer/inode.go
index 91263ebdc..245fe2ef1 100644
--- a/pkg/sentry/fs/gofer/inode.go
+++ b/pkg/sentry/fs/gofer/inode.go
@@ -16,7 +16,6 @@ package gofer
 
 import (
 	"errors"
-	"sync"
 	"syscall"
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
@@ -31,6 +30,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/fs/host"
 	"gvisor.dev/gvisor/pkg/sentry/memmap"
 	"gvisor.dev/gvisor/pkg/sentry/safemem"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/syserror"
 )
 
diff --git a/pkg/sentry/fs/gofer/session.go b/pkg/sentry/fs/gofer/session.go
index 4e358a46a..edc796ce0 100644
--- a/pkg/sentry/fs/gofer/session.go
+++ b/pkg/sentry/fs/gofer/session.go
@@ -16,7 +16,6 @@ package gofer
 
 import (
 	"fmt"
-	"sync"
 
 	"gvisor.dev/gvisor/pkg/p9"
 	"gvisor.dev/gvisor/pkg/refs"
@@ -25,6 +24,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/fs"
 	"gvisor.dev/gvisor/pkg/sentry/fs/fsutil"
 	"gvisor.dev/gvisor/pkg/sentry/socket/unix/transport"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/unet"
 )
 
diff --git a/pkg/sentry/fs/host/BUILD b/pkg/sentry/fs/host/BUILD
index 23daeb528..2b581aa69 100644
--- a/pkg/sentry/fs/host/BUILD
+++ b/pkg/sentry/fs/host/BUILD
@@ -50,6 +50,7 @@ go_library(
         "//pkg/sentry/unimpl",
         "//pkg/sentry/uniqueid",
         "//pkg/sentry/usermem",
+        "//pkg/sync",
         "//pkg/syserr",
         "//pkg/syserror",
         "//pkg/tcpip",
diff --git a/pkg/sentry/fs/host/inode.go b/pkg/sentry/fs/host/inode.go
index a6e4a09e3..873a1c52d 100644
--- a/pkg/sentry/fs/host/inode.go
+++ b/pkg/sentry/fs/host/inode.go
@@ -15,7 +15,6 @@
 package host
 
 import (
-	"sync"
 	"syscall"
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
@@ -28,6 +27,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/memmap"
 	"gvisor.dev/gvisor/pkg/sentry/safemem"
 	"gvisor.dev/gvisor/pkg/sentry/socket/unix/transport"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/syserror"
 	"gvisor.dev/gvisor/pkg/waiter"
 )
diff --git a/pkg/sentry/fs/host/socket.go b/pkg/sentry/fs/host/socket.go
index 107336a3e..c076d5bdd 100644
--- a/pkg/sentry/fs/host/socket.go
+++ b/pkg/sentry/fs/host/socket.go
@@ -16,7 +16,6 @@ package host
 
 import (
 	"fmt"
-	"sync"
 	"syscall"
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
@@ -30,6 +29,7 @@ import (
 	unixsocket "gvisor.dev/gvisor/pkg/sentry/socket/unix"
 	"gvisor.dev/gvisor/pkg/sentry/socket/unix/transport"
 	"gvisor.dev/gvisor/pkg/sentry/uniqueid"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/syserr"
 	"gvisor.dev/gvisor/pkg/syserror"
 	"gvisor.dev/gvisor/pkg/tcpip"
diff --git a/pkg/sentry/fs/host/tty.go b/pkg/sentry/fs/host/tty.go
index 90331e3b2..753ef8cd6 100644
--- a/pkg/sentry/fs/host/tty.go
+++ b/pkg/sentry/fs/host/tty.go
@@ -15,8 +15,6 @@
 package host
 
 import (
-	"sync"
-
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/sentry/arch"
 	"gvisor.dev/gvisor/pkg/sentry/context"
@@ -24,6 +22,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
 	"gvisor.dev/gvisor/pkg/sentry/unimpl"
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/syserror"
 )
 
diff --git a/pkg/sentry/fs/inode.go b/pkg/sentry/fs/inode.go
index 91e2fde2f..468043df0 100644
--- a/pkg/sentry/fs/inode.go
+++ b/pkg/sentry/fs/inode.go
@@ -15,8 +15,6 @@
 package fs
 
 import (
-	"sync"
-
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/log"
 	"gvisor.dev/gvisor/pkg/metric"
@@ -26,6 +24,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
 	"gvisor.dev/gvisor/pkg/sentry/memmap"
 	"gvisor.dev/gvisor/pkg/sentry/socket/unix/transport"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/syserror"
 )
 
diff --git a/pkg/sentry/fs/inode_inotify.go b/pkg/sentry/fs/inode_inotify.go
index 0f2a66a79..efd3c962b 100644
--- a/pkg/sentry/fs/inode_inotify.go
+++ b/pkg/sentry/fs/inode_inotify.go
@@ -16,7 +16,8 @@ package fs
 
 import (
 	"fmt"
-	"sync"
+
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 // Watches is the collection of inotify watches on an inode.
diff --git a/pkg/sentry/fs/inotify.go b/pkg/sentry/fs/inotify.go
index ba3e0233d..cc7dd1c92 100644
--- a/pkg/sentry/fs/inotify.go
+++ b/pkg/sentry/fs/inotify.go
@@ -16,7 +16,6 @@ package fs
 
 import (
 	"io"
-	"sync"
 	"sync/atomic"
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
@@ -25,6 +24,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/memmap"
 	"gvisor.dev/gvisor/pkg/sentry/uniqueid"
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/syserror"
 	"gvisor.dev/gvisor/pkg/waiter"
 )
diff --git a/pkg/sentry/fs/inotify_watch.go b/pkg/sentry/fs/inotify_watch.go
index 0aa0a5e9b..900cba3ca 100644
--- a/pkg/sentry/fs/inotify_watch.go
+++ b/pkg/sentry/fs/inotify_watch.go
@@ -15,10 +15,10 @@
 package fs
 
 import (
-	"sync"
 	"sync/atomic"
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 // Watch represent a particular inotify watch created by inotify_add_watch.
diff --git a/pkg/sentry/fs/lock/BUILD b/pkg/sentry/fs/lock/BUILD
index 8d62642e7..2c332a82a 100644
--- a/pkg/sentry/fs/lock/BUILD
+++ b/pkg/sentry/fs/lock/BUILD
@@ -44,6 +44,7 @@ go_library(
     visibility = ["//pkg/sentry:internal"],
     deps = [
         "//pkg/log",
+        "//pkg/sync",
         "//pkg/waiter",
     ],
 )
diff --git a/pkg/sentry/fs/lock/lock.go b/pkg/sentry/fs/lock/lock.go
index 636484424..41b040818 100644
--- a/pkg/sentry/fs/lock/lock.go
+++ b/pkg/sentry/fs/lock/lock.go
@@ -52,9 +52,9 @@ package lock
 import (
 	"fmt"
 	"math"
-	"sync"
 	"syscall"
 
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/waiter"
 )
 
diff --git a/pkg/sentry/fs/mounts.go b/pkg/sentry/fs/mounts.go
index ac0398bd9..db3dfd096 100644
--- a/pkg/sentry/fs/mounts.go
+++ b/pkg/sentry/fs/mounts.go
@@ -19,7 +19,6 @@ import (
 	"math"
 	"path"
 	"strings"
-	"sync"
 	"syscall"
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
@@ -27,6 +26,7 @@ import (
 	"gvisor.dev/gvisor/pkg/refs"
 	"gvisor.dev/gvisor/pkg/sentry/context"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/syserror"
 )
 
diff --git a/pkg/sentry/fs/overlay.go b/pkg/sentry/fs/overlay.go
index 25573e986..4cad55327 100644
--- a/pkg/sentry/fs/overlay.go
+++ b/pkg/sentry/fs/overlay.go
@@ -17,13 +17,12 @@ package fs
 import (
 	"fmt"
 	"strings"
-	"sync"
 
 	"gvisor.dev/gvisor/pkg/log"
 	"gvisor.dev/gvisor/pkg/sentry/context"
 	"gvisor.dev/gvisor/pkg/sentry/memmap"
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
-	"gvisor.dev/gvisor/pkg/syncutil"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/syserror"
 )
 
@@ -199,7 +198,7 @@ type overlayEntry struct {
 	upper *Inode
 
 	// dirCacheMu protects dirCache.
-	dirCacheMu syncutil.DowngradableRWMutex `state:"nosave"`
+	dirCacheMu sync.DowngradableRWMutex `state:"nosave"`
 
 	// dirCache is cache of DentAttrs from upper and lower Inodes.
 	dirCache *SortedDentryMap
diff --git a/pkg/sentry/fs/proc/BUILD b/pkg/sentry/fs/proc/BUILD
index 75cbb0622..94d46ab1b 100644
--- a/pkg/sentry/fs/proc/BUILD
+++ b/pkg/sentry/fs/proc/BUILD
@@ -51,6 +51,7 @@ go_library(
         "//pkg/sentry/socket/unix/transport",
         "//pkg/sentry/usage",
         "//pkg/sentry/usermem",
+        "//pkg/sync",
         "//pkg/syserror",
         "//pkg/tcpip/header",
         "//pkg/waiter",
diff --git a/pkg/sentry/fs/proc/seqfile/BUILD b/pkg/sentry/fs/proc/seqfile/BUILD
index fe7067be1..38b246dff 100644
--- a/pkg/sentry/fs/proc/seqfile/BUILD
+++ b/pkg/sentry/fs/proc/seqfile/BUILD
@@ -16,6 +16,7 @@ go_library(
         "//pkg/sentry/fs/proc/device",
         "//pkg/sentry/kernel/time",
         "//pkg/sentry/usermem",
+        "//pkg/sync",
         "//pkg/syserror",
         "//pkg/waiter",
     ],
diff --git a/pkg/sentry/fs/proc/seqfile/seqfile.go b/pkg/sentry/fs/proc/seqfile/seqfile.go
index 5fe823000..f9af191d5 100644
--- a/pkg/sentry/fs/proc/seqfile/seqfile.go
+++ b/pkg/sentry/fs/proc/seqfile/seqfile.go
@@ -17,7 +17,6 @@ package seqfile
 
 import (
 	"io"
-	"sync"
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/sentry/context"
@@ -26,6 +25,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/fs/proc/device"
 	ktime "gvisor.dev/gvisor/pkg/sentry/kernel/time"
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/syserror"
 	"gvisor.dev/gvisor/pkg/waiter"
 )
diff --git a/pkg/sentry/fs/proc/sys_net.go b/pkg/sentry/fs/proc/sys_net.go
index bd93f83fa..a37e1fa06 100644
--- a/pkg/sentry/fs/proc/sys_net.go
+++ b/pkg/sentry/fs/proc/sys_net.go
@@ -17,7 +17,6 @@ package proc
 import (
 	"fmt"
 	"io"
-	"sync"
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/sentry/context"
@@ -27,6 +26,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/fs/ramfs"
 	"gvisor.dev/gvisor/pkg/sentry/inet"
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/waiter"
 )
 
diff --git a/pkg/sentry/fs/ramfs/BUILD b/pkg/sentry/fs/ramfs/BUILD
index 012cb3e44..3fb7b0633 100644
--- a/pkg/sentry/fs/ramfs/BUILD
+++ b/pkg/sentry/fs/ramfs/BUILD
@@ -21,6 +21,7 @@ go_library(
         "//pkg/sentry/fs/fsutil",
         "//pkg/sentry/socket/unix/transport",
         "//pkg/sentry/usermem",
+        "//pkg/sync",
         "//pkg/syserror",
         "//pkg/waiter",
     ],
diff --git a/pkg/sentry/fs/ramfs/dir.go b/pkg/sentry/fs/ramfs/dir.go
index 78e082b8e..dcbb8eb2e 100644
--- a/pkg/sentry/fs/ramfs/dir.go
+++ b/pkg/sentry/fs/ramfs/dir.go
@@ -17,7 +17,6 @@ package ramfs
 
 import (
 	"fmt"
-	"sync"
 	"syscall"
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
@@ -25,6 +24,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/fs"
 	"gvisor.dev/gvisor/pkg/sentry/fs/fsutil"
 	"gvisor.dev/gvisor/pkg/sentry/socket/unix/transport"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/syserror"
 )
 
diff --git a/pkg/sentry/fs/restore.go b/pkg/sentry/fs/restore.go
index f10168125..64c6a6ae9 100644
--- a/pkg/sentry/fs/restore.go
+++ b/pkg/sentry/fs/restore.go
@@ -15,7 +15,7 @@
 package fs
 
 import (
-	"sync"
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 // RestoreEnvironment is the restore environment for file systems. It consists
diff --git a/pkg/sentry/fs/tmpfs/BUILD b/pkg/sentry/fs/tmpfs/BUILD
index 59ce400c2..3400b940c 100644
--- a/pkg/sentry/fs/tmpfs/BUILD
+++ b/pkg/sentry/fs/tmpfs/BUILD
@@ -31,6 +31,7 @@ go_library(
         "//pkg/sentry/socket/unix/transport",
         "//pkg/sentry/usage",
         "//pkg/sentry/usermem",
+        "//pkg/sync",
         "//pkg/syserror",
         "//pkg/waiter",
     ],
diff --git a/pkg/sentry/fs/tmpfs/inode_file.go b/pkg/sentry/fs/tmpfs/inode_file.go
index f86dfaa36..f1c87fe41 100644
--- a/pkg/sentry/fs/tmpfs/inode_file.go
+++ b/pkg/sentry/fs/tmpfs/inode_file.go
@@ -17,7 +17,6 @@ package tmpfs
 import (
 	"fmt"
 	"io"
-	"sync"
 	"time"
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
@@ -31,6 +30,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/safemem"
 	"gvisor.dev/gvisor/pkg/sentry/usage"
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/syserror"
 )
 
diff --git a/pkg/sentry/fs/tty/BUILD b/pkg/sentry/fs/tty/BUILD
index 95ad98cb0..f6f60d0cf 100644
--- a/pkg/sentry/fs/tty/BUILD
+++ b/pkg/sentry/fs/tty/BUILD
@@ -30,6 +30,7 @@ go_library(
         "//pkg/sentry/socket/unix/transport",
         "//pkg/sentry/unimpl",
         "//pkg/sentry/usermem",
+        "//pkg/sync",
         "//pkg/syserror",
         "//pkg/waiter",
     ],
diff --git a/pkg/sentry/fs/tty/dir.go b/pkg/sentry/fs/tty/dir.go
index 2f639c823..88aa66b24 100644
--- a/pkg/sentry/fs/tty/dir.go
+++ b/pkg/sentry/fs/tty/dir.go
@@ -19,7 +19,6 @@ import (
 	"fmt"
 	"math"
 	"strconv"
-	"sync"
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/sentry/context"
@@ -28,6 +27,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
 	"gvisor.dev/gvisor/pkg/sentry/socket/unix/transport"
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/syserror"
 	"gvisor.dev/gvisor/pkg/waiter"
 )
diff --git a/pkg/sentry/fs/tty/line_discipline.go b/pkg/sentry/fs/tty/line_discipline.go
index 7cc0eb409..894964260 100644
--- a/pkg/sentry/fs/tty/line_discipline.go
+++ b/pkg/sentry/fs/tty/line_discipline.go
@@ -16,13 +16,13 @@ package tty
 
 import (
 	"bytes"
-	"sync"
 	"unicode/utf8"
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/sentry/arch"
 	"gvisor.dev/gvisor/pkg/sentry/context"
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/syserror"
 	"gvisor.dev/gvisor/pkg/waiter"
 )
diff --git a/pkg/sentry/fs/tty/queue.go b/pkg/sentry/fs/tty/queue.go
index 231e4e6eb..8b5d4699a 100644
--- a/pkg/sentry/fs/tty/queue.go
+++ b/pkg/sentry/fs/tty/queue.go
@@ -15,13 +15,12 @@
 package tty
 
 import (
-	"sync"
-
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/sentry/arch"
 	"gvisor.dev/gvisor/pkg/sentry/context"
 	"gvisor.dev/gvisor/pkg/sentry/safemem"
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/syserror"
 	"gvisor.dev/gvisor/pkg/waiter"
 )
diff --git a/pkg/sentry/fsimpl/ext/BUILD b/pkg/sentry/fsimpl/ext/BUILD
index bc90330bc..903874141 100644
--- a/pkg/sentry/fsimpl/ext/BUILD
+++ b/pkg/sentry/fsimpl/ext/BUILD
@@ -50,6 +50,7 @@ go_library(
         "//pkg/sentry/syscalls/linux",
         "//pkg/sentry/usermem",
         "//pkg/sentry/vfs",
+        "//pkg/sync",
         "//pkg/syserror",
         "//pkg/waiter",
     ],
diff --git a/pkg/sentry/fsimpl/ext/directory.go b/pkg/sentry/fsimpl/ext/directory.go
index 91802dc1e..8944171c8 100644
--- a/pkg/sentry/fsimpl/ext/directory.go
+++ b/pkg/sentry/fsimpl/ext/directory.go
@@ -15,8 +15,6 @@
 package ext
 
 import (
-	"sync"
-
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/binary"
 	"gvisor.dev/gvisor/pkg/log"
@@ -25,6 +23,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/fsimpl/ext/disklayout"
 	"gvisor.dev/gvisor/pkg/sentry/memmap"
 	"gvisor.dev/gvisor/pkg/sentry/vfs"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/syserror"
 )
 
diff --git a/pkg/sentry/fsimpl/ext/filesystem.go b/pkg/sentry/fsimpl/ext/filesystem.go
index 616fc002a..9afb1a84c 100644
--- a/pkg/sentry/fsimpl/ext/filesystem.go
+++ b/pkg/sentry/fsimpl/ext/filesystem.go
@@ -17,13 +17,13 @@ package ext
 import (
 	"errors"
 	"io"
-	"sync"
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/fspath"
 	"gvisor.dev/gvisor/pkg/sentry/context"
 	"gvisor.dev/gvisor/pkg/sentry/fsimpl/ext/disklayout"
 	"gvisor.dev/gvisor/pkg/sentry/vfs"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/syserror"
 )
 
diff --git a/pkg/sentry/fsimpl/ext/regular_file.go b/pkg/sentry/fsimpl/ext/regular_file.go
index aec33e00a..d11153c90 100644
--- a/pkg/sentry/fsimpl/ext/regular_file.go
+++ b/pkg/sentry/fsimpl/ext/regular_file.go
@@ -16,7 +16,6 @@ package ext
 
 import (
 	"io"
-	"sync"
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/sentry/context"
@@ -24,6 +23,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/safemem"
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
 	"gvisor.dev/gvisor/pkg/sentry/vfs"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/syserror"
 )
 
diff --git a/pkg/sentry/fsimpl/kernfs/BUILD b/pkg/sentry/fsimpl/kernfs/BUILD
index 39c03ee9d..809178250 100644
--- a/pkg/sentry/fsimpl/kernfs/BUILD
+++ b/pkg/sentry/fsimpl/kernfs/BUILD
@@ -39,6 +39,7 @@ go_library(
         "//pkg/sentry/memmap",
         "//pkg/sentry/usermem",
         "//pkg/sentry/vfs",
+        "//pkg/sync",
         "//pkg/syserror",
     ],
 )
@@ -56,6 +57,7 @@ go_test(
         "//pkg/sentry/kernel/auth",
         "//pkg/sentry/usermem",
         "//pkg/sentry/vfs",
+        "//pkg/sync",
         "//pkg/syserror",
         "@com_github_google_go-cmp//cmp:go_default_library",
     ],
diff --git a/pkg/sentry/fsimpl/kernfs/inode_impl_util.go b/pkg/sentry/fsimpl/kernfs/inode_impl_util.go
index 752e0f659..1d469a0db 100644
--- a/pkg/sentry/fsimpl/kernfs/inode_impl_util.go
+++ b/pkg/sentry/fsimpl/kernfs/inode_impl_util.go
@@ -16,7 +16,6 @@ package kernfs
 
 import (
 	"fmt"
-	"sync"
 	"sync/atomic"
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
@@ -24,6 +23,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/context"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
 	"gvisor.dev/gvisor/pkg/sentry/vfs"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/syserror"
 )
 
diff --git a/pkg/sentry/fsimpl/kernfs/kernfs.go b/pkg/sentry/fsimpl/kernfs/kernfs.go
index d69b299ae..bb12f39a2 100644
--- a/pkg/sentry/fsimpl/kernfs/kernfs.go
+++ b/pkg/sentry/fsimpl/kernfs/kernfs.go
@@ -53,7 +53,6 @@ package kernfs
 
 import (
 	"fmt"
-	"sync"
 	"sync/atomic"
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
@@ -61,6 +60,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/context"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
 	"gvisor.dev/gvisor/pkg/sentry/vfs"
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 // FilesystemType implements vfs.FilesystemType.
diff --git a/pkg/sentry/fsimpl/kernfs/kernfs_test.go b/pkg/sentry/fsimpl/kernfs/kernfs_test.go
index 4b6b95f5f..5c9d580e1 100644
--- a/pkg/sentry/fsimpl/kernfs/kernfs_test.go
+++ b/pkg/sentry/fsimpl/kernfs/kernfs_test.go
@@ -19,7 +19,6 @@ import (
 	"fmt"
 	"io"
 	"runtime"
-	"sync"
 	"testing"
 
 	"github.com/google/go-cmp/cmp"
@@ -31,6 +30,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
 	"gvisor.dev/gvisor/pkg/sentry/vfs"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/syserror"
 )
 
diff --git a/pkg/sentry/fsimpl/tmpfs/BUILD b/pkg/sentry/fsimpl/tmpfs/BUILD
index a5b285987..82f5c2f41 100644
--- a/pkg/sentry/fsimpl/tmpfs/BUILD
+++ b/pkg/sentry/fsimpl/tmpfs/BUILD
@@ -47,6 +47,7 @@ go_library(
         "//pkg/sentry/usage",
         "//pkg/sentry/usermem",
         "//pkg/sentry/vfs",
+        "//pkg/sync",
         "//pkg/syserror",
     ],
 )
diff --git a/pkg/sentry/fsimpl/tmpfs/regular_file.go b/pkg/sentry/fsimpl/tmpfs/regular_file.go
index f51e247a7..f200e767d 100644
--- a/pkg/sentry/fsimpl/tmpfs/regular_file.go
+++ b/pkg/sentry/fsimpl/tmpfs/regular_file.go
@@ -17,7 +17,6 @@ package tmpfs
 import (
 	"io"
 	"math"
-	"sync"
 	"sync/atomic"
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
@@ -30,6 +29,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/usage"
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
 	"gvisor.dev/gvisor/pkg/sentry/vfs"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/syserror"
 )
 
diff --git a/pkg/sentry/fsimpl/tmpfs/tmpfs.go b/pkg/sentry/fsimpl/tmpfs/tmpfs.go
index 7be6faa5b..701826f90 100644
--- a/pkg/sentry/fsimpl/tmpfs/tmpfs.go
+++ b/pkg/sentry/fsimpl/tmpfs/tmpfs.go
@@ -26,7 +26,6 @@ package tmpfs
 import (
 	"fmt"
 	"math"
-	"sync"
 	"sync/atomic"
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
@@ -34,6 +33,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
 	"gvisor.dev/gvisor/pkg/sentry/pgalloc"
 	"gvisor.dev/gvisor/pkg/sentry/vfs"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/syserror"
 )
 
diff --git a/pkg/sentry/kernel/BUILD b/pkg/sentry/kernel/BUILD
index 2706927ff..ac85ba0c8 100644
--- a/pkg/sentry/kernel/BUILD
+++ b/pkg/sentry/kernel/BUILD
@@ -35,7 +35,7 @@ go_template_instance(
     out = "seqatomic_taskgoroutineschedinfo_unsafe.go",
     package = "kernel",
     suffix = "TaskGoroutineSchedInfo",
-    template = "//pkg/syncutil:generic_seqatomic",
+    template = "//pkg/sync:generic_seqatomic",
     types = {
         "Value": "TaskGoroutineSchedInfo",
     },
@@ -209,7 +209,7 @@ go_library(
         "//pkg/sentry/usermem",
         "//pkg/state",
         "//pkg/state/statefile",
-        "//pkg/syncutil",
+        "//pkg/sync",
         "//pkg/syserr",
         "//pkg/syserror",
         "//pkg/tcpip",
@@ -241,6 +241,7 @@ go_test(
         "//pkg/sentry/time",
         "//pkg/sentry/usage",
         "//pkg/sentry/usermem",
+        "//pkg/sync",
         "//pkg/syserror",
     ],
 )
diff --git a/pkg/sentry/kernel/abstract_socket_namespace.go b/pkg/sentry/kernel/abstract_socket_namespace.go
index 244655b5c..920fe4329 100644
--- a/pkg/sentry/kernel/abstract_socket_namespace.go
+++ b/pkg/sentry/kernel/abstract_socket_namespace.go
@@ -15,11 +15,11 @@
 package kernel
 
 import (
-	"sync"
 	"syscall"
 
 	"gvisor.dev/gvisor/pkg/refs"
 	"gvisor.dev/gvisor/pkg/sentry/socket/unix/transport"
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 // +stateify savable
diff --git a/pkg/sentry/kernel/auth/BUILD b/pkg/sentry/kernel/auth/BUILD
index 04c244447..1aa72fa47 100644
--- a/pkg/sentry/kernel/auth/BUILD
+++ b/pkg/sentry/kernel/auth/BUILD
@@ -8,7 +8,7 @@ go_template_instance(
     out = "atomicptr_credentials_unsafe.go",
     package = "auth",
     suffix = "Credentials",
-    template = "//pkg/syncutil:generic_atomicptr",
+    template = "//pkg/sync:generic_atomicptr",
     types = {
         "Value": "Credentials",
     },
@@ -64,6 +64,7 @@ go_library(
         "//pkg/bits",
         "//pkg/log",
         "//pkg/sentry/context",
+        "//pkg/sync",
         "//pkg/syserror",
     ],
 )
diff --git a/pkg/sentry/kernel/auth/user_namespace.go b/pkg/sentry/kernel/auth/user_namespace.go
index af28ccc65..9dd52c860 100644
--- a/pkg/sentry/kernel/auth/user_namespace.go
+++ b/pkg/sentry/kernel/auth/user_namespace.go
@@ -16,8 +16,8 @@ package auth
 
 import (
 	"math"
-	"sync"
 
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/syserror"
 )
 
diff --git a/pkg/sentry/kernel/epoll/BUILD b/pkg/sentry/kernel/epoll/BUILD
index 3361e8b7d..c47f6b6fc 100644
--- a/pkg/sentry/kernel/epoll/BUILD
+++ b/pkg/sentry/kernel/epoll/BUILD
@@ -32,6 +32,7 @@ go_library(
         "//pkg/sentry/fs/anon",
         "//pkg/sentry/fs/fsutil",
         "//pkg/sentry/usermem",
+        "//pkg/sync",
         "//pkg/waiter",
     ],
 )
diff --git a/pkg/sentry/kernel/epoll/epoll.go b/pkg/sentry/kernel/epoll/epoll.go
index 9c0a4e1b4..430311cc0 100644
--- a/pkg/sentry/kernel/epoll/epoll.go
+++ b/pkg/sentry/kernel/epoll/epoll.go
@@ -18,7 +18,6 @@ package epoll
 
 import (
 	"fmt"
-	"sync"
 	"syscall"
 
 	"gvisor.dev/gvisor/pkg/refs"
@@ -27,6 +26,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/fs/anon"
 	"gvisor.dev/gvisor/pkg/sentry/fs/fsutil"
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/waiter"
 )
 
diff --git a/pkg/sentry/kernel/eventfd/BUILD b/pkg/sentry/kernel/eventfd/BUILD
index e65b961e8..c831fbab2 100644
--- a/pkg/sentry/kernel/eventfd/BUILD
+++ b/pkg/sentry/kernel/eventfd/BUILD
@@ -16,6 +16,7 @@ go_library(
         "//pkg/sentry/fs/anon",
         "//pkg/sentry/fs/fsutil",
         "//pkg/sentry/usermem",
+        "//pkg/sync",
         "//pkg/syserror",
         "//pkg/waiter",
     ],
diff --git a/pkg/sentry/kernel/eventfd/eventfd.go b/pkg/sentry/kernel/eventfd/eventfd.go
index 12f0d429b..687690679 100644
--- a/pkg/sentry/kernel/eventfd/eventfd.go
+++ b/pkg/sentry/kernel/eventfd/eventfd.go
@@ -18,7 +18,6 @@ package eventfd
 
 import (
 	"math"
-	"sync"
 	"syscall"
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
@@ -28,6 +27,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/fs/anon"
 	"gvisor.dev/gvisor/pkg/sentry/fs/fsutil"
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/syserror"
 	"gvisor.dev/gvisor/pkg/waiter"
 )
diff --git a/pkg/sentry/kernel/fasync/BUILD b/pkg/sentry/kernel/fasync/BUILD
index 49d81b712..6b36bc63e 100644
--- a/pkg/sentry/kernel/fasync/BUILD
+++ b/pkg/sentry/kernel/fasync/BUILD
@@ -12,6 +12,7 @@ go_library(
         "//pkg/sentry/fs",
         "//pkg/sentry/kernel",
         "//pkg/sentry/kernel/auth",
+        "//pkg/sync",
         "//pkg/waiter",
     ],
 )
diff --git a/pkg/sentry/kernel/fasync/fasync.go b/pkg/sentry/kernel/fasync/fasync.go
index 6b0bb0324..d32c3e90a 100644
--- a/pkg/sentry/kernel/fasync/fasync.go
+++ b/pkg/sentry/kernel/fasync/fasync.go
@@ -16,12 +16,11 @@
 package fasync
 
 import (
-	"sync"
-
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/sentry/fs"
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/waiter"
 )
 
diff --git a/pkg/sentry/kernel/fd_table.go b/pkg/sentry/kernel/fd_table.go
index 11f613a11..cd1501f85 100644
--- a/pkg/sentry/kernel/fd_table.go
+++ b/pkg/sentry/kernel/fd_table.go
@@ -18,7 +18,6 @@ import (
 	"bytes"
 	"fmt"
 	"math"
-	"sync"
 	"sync/atomic"
 	"syscall"
 
@@ -28,6 +27,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/fs"
 	"gvisor.dev/gvisor/pkg/sentry/fs/lock"
 	"gvisor.dev/gvisor/pkg/sentry/limits"
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 // FDFlags define flags for an individual descriptor.
diff --git a/pkg/sentry/kernel/fd_table_test.go b/pkg/sentry/kernel/fd_table_test.go
index 2bcb6216a..eccb7d1e7 100644
--- a/pkg/sentry/kernel/fd_table_test.go
+++ b/pkg/sentry/kernel/fd_table_test.go
@@ -16,7 +16,6 @@ package kernel
 
 import (
 	"runtime"
-	"sync"
 	"testing"
 
 	"gvisor.dev/gvisor/pkg/sentry/context"
@@ -24,6 +23,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/fs"
 	"gvisor.dev/gvisor/pkg/sentry/fs/filetest"
 	"gvisor.dev/gvisor/pkg/sentry/limits"
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 const (
diff --git a/pkg/sentry/kernel/fs_context.go b/pkg/sentry/kernel/fs_context.go
index ded27d668..2448c1d99 100644
--- a/pkg/sentry/kernel/fs_context.go
+++ b/pkg/sentry/kernel/fs_context.go
@@ -16,10 +16,10 @@ package kernel
 
 import (
 	"fmt"
-	"sync"
 
 	"gvisor.dev/gvisor/pkg/refs"
 	"gvisor.dev/gvisor/pkg/sentry/fs"
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 // FSContext contains filesystem context.
diff --git a/pkg/sentry/kernel/futex/BUILD b/pkg/sentry/kernel/futex/BUILD
index 75ec31761..50db443ce 100644
--- a/pkg/sentry/kernel/futex/BUILD
+++ b/pkg/sentry/kernel/futex/BUILD
@@ -9,7 +9,7 @@ go_template_instance(
     out = "atomicptr_bucket_unsafe.go",
     package = "futex",
     suffix = "Bucket",
-    template = "//pkg/syncutil:generic_atomicptr",
+    template = "//pkg/sync:generic_atomicptr",
     types = {
         "Value": "bucket",
     },
@@ -42,6 +42,7 @@ go_library(
         "//pkg/sentry/context",
         "//pkg/sentry/memmap",
         "//pkg/sentry/usermem",
+        "//pkg/sync",
         "//pkg/syserror",
     ],
 )
@@ -51,5 +52,8 @@ go_test(
     size = "small",
     srcs = ["futex_test.go"],
     embed = [":futex"],
-    deps = ["//pkg/sentry/usermem"],
+    deps = [
+        "//pkg/sentry/usermem",
+        "//pkg/sync",
+    ],
 )
diff --git a/pkg/sentry/kernel/futex/futex.go b/pkg/sentry/kernel/futex/futex.go
index 278cc8143..d1931c8f4 100644
--- a/pkg/sentry/kernel/futex/futex.go
+++ b/pkg/sentry/kernel/futex/futex.go
@@ -18,11 +18,10 @@
 package futex
 
 import (
-	"sync"
-
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/sentry/memmap"
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/syserror"
 )
 
diff --git a/pkg/sentry/kernel/futex/futex_test.go b/pkg/sentry/kernel/futex/futex_test.go
index 65e5d1428..c23126ca5 100644
--- a/pkg/sentry/kernel/futex/futex_test.go
+++ b/pkg/sentry/kernel/futex/futex_test.go
@@ -17,13 +17,13 @@ package futex
 import (
 	"math"
 	"runtime"
-	"sync"
 	"sync/atomic"
 	"syscall"
 	"testing"
 	"unsafe"
 
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 // testData implements the Target interface, and allows us to
diff --git a/pkg/sentry/kernel/kernel.go b/pkg/sentry/kernel/kernel.go
index 8653d2f63..c85e97fef 100644
--- a/pkg/sentry/kernel/kernel.go
+++ b/pkg/sentry/kernel/kernel.go
@@ -36,7 +36,6 @@ import (
 	"fmt"
 	"io"
 	"path/filepath"
-	"sync"
 	"sync/atomic"
 	"time"
 
@@ -67,6 +66,7 @@ import (
 	uspb "gvisor.dev/gvisor/pkg/sentry/unimpl/unimplemented_syscall_go_proto"
 	"gvisor.dev/gvisor/pkg/sentry/uniqueid"
 	"gvisor.dev/gvisor/pkg/state"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/tcpip"
 )
 
diff --git a/pkg/sentry/kernel/memevent/BUILD b/pkg/sentry/kernel/memevent/BUILD
index d7a7d1169..7f36252a9 100644
--- a/pkg/sentry/kernel/memevent/BUILD
+++ b/pkg/sentry/kernel/memevent/BUILD
@@ -16,6 +16,7 @@ go_library(
         "//pkg/metric",
         "//pkg/sentry/kernel",
         "//pkg/sentry/usage",
+        "//pkg/sync",
     ],
 )
 
diff --git a/pkg/sentry/kernel/memevent/memory_events.go b/pkg/sentry/kernel/memevent/memory_events.go
index b0d98e7f0..200565bb8 100644
--- a/pkg/sentry/kernel/memevent/memory_events.go
+++ b/pkg/sentry/kernel/memevent/memory_events.go
@@ -17,7 +17,6 @@
 package memevent
 
 import (
-	"sync"
 	"time"
 
 	"gvisor.dev/gvisor/pkg/eventchannel"
@@ -26,6 +25,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
 	pb "gvisor.dev/gvisor/pkg/sentry/kernel/memevent/memory_events_go_proto"
 	"gvisor.dev/gvisor/pkg/sentry/usage"
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 var totalTicks = metric.MustCreateNewUint64Metric("/memory_events/ticks", false /*sync*/, "Total number of memory event periods that have elapsed since startup.")
diff --git a/pkg/sentry/kernel/pipe/BUILD b/pkg/sentry/kernel/pipe/BUILD
index 9d34f6d4d..5eeaeff66 100644
--- a/pkg/sentry/kernel/pipe/BUILD
+++ b/pkg/sentry/kernel/pipe/BUILD
@@ -43,6 +43,7 @@ go_library(
         "//pkg/sentry/safemem",
         "//pkg/sentry/usermem",
         "//pkg/sentry/vfs",
+        "//pkg/sync",
         "//pkg/syserror",
         "//pkg/waiter",
     ],
diff --git a/pkg/sentry/kernel/pipe/buffer.go b/pkg/sentry/kernel/pipe/buffer.go
index 95bee2d37..1c0f34269 100644
--- a/pkg/sentry/kernel/pipe/buffer.go
+++ b/pkg/sentry/kernel/pipe/buffer.go
@@ -16,9 +16,9 @@ package pipe
 
 import (
 	"io"
-	"sync"
 
 	"gvisor.dev/gvisor/pkg/sentry/safemem"
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 // buffer encapsulates a queueable byte buffer.
diff --git a/pkg/sentry/kernel/pipe/node.go b/pkg/sentry/kernel/pipe/node.go
index 4a19ab7ce..716f589af 100644
--- a/pkg/sentry/kernel/pipe/node.go
+++ b/pkg/sentry/kernel/pipe/node.go
@@ -15,12 +15,11 @@
 package pipe
 
 import (
-	"sync"
-
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/sentry/context"
 	"gvisor.dev/gvisor/pkg/sentry/fs"
 	"gvisor.dev/gvisor/pkg/sentry/fs/fsutil"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/syserror"
 )
 
diff --git a/pkg/sentry/kernel/pipe/pipe.go b/pkg/sentry/kernel/pipe/pipe.go
index 1a1b38f83..e4fd7d420 100644
--- a/pkg/sentry/kernel/pipe/pipe.go
+++ b/pkg/sentry/kernel/pipe/pipe.go
@@ -17,12 +17,12 @@ package pipe
 
 import (
 	"fmt"
-	"sync"
 	"sync/atomic"
 	"syscall"
 
 	"gvisor.dev/gvisor/pkg/sentry/context"
 	"gvisor.dev/gvisor/pkg/sentry/fs"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/syserror"
 	"gvisor.dev/gvisor/pkg/waiter"
 )
diff --git a/pkg/sentry/kernel/pipe/pipe_util.go b/pkg/sentry/kernel/pipe/pipe_util.go
index ef9641e6a..8394eb78b 100644
--- a/pkg/sentry/kernel/pipe/pipe_util.go
+++ b/pkg/sentry/kernel/pipe/pipe_util.go
@@ -17,7 +17,6 @@ package pipe
 import (
 	"io"
 	"math"
-	"sync"
 	"syscall"
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
@@ -25,6 +24,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/arch"
 	"gvisor.dev/gvisor/pkg/sentry/context"
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/waiter"
 )
 
diff --git a/pkg/sentry/kernel/pipe/vfs.go b/pkg/sentry/kernel/pipe/vfs.go
index 6416e0dd8..bf7461cbb 100644
--- a/pkg/sentry/kernel/pipe/vfs.go
+++ b/pkg/sentry/kernel/pipe/vfs.go
@@ -15,13 +15,12 @@
 package pipe
 
 import (
-	"sync"
-
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/sentry/arch"
 	"gvisor.dev/gvisor/pkg/sentry/context"
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
 	"gvisor.dev/gvisor/pkg/sentry/vfs"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/syserror"
 	"gvisor.dev/gvisor/pkg/waiter"
 )
diff --git a/pkg/sentry/kernel/semaphore/BUILD b/pkg/sentry/kernel/semaphore/BUILD
index f4c00cd86..13a961594 100644
--- a/pkg/sentry/kernel/semaphore/BUILD
+++ b/pkg/sentry/kernel/semaphore/BUILD
@@ -31,6 +31,7 @@ go_library(
         "//pkg/sentry/fs",
         "//pkg/sentry/kernel/auth",
         "//pkg/sentry/kernel/time",
+        "//pkg/sync",
         "//pkg/syserror",
     ],
 )
diff --git a/pkg/sentry/kernel/semaphore/semaphore.go b/pkg/sentry/kernel/semaphore/semaphore.go
index de9617e9d..18299814e 100644
--- a/pkg/sentry/kernel/semaphore/semaphore.go
+++ b/pkg/sentry/kernel/semaphore/semaphore.go
@@ -17,7 +17,6 @@ package semaphore
 
 import (
 	"fmt"
-	"sync"
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/log"
@@ -25,6 +24,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/fs"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
 	ktime "gvisor.dev/gvisor/pkg/sentry/kernel/time"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/syserror"
 )
 
diff --git a/pkg/sentry/kernel/shm/BUILD b/pkg/sentry/kernel/shm/BUILD
index cd48945e6..7321b22ed 100644
--- a/pkg/sentry/kernel/shm/BUILD
+++ b/pkg/sentry/kernel/shm/BUILD
@@ -24,6 +24,7 @@ go_library(
         "//pkg/sentry/platform",
         "//pkg/sentry/usage",
         "//pkg/sentry/usermem",
+        "//pkg/sync",
         "//pkg/syserror",
     ],
 )
diff --git a/pkg/sentry/kernel/shm/shm.go b/pkg/sentry/kernel/shm/shm.go
index 19034a21e..8ddef7eb8 100644
--- a/pkg/sentry/kernel/shm/shm.go
+++ b/pkg/sentry/kernel/shm/shm.go
@@ -35,7 +35,6 @@ package shm
 
 import (
 	"fmt"
-	"sync"
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/log"
@@ -49,6 +48,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/platform"
 	"gvisor.dev/gvisor/pkg/sentry/usage"
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/syserror"
 )
 
diff --git a/pkg/sentry/kernel/signal_handlers.go b/pkg/sentry/kernel/signal_handlers.go
index a16f3d57f..768fda220 100644
--- a/pkg/sentry/kernel/signal_handlers.go
+++ b/pkg/sentry/kernel/signal_handlers.go
@@ -15,10 +15,9 @@
 package kernel
 
 import (
-	"sync"
-
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/sentry/arch"
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 // SignalHandlers holds information about signal actions.
diff --git a/pkg/sentry/kernel/signalfd/BUILD b/pkg/sentry/kernel/signalfd/BUILD
index 9f7e19b4d..89e4d84b1 100644
--- a/pkg/sentry/kernel/signalfd/BUILD
+++ b/pkg/sentry/kernel/signalfd/BUILD
@@ -16,6 +16,7 @@ go_library(
         "//pkg/sentry/fs/fsutil",
         "//pkg/sentry/kernel",
         "//pkg/sentry/usermem",
+        "//pkg/sync",
         "//pkg/syserror",
         "//pkg/waiter",
     ],
diff --git a/pkg/sentry/kernel/signalfd/signalfd.go b/pkg/sentry/kernel/signalfd/signalfd.go
index 4b08d7d72..28be4a939 100644
--- a/pkg/sentry/kernel/signalfd/signalfd.go
+++ b/pkg/sentry/kernel/signalfd/signalfd.go
@@ -16,8 +16,6 @@
 package signalfd
 
 import (
-	"sync"
-
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/binary"
 	"gvisor.dev/gvisor/pkg/sentry/context"
@@ -26,6 +24,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/fs/fsutil"
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/syserror"
 	"gvisor.dev/gvisor/pkg/waiter"
 )
diff --git a/pkg/sentry/kernel/syscalls.go b/pkg/sentry/kernel/syscalls.go
index 2fdee0282..d2d01add4 100644
--- a/pkg/sentry/kernel/syscalls.go
+++ b/pkg/sentry/kernel/syscalls.go
@@ -16,13 +16,13 @@ package kernel
 
 import (
 	"fmt"
-	"sync"
 	"sync/atomic"
 
 	"gvisor.dev/gvisor/pkg/abi"
 	"gvisor.dev/gvisor/pkg/bits"
 	"gvisor.dev/gvisor/pkg/sentry/arch"
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 // maxSyscallNum is the highest supported syscall number.
diff --git a/pkg/sentry/kernel/syslog.go b/pkg/sentry/kernel/syslog.go
index 8227ecf1d..4607cde2f 100644
--- a/pkg/sentry/kernel/syslog.go
+++ b/pkg/sentry/kernel/syslog.go
@@ -17,7 +17,8 @@ package kernel
 import (
 	"fmt"
 	"math/rand"
-	"sync"
+
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 // syslog represents a sentry-global kernel log.
diff --git a/pkg/sentry/kernel/task.go b/pkg/sentry/kernel/task.go
index d25a7903b..978d66da8 100644
--- a/pkg/sentry/kernel/task.go
+++ b/pkg/sentry/kernel/task.go
@@ -17,7 +17,6 @@ package kernel
 import (
 	gocontext "context"
 	"runtime/trace"
-	"sync"
 	"sync/atomic"
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
@@ -37,7 +36,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/uniqueid"
 	"gvisor.dev/gvisor/pkg/sentry/usage"
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
-	"gvisor.dev/gvisor/pkg/syncutil"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/waiter"
 )
 
@@ -85,7 +84,7 @@ type Task struct {
 	//
 	// gosched is protected by goschedSeq. gosched is owned by the task
 	// goroutine.
-	goschedSeq syncutil.SeqCount `state:"nosave"`
+	goschedSeq sync.SeqCount `state:"nosave"`
 	gosched    TaskGoroutineSchedInfo
 
 	// yieldCount is the number of times the task goroutine has called
diff --git a/pkg/sentry/kernel/thread_group.go b/pkg/sentry/kernel/thread_group.go
index c0197a563..768e958d2 100644
--- a/pkg/sentry/kernel/thread_group.go
+++ b/pkg/sentry/kernel/thread_group.go
@@ -15,7 +15,6 @@
 package kernel
 
 import (
-	"sync"
 	"sync/atomic"
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
@@ -25,6 +24,7 @@ import (
 	ktime "gvisor.dev/gvisor/pkg/sentry/kernel/time"
 	"gvisor.dev/gvisor/pkg/sentry/limits"
 	"gvisor.dev/gvisor/pkg/sentry/usage"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/syserror"
 )
 
diff --git a/pkg/sentry/kernel/threads.go b/pkg/sentry/kernel/threads.go
index 8267929a6..bf2dabb6e 100644
--- a/pkg/sentry/kernel/threads.go
+++ b/pkg/sentry/kernel/threads.go
@@ -16,9 +16,9 @@ package kernel
 
 import (
 	"fmt"
-	"sync"
 
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/waiter"
 )
 
diff --git a/pkg/sentry/kernel/time/BUILD b/pkg/sentry/kernel/time/BUILD
index 31847e1df..4e4de0512 100644
--- a/pkg/sentry/kernel/time/BUILD
+++ b/pkg/sentry/kernel/time/BUILD
@@ -13,6 +13,7 @@ go_library(
     deps = [
         "//pkg/abi/linux",
         "//pkg/sentry/context",
+        "//pkg/sync",
         "//pkg/syserror",
         "//pkg/waiter",
     ],
diff --git a/pkg/sentry/kernel/time/time.go b/pkg/sentry/kernel/time/time.go
index 107394183..706de83ef 100644
--- a/pkg/sentry/kernel/time/time.go
+++ b/pkg/sentry/kernel/time/time.go
@@ -19,10 +19,10 @@ package time
 import (
 	"fmt"
 	"math"
-	"sync"
 	"time"
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/syserror"
 	"gvisor.dev/gvisor/pkg/waiter"
 )
diff --git a/pkg/sentry/kernel/timekeeper.go b/pkg/sentry/kernel/timekeeper.go
index 76417342a..dc99301de 100644
--- a/pkg/sentry/kernel/timekeeper.go
+++ b/pkg/sentry/kernel/timekeeper.go
@@ -16,7 +16,6 @@ package kernel
 
 import (
 	"fmt"
-	"sync"
 	"time"
 
 	"gvisor.dev/gvisor/pkg/log"
@@ -24,6 +23,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/pgalloc"
 	"gvisor.dev/gvisor/pkg/sentry/platform"
 	sentrytime "gvisor.dev/gvisor/pkg/sentry/time"
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 // Timekeeper manages all of the kernel clocks.
diff --git a/pkg/sentry/kernel/tty.go b/pkg/sentry/kernel/tty.go
index 048de26dc..464d2306a 100644
--- a/pkg/sentry/kernel/tty.go
+++ b/pkg/sentry/kernel/tty.go
@@ -14,7 +14,7 @@
 
 package kernel
 
-import "sync"
+import "gvisor.dev/gvisor/pkg/sync"
 
 // TTY defines the relationship between a thread group and its controlling
 // terminal.
diff --git a/pkg/sentry/kernel/uts_namespace.go b/pkg/sentry/kernel/uts_namespace.go
index 0a563e715..8ccf04bd1 100644
--- a/pkg/sentry/kernel/uts_namespace.go
+++ b/pkg/sentry/kernel/uts_namespace.go
@@ -15,9 +15,8 @@
 package kernel
 
 import (
-	"sync"
-
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 // UTSNamespace represents a UTS namespace, a holder of two system identifiers:
diff --git a/pkg/sentry/limits/BUILD b/pkg/sentry/limits/BUILD
index 156e67bf8..9fa841e8b 100644
--- a/pkg/sentry/limits/BUILD
+++ b/pkg/sentry/limits/BUILD
@@ -15,6 +15,7 @@ go_library(
     deps = [
         "//pkg/abi/linux",
         "//pkg/sentry/context",
+        "//pkg/sync",
     ],
 )
 
diff --git a/pkg/sentry/limits/limits.go b/pkg/sentry/limits/limits.go
index b6c22656b..31b9e9ff6 100644
--- a/pkg/sentry/limits/limits.go
+++ b/pkg/sentry/limits/limits.go
@@ -16,8 +16,9 @@
 package limits
 
 import (
-	"sync"
 	"syscall"
+
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 // LimitType defines a type of resource limit.
diff --git a/pkg/sentry/mm/BUILD b/pkg/sentry/mm/BUILD
index 839931f67..83e248431 100644
--- a/pkg/sentry/mm/BUILD
+++ b/pkg/sentry/mm/BUILD
@@ -118,7 +118,7 @@ go_library(
         "//pkg/sentry/safemem",
         "//pkg/sentry/usage",
         "//pkg/sentry/usermem",
-        "//pkg/syncutil",
+        "//pkg/sync",
         "//pkg/syserror",
         "//pkg/tcpip/buffer",
     ],
diff --git a/pkg/sentry/mm/aio_context.go b/pkg/sentry/mm/aio_context.go
index 1b746d030..4b48866ad 100644
--- a/pkg/sentry/mm/aio_context.go
+++ b/pkg/sentry/mm/aio_context.go
@@ -15,8 +15,6 @@
 package mm
 
 import (
-	"sync"
-
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/refs"
 	"gvisor.dev/gvisor/pkg/sentry/context"
@@ -25,6 +23,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/platform"
 	"gvisor.dev/gvisor/pkg/sentry/usage"
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/syserror"
 )
 
diff --git a/pkg/sentry/mm/mm.go b/pkg/sentry/mm/mm.go
index 58a5c186d..fa86ebced 100644
--- a/pkg/sentry/mm/mm.go
+++ b/pkg/sentry/mm/mm.go
@@ -35,8 +35,6 @@
 package mm
 
 import (
-	"sync"
-
 	"gvisor.dev/gvisor/pkg/sentry/arch"
 	"gvisor.dev/gvisor/pkg/sentry/fs"
 	"gvisor.dev/gvisor/pkg/sentry/memmap"
@@ -44,7 +42,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/platform"
 	"gvisor.dev/gvisor/pkg/sentry/safemem"
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
-	"gvisor.dev/gvisor/pkg/syncutil"
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 // MemoryManager implements a virtual address space.
@@ -82,7 +80,7 @@ type MemoryManager struct {
 	users int32
 
 	// mappingMu is analogous to Linux's struct mm_struct::mmap_sem.
-	mappingMu syncutil.DowngradableRWMutex `state:"nosave"`
+	mappingMu sync.DowngradableRWMutex `state:"nosave"`
 
 	// vmas stores virtual memory areas. Since vmas are stored by value,
 	// clients should usually use vmaIterator.ValuePtr() instead of
@@ -125,7 +123,7 @@ type MemoryManager struct {
 
 	// activeMu is loosely analogous to Linux's struct
 	// mm_struct::page_table_lock.
-	activeMu syncutil.DowngradableRWMutex `state:"nosave"`
+	activeMu sync.DowngradableRWMutex `state:"nosave"`
 
 	// pmas stores platform mapping areas used to implement vmas. Since pmas
 	// are stored by value, clients should usually use pmaIterator.ValuePtr()
diff --git a/pkg/sentry/pgalloc/BUILD b/pkg/sentry/pgalloc/BUILD
index f404107af..a9a2642c5 100644
--- a/pkg/sentry/pgalloc/BUILD
+++ b/pkg/sentry/pgalloc/BUILD
@@ -73,6 +73,7 @@ go_library(
         "//pkg/sentry/usage",
         "//pkg/sentry/usermem",
         "//pkg/state",
+        "//pkg/sync",
         "//pkg/syserror",
     ],
 )
diff --git a/pkg/sentry/pgalloc/pgalloc.go b/pkg/sentry/pgalloc/pgalloc.go
index f7f7298c4..c99e023d9 100644
--- a/pkg/sentry/pgalloc/pgalloc.go
+++ b/pkg/sentry/pgalloc/pgalloc.go
@@ -25,7 +25,6 @@ import (
 	"fmt"
 	"math"
 	"os"
-	"sync"
 	"sync/atomic"
 	"syscall"
 	"time"
@@ -37,6 +36,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/safemem"
 	"gvisor.dev/gvisor/pkg/sentry/usage"
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/syserror"
 )
 
diff --git a/pkg/sentry/platform/interrupt/BUILD b/pkg/sentry/platform/interrupt/BUILD
index b6d008dbe..85e882df9 100644
--- a/pkg/sentry/platform/interrupt/BUILD
+++ b/pkg/sentry/platform/interrupt/BUILD
@@ -10,6 +10,7 @@ go_library(
     ],
     importpath = "gvisor.dev/gvisor/pkg/sentry/platform/interrupt",
     visibility = ["//pkg/sentry:internal"],
+    deps = ["//pkg/sync"],
 )
 
 go_test(
diff --git a/pkg/sentry/platform/interrupt/interrupt.go b/pkg/sentry/platform/interrupt/interrupt.go
index a4651f500..57be41647 100644
--- a/pkg/sentry/platform/interrupt/interrupt.go
+++ b/pkg/sentry/platform/interrupt/interrupt.go
@@ -17,7 +17,8 @@ package interrupt
 
 import (
 	"fmt"
-	"sync"
+
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 // Receiver receives interrupt notifications from a Forwarder.
diff --git a/pkg/sentry/platform/kvm/BUILD b/pkg/sentry/platform/kvm/BUILD
index f3afd98da..6a358d1d4 100644
--- a/pkg/sentry/platform/kvm/BUILD
+++ b/pkg/sentry/platform/kvm/BUILD
@@ -55,6 +55,7 @@ go_library(
         "//pkg/sentry/platform/safecopy",
         "//pkg/sentry/time",
         "//pkg/sentry/usermem",
+        "//pkg/sync",
     ],
 )
 
diff --git a/pkg/sentry/platform/kvm/address_space.go b/pkg/sentry/platform/kvm/address_space.go
index ea8b9632e..a25f3c449 100644
--- a/pkg/sentry/platform/kvm/address_space.go
+++ b/pkg/sentry/platform/kvm/address_space.go
@@ -15,13 +15,13 @@
 package kvm
 
 import (
-	"sync"
 	"sync/atomic"
 
 	"gvisor.dev/gvisor/pkg/atomicbitops"
 	"gvisor.dev/gvisor/pkg/sentry/platform"
 	"gvisor.dev/gvisor/pkg/sentry/platform/ring0/pagetables"
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 // dirtySet tracks vCPUs for invalidation.
diff --git a/pkg/sentry/platform/kvm/bluepill_arm64_unsafe.go b/pkg/sentry/platform/kvm/bluepill_arm64_unsafe.go
index e5fac0d6a..2f02c03cf 100644
--- a/pkg/sentry/platform/kvm/bluepill_arm64_unsafe.go
+++ b/pkg/sentry/platform/kvm/bluepill_arm64_unsafe.go
@@ -17,8 +17,6 @@
 package kvm
 
 import (
-	"unsafe"
-
 	"gvisor.dev/gvisor/pkg/sentry/arch"
 )
 
diff --git a/pkg/sentry/platform/kvm/kvm.go b/pkg/sentry/platform/kvm/kvm.go
index f2c2c059e..a7850faed 100644
--- a/pkg/sentry/platform/kvm/kvm.go
+++ b/pkg/sentry/platform/kvm/kvm.go
@@ -18,13 +18,13 @@ package kvm
 import (
 	"fmt"
 	"os"
-	"sync"
 	"syscall"
 
 	"gvisor.dev/gvisor/pkg/sentry/platform"
 	"gvisor.dev/gvisor/pkg/sentry/platform/ring0"
 	"gvisor.dev/gvisor/pkg/sentry/platform/ring0/pagetables"
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 // KVM represents a lightweight VM context.
diff --git a/pkg/sentry/platform/kvm/machine.go b/pkg/sentry/platform/kvm/machine.go
index 7d02ebf19..e6d912168 100644
--- a/pkg/sentry/platform/kvm/machine.go
+++ b/pkg/sentry/platform/kvm/machine.go
@@ -17,7 +17,6 @@ package kvm
 import (
 	"fmt"
 	"runtime"
-	"sync"
 	"sync/atomic"
 	"syscall"
 
@@ -27,6 +26,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/platform/ring0"
 	"gvisor.dev/gvisor/pkg/sentry/platform/ring0/pagetables"
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 // machine contains state associated with the VM as a whole.
diff --git a/pkg/sentry/platform/ptrace/BUILD b/pkg/sentry/platform/ptrace/BUILD
index 0df8cfa0f..cd13390c3 100644
--- a/pkg/sentry/platform/ptrace/BUILD
+++ b/pkg/sentry/platform/ptrace/BUILD
@@ -33,6 +33,7 @@ go_library(
         "//pkg/sentry/platform/interrupt",
         "//pkg/sentry/platform/safecopy",
         "//pkg/sentry/usermem",
+        "//pkg/sync",
         "@org_golang_x_sys//unix:go_default_library",
     ],
 )
diff --git a/pkg/sentry/platform/ptrace/ptrace.go b/pkg/sentry/platform/ptrace/ptrace.go
index 7b120a15d..bb0e03880 100644
--- a/pkg/sentry/platform/ptrace/ptrace.go
+++ b/pkg/sentry/platform/ptrace/ptrace.go
@@ -46,13 +46,13 @@ package ptrace
 
 import (
 	"os"
-	"sync"
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/sentry/arch"
 	"gvisor.dev/gvisor/pkg/sentry/platform"
 	"gvisor.dev/gvisor/pkg/sentry/platform/interrupt"
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 var (
diff --git a/pkg/sentry/platform/ptrace/subprocess.go b/pkg/sentry/platform/ptrace/subprocess.go
index 20244fd95..15dc46a5b 100644
--- a/pkg/sentry/platform/ptrace/subprocess.go
+++ b/pkg/sentry/platform/ptrace/subprocess.go
@@ -18,7 +18,6 @@ import (
 	"fmt"
 	"os"
 	"runtime"
-	"sync"
 	"syscall"
 
 	"golang.org/x/sys/unix"
@@ -27,6 +26,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/arch"
 	"gvisor.dev/gvisor/pkg/sentry/platform"
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 // Linux kernel errnos which "should never be seen by user programs", but will
diff --git a/pkg/sentry/platform/ptrace/subprocess_linux_unsafe.go b/pkg/sentry/platform/ptrace/subprocess_linux_unsafe.go
index 2e6fbe488..245b20722 100644
--- a/pkg/sentry/platform/ptrace/subprocess_linux_unsafe.go
+++ b/pkg/sentry/platform/ptrace/subprocess_linux_unsafe.go
@@ -18,7 +18,6 @@
 package ptrace
 
 import (
-	"sync"
 	"sync/atomic"
 	"syscall"
 	"unsafe"
@@ -26,6 +25,7 @@ import (
 	"golang.org/x/sys/unix"
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/sentry/hostcpu"
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 // maskPool contains reusable CPU masks for setting affinity. Unfortunately,
diff --git a/pkg/sentry/platform/ring0/defs.go b/pkg/sentry/platform/ring0/defs.go
index 3f094c2a7..86fd5ed58 100644
--- a/pkg/sentry/platform/ring0/defs.go
+++ b/pkg/sentry/platform/ring0/defs.go
@@ -17,7 +17,7 @@ package ring0
 import (
 	"syscall"
 
-	"gvisor.dev/gvisor/pkg/sentry/usermem"
+	"gvisor.dev/gvisor/pkg/sentry/platform/ring0/pagetables"
 )
 
 // Kernel is a global kernel object.
diff --git a/pkg/sentry/platform/ring0/defs_amd64.go b/pkg/sentry/platform/ring0/defs_amd64.go
index 10dbd381f..9dae0dccb 100644
--- a/pkg/sentry/platform/ring0/defs_amd64.go
+++ b/pkg/sentry/platform/ring0/defs_amd64.go
@@ -18,6 +18,7 @@ package ring0
 
 import (
 	"gvisor.dev/gvisor/pkg/sentry/platform/ring0/pagetables"
+	"gvisor.dev/gvisor/pkg/sentry/usermem"
 )
 
 var (
diff --git a/pkg/sentry/platform/ring0/defs_arm64.go b/pkg/sentry/platform/ring0/defs_arm64.go
index dc0eeec01..a850ce6cf 100644
--- a/pkg/sentry/platform/ring0/defs_arm64.go
+++ b/pkg/sentry/platform/ring0/defs_arm64.go
@@ -18,6 +18,7 @@ package ring0
 
 import (
 	"gvisor.dev/gvisor/pkg/sentry/platform/ring0/pagetables"
+	"gvisor.dev/gvisor/pkg/sentry/usermem"
 )
 
 var (
diff --git a/pkg/sentry/platform/ring0/pagetables/BUILD b/pkg/sentry/platform/ring0/pagetables/BUILD
index e2e15ba5c..387a7f6c3 100644
--- a/pkg/sentry/platform/ring0/pagetables/BUILD
+++ b/pkg/sentry/platform/ring0/pagetables/BUILD
@@ -96,7 +96,10 @@ go_library(
         "//pkg/sentry/platform/kvm:__subpackages__",
         "//pkg/sentry/platform/ring0:__subpackages__",
     ],
-    deps = ["//pkg/sentry/usermem"],
+    deps = [
+        "//pkg/sentry/usermem",
+        "//pkg/sync",
+    ],
 )
 
 go_test(
diff --git a/pkg/sentry/platform/ring0/pagetables/pcids_x86.go b/pkg/sentry/platform/ring0/pagetables/pcids_x86.go
index 0f029f25d..e199bae18 100644
--- a/pkg/sentry/platform/ring0/pagetables/pcids_x86.go
+++ b/pkg/sentry/platform/ring0/pagetables/pcids_x86.go
@@ -17,7 +17,7 @@
 package pagetables
 
 import (
-	"sync"
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 // limitPCID is the number of valid PCIDs.
diff --git a/pkg/sentry/socket/netlink/BUILD b/pkg/sentry/socket/netlink/BUILD
index 136821963..103933144 100644
--- a/pkg/sentry/socket/netlink/BUILD
+++ b/pkg/sentry/socket/netlink/BUILD
@@ -27,6 +27,7 @@ go_library(
         "//pkg/sentry/socket/unix",
         "//pkg/sentry/socket/unix/transport",
         "//pkg/sentry/usermem",
+        "//pkg/sync",
         "//pkg/syserr",
         "//pkg/syserror",
         "//pkg/tcpip",
diff --git a/pkg/sentry/socket/netlink/port/BUILD b/pkg/sentry/socket/netlink/port/BUILD
index 463544c1a..2d9f4ba9b 100644
--- a/pkg/sentry/socket/netlink/port/BUILD
+++ b/pkg/sentry/socket/netlink/port/BUILD
@@ -8,6 +8,7 @@ go_library(
     srcs = ["port.go"],
     importpath = "gvisor.dev/gvisor/pkg/sentry/socket/netlink/port",
     visibility = ["//pkg/sentry:internal"],
+    deps = ["//pkg/sync"],
 )
 
 go_test(
diff --git a/pkg/sentry/socket/netlink/port/port.go b/pkg/sentry/socket/netlink/port/port.go
index e9d3275b1..2cd3afc22 100644
--- a/pkg/sentry/socket/netlink/port/port.go
+++ b/pkg/sentry/socket/netlink/port/port.go
@@ -24,7 +24,8 @@ import (
 	"fmt"
 	"math"
 	"math/rand"
-	"sync"
+
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 // maxPorts is a sanity limit on the maximum number of ports to allocate per
diff --git a/pkg/sentry/socket/netlink/socket.go b/pkg/sentry/socket/netlink/socket.go
index d2e3644a6..cea56f4ed 100644
--- a/pkg/sentry/socket/netlink/socket.go
+++ b/pkg/sentry/socket/netlink/socket.go
@@ -17,7 +17,6 @@ package netlink
 
 import (
 	"math"
-	"sync"
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/binary"
@@ -34,6 +33,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/socket/unix"
 	"gvisor.dev/gvisor/pkg/sentry/socket/unix/transport"
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/syserr"
 	"gvisor.dev/gvisor/pkg/syserror"
 	"gvisor.dev/gvisor/pkg/tcpip"
diff --git a/pkg/sentry/socket/netstack/BUILD b/pkg/sentry/socket/netstack/BUILD
index e414d8055..f78784569 100644
--- a/pkg/sentry/socket/netstack/BUILD
+++ b/pkg/sentry/socket/netstack/BUILD
@@ -34,6 +34,7 @@ go_library(
         "//pkg/sentry/socket/netfilter",
         "//pkg/sentry/unimpl",
         "//pkg/sentry/usermem",
+        "//pkg/sync",
         "//pkg/syserr",
         "//pkg/syserror",
         "//pkg/tcpip",
diff --git a/pkg/sentry/socket/netstack/netstack.go b/pkg/sentry/socket/netstack/netstack.go
index 764f11a6b..0affb8071 100644
--- a/pkg/sentry/socket/netstack/netstack.go
+++ b/pkg/sentry/socket/netstack/netstack.go
@@ -29,7 +29,6 @@ import (
 	"io"
 	"math"
 	"reflect"
-	"sync"
 	"syscall"
 	"time"
 
@@ -49,6 +48,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/socket/netfilter"
 	"gvisor.dev/gvisor/pkg/sentry/unimpl"
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/syserr"
 	"gvisor.dev/gvisor/pkg/syserror"
 	"gvisor.dev/gvisor/pkg/tcpip"
diff --git a/pkg/sentry/socket/rpcinet/conn/BUILD b/pkg/sentry/socket/rpcinet/conn/BUILD
index 23eadcb1b..b2677c659 100644
--- a/pkg/sentry/socket/rpcinet/conn/BUILD
+++ b/pkg/sentry/socket/rpcinet/conn/BUILD
@@ -10,6 +10,7 @@ go_library(
     deps = [
         "//pkg/binary",
         "//pkg/sentry/socket/rpcinet:syscall_rpc_go_proto",
+        "//pkg/sync",
         "//pkg/syserr",
         "//pkg/unet",
         "@com_github_golang_protobuf//proto:go_default_library",
diff --git a/pkg/sentry/socket/rpcinet/conn/conn.go b/pkg/sentry/socket/rpcinet/conn/conn.go
index 356adad99..02f39c767 100644
--- a/pkg/sentry/socket/rpcinet/conn/conn.go
+++ b/pkg/sentry/socket/rpcinet/conn/conn.go
@@ -17,12 +17,12 @@ package conn
 
 import (
 	"fmt"
-	"sync"
 	"sync/atomic"
 	"syscall"
 
 	"github.com/golang/protobuf/proto"
 	"gvisor.dev/gvisor/pkg/binary"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/syserr"
 	"gvisor.dev/gvisor/pkg/unet"
 
diff --git a/pkg/sentry/socket/rpcinet/notifier/BUILD b/pkg/sentry/socket/rpcinet/notifier/BUILD
index a3585e10d..a5954f22b 100644
--- a/pkg/sentry/socket/rpcinet/notifier/BUILD
+++ b/pkg/sentry/socket/rpcinet/notifier/BUILD
@@ -10,6 +10,7 @@ go_library(
     deps = [
         "//pkg/sentry/socket/rpcinet:syscall_rpc_go_proto",
         "//pkg/sentry/socket/rpcinet/conn",
+        "//pkg/sync",
         "//pkg/waiter",
         "@org_golang_x_sys//unix:go_default_library",
     ],
diff --git a/pkg/sentry/socket/rpcinet/notifier/notifier.go b/pkg/sentry/socket/rpcinet/notifier/notifier.go
index 7efe4301f..82b75d6dd 100644
--- a/pkg/sentry/socket/rpcinet/notifier/notifier.go
+++ b/pkg/sentry/socket/rpcinet/notifier/notifier.go
@@ -17,12 +17,12 @@ package notifier
 
 import (
 	"fmt"
-	"sync"
 	"syscall"
 
 	"golang.org/x/sys/unix"
 	"gvisor.dev/gvisor/pkg/sentry/socket/rpcinet/conn"
 	pb "gvisor.dev/gvisor/pkg/sentry/socket/rpcinet/syscall_rpc_go_proto"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/waiter"
 )
 
diff --git a/pkg/sentry/socket/unix/transport/BUILD b/pkg/sentry/socket/unix/transport/BUILD
index 788ad70d2..d7ba95dff 100644
--- a/pkg/sentry/socket/unix/transport/BUILD
+++ b/pkg/sentry/socket/unix/transport/BUILD
@@ -32,6 +32,7 @@ go_library(
         "//pkg/ilist",
         "//pkg/refs",
         "//pkg/sentry/context",
+        "//pkg/sync",
         "//pkg/syserr",
         "//pkg/tcpip",
         "//pkg/tcpip/buffer",
diff --git a/pkg/sentry/socket/unix/transport/connectioned.go b/pkg/sentry/socket/unix/transport/connectioned.go
index dea11e253..9e6fbc111 100644
--- a/pkg/sentry/socket/unix/transport/connectioned.go
+++ b/pkg/sentry/socket/unix/transport/connectioned.go
@@ -15,10 +15,9 @@
 package transport
 
 import (
-	"sync"
-
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/sentry/context"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/syserr"
 	"gvisor.dev/gvisor/pkg/tcpip"
 	"gvisor.dev/gvisor/pkg/waiter"
diff --git a/pkg/sentry/socket/unix/transport/queue.go b/pkg/sentry/socket/unix/transport/queue.go
index e27b1c714..5dcd3d95e 100644
--- a/pkg/sentry/socket/unix/transport/queue.go
+++ b/pkg/sentry/socket/unix/transport/queue.go
@@ -15,9 +15,8 @@
 package transport
 
 import (
-	"sync"
-
 	"gvisor.dev/gvisor/pkg/refs"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/syserr"
 	"gvisor.dev/gvisor/pkg/waiter"
 )
diff --git a/pkg/sentry/socket/unix/transport/unix.go b/pkg/sentry/socket/unix/transport/unix.go
index 37c7ac3c1..fcc0da332 100644
--- a/pkg/sentry/socket/unix/transport/unix.go
+++ b/pkg/sentry/socket/unix/transport/unix.go
@@ -16,11 +16,11 @@
 package transport
 
 import (
-	"sync"
 	"sync/atomic"
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/sentry/context"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/syserr"
 	"gvisor.dev/gvisor/pkg/tcpip"
 	"gvisor.dev/gvisor/pkg/tcpip/buffer"
diff --git a/pkg/sentry/syscalls/linux/BUILD b/pkg/sentry/syscalls/linux/BUILD
index a76975cee..aa05e208a 100644
--- a/pkg/sentry/syscalls/linux/BUILD
+++ b/pkg/sentry/syscalls/linux/BUILD
@@ -91,6 +91,7 @@ go_library(
         "//pkg/sentry/syscalls",
         "//pkg/sentry/usage",
         "//pkg/sentry/usermem",
+        "//pkg/sync",
         "//pkg/syserr",
         "//pkg/syserror",
         "//pkg/waiter",
diff --git a/pkg/sentry/syscalls/linux/error.go b/pkg/sentry/syscalls/linux/error.go
index 1d9018c96..60469549d 100644
--- a/pkg/sentry/syscalls/linux/error.go
+++ b/pkg/sentry/syscalls/linux/error.go
@@ -16,13 +16,13 @@ package linux
 
 import (
 	"io"
-	"sync"
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/log"
 	"gvisor.dev/gvisor/pkg/metric"
 	"gvisor.dev/gvisor/pkg/sentry/fs"
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/syserror"
 )
 
diff --git a/pkg/sentry/time/BUILD b/pkg/sentry/time/BUILD
index 18e212dff..3cde3a0be 100644
--- a/pkg/sentry/time/BUILD
+++ b/pkg/sentry/time/BUILD
@@ -9,7 +9,7 @@ go_template_instance(
     out = "seqatomic_parameters_unsafe.go",
     package = "time",
     suffix = "Parameters",
-    template = "//pkg/syncutil:generic_seqatomic",
+    template = "//pkg/sync:generic_seqatomic",
     types = {
         "Value": "Parameters",
     },
@@ -36,7 +36,7 @@ go_library(
     deps = [
         "//pkg/log",
         "//pkg/metric",
-        "//pkg/syncutil",
+        "//pkg/sync",
         "//pkg/syserror",
     ],
 )
diff --git a/pkg/sentry/time/calibrated_clock.go b/pkg/sentry/time/calibrated_clock.go
index 318503277..f9a93115d 100644
--- a/pkg/sentry/time/calibrated_clock.go
+++ b/pkg/sentry/time/calibrated_clock.go
@@ -17,11 +17,11 @@
 package time
 
 import (
-	"sync"
 	"time"
 
 	"gvisor.dev/gvisor/pkg/log"
 	"gvisor.dev/gvisor/pkg/metric"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/syserror"
 )
 
diff --git a/pkg/sentry/usage/BUILD b/pkg/sentry/usage/BUILD
index c32fe3241..5518ac3d0 100644
--- a/pkg/sentry/usage/BUILD
+++ b/pkg/sentry/usage/BUILD
@@ -18,5 +18,6 @@ go_library(
     deps = [
         "//pkg/bits",
         "//pkg/memutil",
+        "//pkg/sync",
     ],
 )
diff --git a/pkg/sentry/usage/memory.go b/pkg/sentry/usage/memory.go
index d6ef644d8..538c645eb 100644
--- a/pkg/sentry/usage/memory.go
+++ b/pkg/sentry/usage/memory.go
@@ -17,12 +17,12 @@ package usage
 import (
 	"fmt"
 	"os"
-	"sync"
 	"sync/atomic"
 	"syscall"
 
 	"gvisor.dev/gvisor/pkg/bits"
 	"gvisor.dev/gvisor/pkg/memutil"
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 // MemoryKind represents a type of memory used by the application.
diff --git a/pkg/sentry/vfs/BUILD b/pkg/sentry/vfs/BUILD
index 4c6aa04a1..35c7be259 100644
--- a/pkg/sentry/vfs/BUILD
+++ b/pkg/sentry/vfs/BUILD
@@ -34,7 +34,7 @@ go_library(
         "//pkg/sentry/kernel/auth",
         "//pkg/sentry/memmap",
         "//pkg/sentry/usermem",
-        "//pkg/syncutil",
+        "//pkg/sync",
         "//pkg/syserror",
         "//pkg/waiter",
     ],
@@ -54,6 +54,7 @@ go_test(
         "//pkg/sentry/context/contexttest",
         "//pkg/sentry/kernel/auth",
         "//pkg/sentry/usermem",
+        "//pkg/sync",
         "//pkg/syserror",
     ],
 )
diff --git a/pkg/sentry/vfs/dentry.go b/pkg/sentry/vfs/dentry.go
index 1bc9c4a38..486a76475 100644
--- a/pkg/sentry/vfs/dentry.go
+++ b/pkg/sentry/vfs/dentry.go
@@ -16,9 +16,9 @@ package vfs
 
 import (
 	"fmt"
-	"sync"
 	"sync/atomic"
 
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/syserror"
 )
 
diff --git a/pkg/sentry/vfs/file_description_impl_util.go b/pkg/sentry/vfs/file_description_impl_util.go
index 66eb57bc2..c00b3c84b 100644
--- a/pkg/sentry/vfs/file_description_impl_util.go
+++ b/pkg/sentry/vfs/file_description_impl_util.go
@@ -17,13 +17,13 @@ package vfs
 import (
 	"bytes"
 	"io"
-	"sync"
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/sentry/arch"
 	"gvisor.dev/gvisor/pkg/sentry/context"
 	"gvisor.dev/gvisor/pkg/sentry/memmap"
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/syserror"
 	"gvisor.dev/gvisor/pkg/waiter"
 )
diff --git a/pkg/sentry/vfs/mount_test.go b/pkg/sentry/vfs/mount_test.go
index adff0b94b..3b933468d 100644
--- a/pkg/sentry/vfs/mount_test.go
+++ b/pkg/sentry/vfs/mount_test.go
@@ -17,8 +17,9 @@ package vfs
 import (
 	"fmt"
 	"runtime"
-	"sync"
 	"testing"
+
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 func TestMountTableLookupEmpty(t *testing.T) {
diff --git a/pkg/sentry/vfs/mount_unsafe.go b/pkg/sentry/vfs/mount_unsafe.go
index ab13fa461..bd90d36c4 100644
--- a/pkg/sentry/vfs/mount_unsafe.go
+++ b/pkg/sentry/vfs/mount_unsafe.go
@@ -26,7 +26,7 @@ import (
 	"sync/atomic"
 	"unsafe"
 
-	"gvisor.dev/gvisor/pkg/syncutil"
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 // mountKey represents the location at which a Mount is mounted. It is
@@ -75,7 +75,7 @@ type mountTable struct {
 	// intrinsics and inline assembly, limiting the performance of this
 	// approach.)
 
-	seq  syncutil.SeqCount
+	seq  sync.SeqCount
 	seed uint32 // for hashing keys
 
 	// size holds both length (number of elements) and capacity (number of
diff --git a/pkg/sentry/vfs/pathname.go b/pkg/sentry/vfs/pathname.go
index 8e155654f..cf80df90e 100644
--- a/pkg/sentry/vfs/pathname.go
+++ b/pkg/sentry/vfs/pathname.go
@@ -15,10 +15,9 @@
 package vfs
 
 import (
-	"sync"
-
 	"gvisor.dev/gvisor/pkg/fspath"
 	"gvisor.dev/gvisor/pkg/sentry/context"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/syserror"
 )
 
diff --git a/pkg/sentry/vfs/resolving_path.go b/pkg/sentry/vfs/resolving_path.go
index f0641d314..8a0b382f6 100644
--- a/pkg/sentry/vfs/resolving_path.go
+++ b/pkg/sentry/vfs/resolving_path.go
@@ -16,11 +16,11 @@ package vfs
 
 import (
 	"fmt"
-	"sync"
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/fspath"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/syserror"
 )
 
diff --git a/pkg/sentry/vfs/vfs.go b/pkg/sentry/vfs/vfs.go
index ea2db7031..1f21b0b31 100644
--- a/pkg/sentry/vfs/vfs.go
+++ b/pkg/sentry/vfs/vfs.go
@@ -29,12 +29,12 @@ package vfs
 
 import (
 	"fmt"
-	"sync"
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/fspath"
 	"gvisor.dev/gvisor/pkg/sentry/context"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/syserror"
 )
 
diff --git a/pkg/sentry/watchdog/BUILD b/pkg/sentry/watchdog/BUILD
index 4d8435265..28f21f13d 100644
--- a/pkg/sentry/watchdog/BUILD
+++ b/pkg/sentry/watchdog/BUILD
@@ -13,5 +13,6 @@ go_library(
         "//pkg/metric",
         "//pkg/sentry/kernel",
         "//pkg/sentry/kernel/time",
+        "//pkg/sync",
     ],
 )
diff --git a/pkg/sentry/watchdog/watchdog.go b/pkg/sentry/watchdog/watchdog.go
index 5e4611333..bfb2fac26 100644
--- a/pkg/sentry/watchdog/watchdog.go
+++ b/pkg/sentry/watchdog/watchdog.go
@@ -32,7 +32,6 @@ package watchdog
 import (
 	"bytes"
 	"fmt"
-	"sync"
 	"time"
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
@@ -40,6 +39,7 @@ import (
 	"gvisor.dev/gvisor/pkg/metric"
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
 	ktime "gvisor.dev/gvisor/pkg/sentry/kernel/time"
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 // Opts configures the watchdog.
diff --git a/pkg/sync/BUILD b/pkg/sync/BUILD
new file mode 100644
index 000000000..e8cd16b8f
--- /dev/null
+++ b/pkg/sync/BUILD
@@ -0,0 +1,53 @@
+load("//tools/go_stateify:defs.bzl", "go_library")
+load("@io_bazel_rules_go//go:def.bzl", "go_test")
+load("//tools/go_generics:defs.bzl", "go_template")
+
+package(
+    default_visibility = ["//:sandbox"],
+    licenses = ["notice"],
+)
+
+exports_files(["LICENSE"])
+
+go_template(
+    name = "generic_atomicptr",
+    srcs = ["atomicptr_unsafe.go"],
+    types = [
+        "Value",
+    ],
+)
+
+go_template(
+    name = "generic_seqatomic",
+    srcs = ["seqatomic_unsafe.go"],
+    types = [
+        "Value",
+    ],
+    deps = [
+        ":sync",
+    ],
+)
+
+go_library(
+    name = "sync",
+    srcs = [
+        "aliases.go",
+        "downgradable_rwmutex_unsafe.go",
+        "memmove_unsafe.go",
+        "norace_unsafe.go",
+        "race_unsafe.go",
+        "seqcount.go",
+        "syncutil.go",
+    ],
+    importpath = "gvisor.dev/gvisor/pkg/sync",
+)
+
+go_test(
+    name = "sync_test",
+    size = "small",
+    srcs = [
+        "downgradable_rwmutex_test.go",
+        "seqcount_test.go",
+    ],
+    embed = [":sync"],
+)
diff --git a/pkg/sync/LICENSE b/pkg/sync/LICENSE
new file mode 100644
index 000000000..6a66aea5e
--- /dev/null
+++ b/pkg/sync/LICENSE
@@ -0,0 +1,27 @@
+Copyright (c) 2009 The Go Authors. All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are
+met:
+
+   * Redistributions of source code must retain the above copyright
+notice, this list of conditions and the following disclaimer.
+   * Redistributions in binary form must reproduce the above
+copyright notice, this list of conditions and the following disclaimer
+in the documentation and/or other materials provided with the
+distribution.
+   * Neither the name of Google Inc. nor the names of its
+contributors may be used to endorse or promote products derived from
+this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
diff --git a/pkg/sync/README.md b/pkg/sync/README.md
new file mode 100644
index 000000000..2183c4e20
--- /dev/null
+++ b/pkg/sync/README.md
@@ -0,0 +1,5 @@
+# Syncutil
+
+This package provides additional synchronization primitives not provided by the
+Go stdlib 'sync' package. It is partially derived from the upstream 'sync'
+package from go1.10.
diff --git a/pkg/sync/aliases.go b/pkg/sync/aliases.go
new file mode 100644
index 000000000..20c7ca041
--- /dev/null
+++ b/pkg/sync/aliases.go
@@ -0,0 +1,37 @@
+// Copyright 2020 The gVisor Authors.
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package sync
+
+import (
+	"sync"
+)
+
+// Aliases of standard library types.
+type (
+	// Mutex is an alias of sync.Mutex.
+	Mutex = sync.Mutex
+
+	// RWMutex is an alias of sync.RWMutex.
+	RWMutex = sync.RWMutex
+
+	// Cond is an alias of sync.Cond.
+	Cond = sync.Cond
+
+	// Locker is an alias of sync.Locker.
+	Locker = sync.Locker
+
+	// Once is an alias of sync.Once.
+	Once = sync.Once
+
+	// Pool is an alias of sync.Pool.
+	Pool = sync.Pool
+
+	// WaitGroup is an alias of sync.WaitGroup.
+	WaitGroup = sync.WaitGroup
+
+	// Map is an alias of sync.Map.
+	Map = sync.Map
+)
diff --git a/pkg/sync/atomicptr_unsafe.go b/pkg/sync/atomicptr_unsafe.go
new file mode 100644
index 000000000..525c4beed
--- /dev/null
+++ b/pkg/sync/atomicptr_unsafe.go
@@ -0,0 +1,47 @@
+// Copyright 2019 The gVisor Authors.
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package template doesn't exist. This file must be instantiated using the
+// go_template_instance rule in tools/go_generics/defs.bzl.
+package template
+
+import (
+	"sync/atomic"
+	"unsafe"
+)
+
+// Value is a required type parameter.
+type Value struct{}
+
+// An AtomicPtr is a pointer to a value of type Value that can be atomically
+// loaded and stored. The zero value of an AtomicPtr represents nil.
+//
+// Note that copying AtomicPtr by value performs a non-atomic read of the
+// stored pointer, which is unsafe if Store() can be called concurrently; in
+// this case, do `dst.Store(src.Load())` instead.
+//
+// +stateify savable
+type AtomicPtr struct {
+	ptr unsafe.Pointer `state:".(*Value)"`
+}
+
+func (p *AtomicPtr) savePtr() *Value {
+	return p.Load()
+}
+
+func (p *AtomicPtr) loadPtr(v *Value) {
+	p.Store(v)
+}
+
+// Load returns the value set by the most recent Store. It returns nil if there
+// has been no previous call to Store.
+func (p *AtomicPtr) Load() *Value {
+	return (*Value)(atomic.LoadPointer(&p.ptr))
+}
+
+// Store sets the value returned by Load to x.
+func (p *AtomicPtr) Store(x *Value) {
+	atomic.StorePointer(&p.ptr, (unsafe.Pointer)(x))
+}
diff --git a/pkg/sync/atomicptrtest/BUILD b/pkg/sync/atomicptrtest/BUILD
new file mode 100644
index 000000000..418eda29c
--- /dev/null
+++ b/pkg/sync/atomicptrtest/BUILD
@@ -0,0 +1,29 @@
+load("//tools/go_stateify:defs.bzl", "go_library")
+load("@io_bazel_rules_go//go:def.bzl", "go_test")
+load("//tools/go_generics:defs.bzl", "go_template_instance")
+
+package(licenses = ["notice"])
+
+go_template_instance(
+    name = "atomicptr_int",
+    out = "atomicptr_int_unsafe.go",
+    package = "atomicptr",
+    suffix = "Int",
+    template = "//pkg/sync:generic_atomicptr",
+    types = {
+        "Value": "int",
+    },
+)
+
+go_library(
+    name = "atomicptr",
+    srcs = ["atomicptr_int_unsafe.go"],
+    importpath = "gvisor.dev/gvisor/pkg/sync/atomicptr",
+)
+
+go_test(
+    name = "atomicptr_test",
+    size = "small",
+    srcs = ["atomicptr_test.go"],
+    embed = [":atomicptr"],
+)
diff --git a/pkg/sync/atomicptrtest/atomicptr_test.go b/pkg/sync/atomicptrtest/atomicptr_test.go
new file mode 100644
index 000000000..8fdc5112e
--- /dev/null
+++ b/pkg/sync/atomicptrtest/atomicptr_test.go
@@ -0,0 +1,31 @@
+// Copyright 2019 The gVisor Authors.
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package atomicptr
+
+import (
+	"testing"
+)
+
+func newInt(val int) *int {
+	return &val
+}
+
+func TestAtomicPtr(t *testing.T) {
+	var p AtomicPtrInt
+	if got := p.Load(); got != nil {
+		t.Errorf("initial value is %p (%v), wanted nil", got, got)
+	}
+	want := newInt(42)
+	p.Store(want)
+	if got := p.Load(); got != want {
+		t.Errorf("wrong value: got %p (%v), wanted %p (%v)", got, got, want, want)
+	}
+	want = newInt(100)
+	p.Store(want)
+	if got := p.Load(); got != want {
+		t.Errorf("wrong value: got %p (%v), wanted %p (%v)", got, got, want, want)
+	}
+}
diff --git a/pkg/sync/downgradable_rwmutex_test.go b/pkg/sync/downgradable_rwmutex_test.go
new file mode 100644
index 000000000..f04496bc5
--- /dev/null
+++ b/pkg/sync/downgradable_rwmutex_test.go
@@ -0,0 +1,150 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Copyright 2019 The gVisor Authors.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// GOMAXPROCS=10 go test
+
+// Copy/pasted from the standard library's sync/rwmutex_test.go, except for the
+// addition of downgradingWriter and the renaming of num_iterations to
+// numIterations to shut up Golint.
+
+package sync
+
+import (
+	"fmt"
+	"runtime"
+	"sync/atomic"
+	"testing"
+)
+
+func parallelReader(m *DowngradableRWMutex, clocked, cunlock, cdone chan bool) {
+	m.RLock()
+	clocked <- true
+	<-cunlock
+	m.RUnlock()
+	cdone <- true
+}
+
+func doTestParallelReaders(numReaders, gomaxprocs int) {
+	runtime.GOMAXPROCS(gomaxprocs)
+	var m DowngradableRWMutex
+	clocked := make(chan bool)
+	cunlock := make(chan bool)
+	cdone := make(chan bool)
+	for i := 0; i < numReaders; i++ {
+		go parallelReader(&m, clocked, cunlock, cdone)
+	}
+	// Wait for all parallel RLock()s to succeed.
+	for i := 0; i < numReaders; i++ {
+		<-clocked
+	}
+	for i := 0; i < numReaders; i++ {
+		cunlock <- true
+	}
+	// Wait for the goroutines to finish.
+	for i := 0; i < numReaders; i++ {
+		<-cdone
+	}
+}
+
+func TestParallelReaders(t *testing.T) {
+	defer runtime.GOMAXPROCS(runtime.GOMAXPROCS(-1))
+	doTestParallelReaders(1, 4)
+	doTestParallelReaders(3, 4)
+	doTestParallelReaders(4, 2)
+}
+
+func reader(rwm *DowngradableRWMutex, numIterations int, activity *int32, cdone chan bool) {
+	for i := 0; i < numIterations; i++ {
+		rwm.RLock()
+		n := atomic.AddInt32(activity, 1)
+		if n < 1 || n >= 10000 {
+			panic(fmt.Sprintf("wlock(%d)\n", n))
+		}
+		for i := 0; i < 100; i++ {
+		}
+		atomic.AddInt32(activity, -1)
+		rwm.RUnlock()
+	}
+	cdone <- true
+}
+
+func writer(rwm *DowngradableRWMutex, numIterations int, activity *int32, cdone chan bool) {
+	for i := 0; i < numIterations; i++ {
+		rwm.Lock()
+		n := atomic.AddInt32(activity, 10000)
+		if n != 10000 {
+			panic(fmt.Sprintf("wlock(%d)\n", n))
+		}
+		for i := 0; i < 100; i++ {
+		}
+		atomic.AddInt32(activity, -10000)
+		rwm.Unlock()
+	}
+	cdone <- true
+}
+
+func downgradingWriter(rwm *DowngradableRWMutex, numIterations int, activity *int32, cdone chan bool) {
+	for i := 0; i < numIterations; i++ {
+		rwm.Lock()
+		n := atomic.AddInt32(activity, 10000)
+		if n != 10000 {
+			panic(fmt.Sprintf("wlock(%d)\n", n))
+		}
+		for i := 0; i < 100; i++ {
+		}
+		atomic.AddInt32(activity, -10000)
+		rwm.DowngradeLock()
+		n = atomic.AddInt32(activity, 1)
+		if n < 1 || n >= 10000 {
+			panic(fmt.Sprintf("wlock(%d)\n", n))
+		}
+		for i := 0; i < 100; i++ {
+		}
+		n = atomic.AddInt32(activity, -1)
+		rwm.RUnlock()
+	}
+	cdone <- true
+}
+
+func HammerDowngradableRWMutex(gomaxprocs, numReaders, numIterations int) {
+	runtime.GOMAXPROCS(gomaxprocs)
+	// Number of active readers + 10000 * number of active writers.
+	var activity int32
+	var rwm DowngradableRWMutex
+	cdone := make(chan bool)
+	go writer(&rwm, numIterations, &activity, cdone)
+	go downgradingWriter(&rwm, numIterations, &activity, cdone)
+	var i int
+	for i = 0; i < numReaders/2; i++ {
+		go reader(&rwm, numIterations, &activity, cdone)
+	}
+	go writer(&rwm, numIterations, &activity, cdone)
+	go downgradingWriter(&rwm, numIterations, &activity, cdone)
+	for ; i < numReaders; i++ {
+		go reader(&rwm, numIterations, &activity, cdone)
+	}
+	// Wait for the 4 writers and all readers to finish.
+	for i := 0; i < 4+numReaders; i++ {
+		<-cdone
+	}
+}
+
+func TestDowngradableRWMutex(t *testing.T) {
+	defer runtime.GOMAXPROCS(runtime.GOMAXPROCS(-1))
+	n := 1000
+	if testing.Short() {
+		n = 5
+	}
+	HammerDowngradableRWMutex(1, 1, n)
+	HammerDowngradableRWMutex(1, 3, n)
+	HammerDowngradableRWMutex(1, 10, n)
+	HammerDowngradableRWMutex(4, 1, n)
+	HammerDowngradableRWMutex(4, 3, n)
+	HammerDowngradableRWMutex(4, 10, n)
+	HammerDowngradableRWMutex(10, 1, n)
+	HammerDowngradableRWMutex(10, 3, n)
+	HammerDowngradableRWMutex(10, 10, n)
+	HammerDowngradableRWMutex(10, 5, n)
+}
diff --git a/pkg/sync/downgradable_rwmutex_unsafe.go b/pkg/sync/downgradable_rwmutex_unsafe.go
new file mode 100644
index 000000000..9bb55cd3a
--- /dev/null
+++ b/pkg/sync/downgradable_rwmutex_unsafe.go
@@ -0,0 +1,146 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Copyright 2019 The gVisor Authors.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build go1.13
+// +build !go1.15
+
+// Check go:linkname function signatures when updating Go version.
+
+// This is mostly copied from the standard library's sync/rwmutex.go.
+//
+// Happens-before relationships indicated to the race detector:
+// - Unlock -> Lock (via writerSem)
+// - Unlock -> RLock (via readerSem)
+// - RUnlock -> Lock (via writerSem)
+// - DowngradeLock -> RLock (via readerSem)
+
+package sync
+
+import (
+	"sync"
+	"sync/atomic"
+	"unsafe"
+)
+
+//go:linkname runtimeSemacquire sync.runtime_Semacquire
+func runtimeSemacquire(s *uint32)
+
+//go:linkname runtimeSemrelease sync.runtime_Semrelease
+func runtimeSemrelease(s *uint32, handoff bool, skipframes int)
+
+// DowngradableRWMutex is identical to sync.RWMutex, but adds the DowngradeLock
+// method.
+type DowngradableRWMutex struct {
+	w           sync.Mutex // held if there are pending writers
+	writerSem   uint32     // semaphore for writers to wait for completing readers
+	readerSem   uint32     // semaphore for readers to wait for completing writers
+	readerCount int32      // number of pending readers
+	readerWait  int32      // number of departing readers
+}
+
+const rwmutexMaxReaders = 1 << 30
+
+// RLock locks rw for reading.
+func (rw *DowngradableRWMutex) RLock() {
+	if RaceEnabled {
+		RaceDisable()
+	}
+	if atomic.AddInt32(&rw.readerCount, 1) < 0 {
+		// A writer is pending, wait for it.
+		runtimeSemacquire(&rw.readerSem)
+	}
+	if RaceEnabled {
+		RaceEnable()
+		RaceAcquire(unsafe.Pointer(&rw.readerSem))
+	}
+}
+
+// RUnlock undoes a single RLock call.
+func (rw *DowngradableRWMutex) RUnlock() {
+	if RaceEnabled {
+		RaceReleaseMerge(unsafe.Pointer(&rw.writerSem))
+		RaceDisable()
+	}
+	if r := atomic.AddInt32(&rw.readerCount, -1); r < 0 {
+		if r+1 == 0 || r+1 == -rwmutexMaxReaders {
+			panic("RUnlock of unlocked DowngradableRWMutex")
+		}
+		// A writer is pending.
+		if atomic.AddInt32(&rw.readerWait, -1) == 0 {
+			// The last reader unblocks the writer.
+			runtimeSemrelease(&rw.writerSem, false, 0)
+		}
+	}
+	if RaceEnabled {
+		RaceEnable()
+	}
+}
+
+// Lock locks rw for writing.
+func (rw *DowngradableRWMutex) Lock() {
+	if RaceEnabled {
+		RaceDisable()
+	}
+	// First, resolve competition with other writers.
+	rw.w.Lock()
+	// Announce to readers there is a pending writer.
+	r := atomic.AddInt32(&rw.readerCount, -rwmutexMaxReaders) + rwmutexMaxReaders
+	// Wait for active readers.
+	if r != 0 && atomic.AddInt32(&rw.readerWait, r) != 0 {
+		runtimeSemacquire(&rw.writerSem)
+	}
+	if RaceEnabled {
+		RaceEnable()
+		RaceAcquire(unsafe.Pointer(&rw.writerSem))
+	}
+}
+
+// Unlock unlocks rw for writing.
+func (rw *DowngradableRWMutex) Unlock() {
+	if RaceEnabled {
+		RaceRelease(unsafe.Pointer(&rw.writerSem))
+		RaceRelease(unsafe.Pointer(&rw.readerSem))
+		RaceDisable()
+	}
+	// Announce to readers there is no active writer.
+	r := atomic.AddInt32(&rw.readerCount, rwmutexMaxReaders)
+	if r >= rwmutexMaxReaders {
+		panic("Unlock of unlocked DowngradableRWMutex")
+	}
+	// Unblock blocked readers, if any.
+	for i := 0; i < int(r); i++ {
+		runtimeSemrelease(&rw.readerSem, false, 0)
+	}
+	// Allow other writers to proceed.
+	rw.w.Unlock()
+	if RaceEnabled {
+		RaceEnable()
+	}
+}
+
+// DowngradeLock atomically unlocks rw for writing and locks it for reading.
+func (rw *DowngradableRWMutex) DowngradeLock() {
+	if RaceEnabled {
+		RaceRelease(unsafe.Pointer(&rw.readerSem))
+		RaceDisable()
+	}
+	// Announce to readers there is no active writer and one additional reader.
+	r := atomic.AddInt32(&rw.readerCount, rwmutexMaxReaders+1)
+	if r >= rwmutexMaxReaders+1 {
+		panic("DowngradeLock of unlocked DowngradableRWMutex")
+	}
+	// Unblock blocked readers, if any. Note that this loop starts as 1 since r
+	// includes this goroutine.
+	for i := 1; i < int(r); i++ {
+		runtimeSemrelease(&rw.readerSem, false, 0)
+	}
+	// Allow other writers to proceed to rw.w.Lock(). Note that they will still
+	// block on rw.writerSem since at least this reader exists, such that
+	// DowngradeLock() is atomic with the previous write lock.
+	rw.w.Unlock()
+	if RaceEnabled {
+		RaceEnable()
+	}
+}
diff --git a/pkg/sync/memmove_unsafe.go b/pkg/sync/memmove_unsafe.go
new file mode 100644
index 000000000..ad4a3a37e
--- /dev/null
+++ b/pkg/sync/memmove_unsafe.go
@@ -0,0 +1,28 @@
+// Copyright 2019 The gVisor Authors.
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build go1.12
+// +build !go1.15
+
+// Check go:linkname function signatures when updating Go version.
+
+package sync
+
+import (
+	"unsafe"
+)
+
+//go:linkname memmove runtime.memmove
+//go:noescape
+func memmove(to, from unsafe.Pointer, n uintptr)
+
+// Memmove is exported for SeqAtomicLoad/SeqAtomicTryLoad<T>, which can't
+// define it because go_generics can't update the go:linkname annotation.
+// Furthermore, go:linkname silently doesn't work if the local name is exported
+// (this is of course undocumented), which is why this indirection is
+// necessary.
+func Memmove(to, from unsafe.Pointer, n uintptr) {
+	memmove(to, from, n)
+}
diff --git a/pkg/sync/norace_unsafe.go b/pkg/sync/norace_unsafe.go
new file mode 100644
index 000000000..006055dd6
--- /dev/null
+++ b/pkg/sync/norace_unsafe.go
@@ -0,0 +1,35 @@
+// Copyright 2019 The gVisor Authors.
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build !race
+
+package sync
+
+import (
+	"unsafe"
+)
+
+// RaceEnabled is true if the Go data race detector is enabled.
+const RaceEnabled = false
+
+// RaceDisable has the same semantics as runtime.RaceDisable.
+func RaceDisable() {
+}
+
+// RaceEnable has the same semantics as runtime.RaceEnable.
+func RaceEnable() {
+}
+
+// RaceAcquire has the same semantics as runtime.RaceAcquire.
+func RaceAcquire(addr unsafe.Pointer) {
+}
+
+// RaceRelease has the same semantics as runtime.RaceRelease.
+func RaceRelease(addr unsafe.Pointer) {
+}
+
+// RaceReleaseMerge has the same semantics as runtime.RaceReleaseMerge.
+func RaceReleaseMerge(addr unsafe.Pointer) {
+}
diff --git a/pkg/sync/race_unsafe.go b/pkg/sync/race_unsafe.go
new file mode 100644
index 000000000..31d8fa9a6
--- /dev/null
+++ b/pkg/sync/race_unsafe.go
@@ -0,0 +1,41 @@
+// Copyright 2019 The gVisor Authors.
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build race
+
+package sync
+
+import (
+	"runtime"
+	"unsafe"
+)
+
+// RaceEnabled is true if the Go data race detector is enabled.
+const RaceEnabled = true
+
+// RaceDisable has the same semantics as runtime.RaceDisable.
+func RaceDisable() {
+	runtime.RaceDisable()
+}
+
+// RaceEnable has the same semantics as runtime.RaceEnable.
+func RaceEnable() {
+	runtime.RaceEnable()
+}
+
+// RaceAcquire has the same semantics as runtime.RaceAcquire.
+func RaceAcquire(addr unsafe.Pointer) {
+	runtime.RaceAcquire(addr)
+}
+
+// RaceRelease has the same semantics as runtime.RaceRelease.
+func RaceRelease(addr unsafe.Pointer) {
+	runtime.RaceRelease(addr)
+}
+
+// RaceReleaseMerge has the same semantics as runtime.RaceReleaseMerge.
+func RaceReleaseMerge(addr unsafe.Pointer) {
+	runtime.RaceReleaseMerge(addr)
+}
diff --git a/pkg/sync/seqatomic_unsafe.go b/pkg/sync/seqatomic_unsafe.go
new file mode 100644
index 000000000..eda6fb131
--- /dev/null
+++ b/pkg/sync/seqatomic_unsafe.go
@@ -0,0 +1,72 @@
+// Copyright 2019 The gVisor Authors.
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package template doesn't exist. This file must be instantiated using the
+// go_template_instance rule in tools/go_generics/defs.bzl.
+package template
+
+import (
+	"fmt"
+	"reflect"
+	"strings"
+	"unsafe"
+
+	"gvisor.dev/gvisor/pkg/sync"
+)
+
+// Value is a required type parameter.
+//
+// Value must not contain any pointers, including interface objects, function
+// objects, slices, maps, channels, unsafe.Pointer, and arrays or structs
+// containing any of the above. An init() function will panic if this property
+// does not hold.
+type Value struct{}
+
+// SeqAtomicLoad returns a copy of *ptr, ensuring that the read does not race
+// with any writer critical sections in sc.
+func SeqAtomicLoad(sc *sync.SeqCount, ptr *Value) Value {
+	// This function doesn't use SeqAtomicTryLoad because doing so is
+	// measurably, significantly (~20%) slower; Go is awful at inlining.
+	var val Value
+	for {
+		epoch := sc.BeginRead()
+		if sync.RaceEnabled {
+			// runtime.RaceDisable() doesn't actually stop the race detector,
+			// so it can't help us here. Instead, call runtime.memmove
+			// directly, which is not instrumented by the race detector.
+			sync.Memmove(unsafe.Pointer(&val), unsafe.Pointer(ptr), unsafe.Sizeof(val))
+		} else {
+			// This is ~40% faster for short reads than going through memmove.
+			val = *ptr
+		}
+		if sc.ReadOk(epoch) {
+			break
+		}
+	}
+	return val
+}
+
+// SeqAtomicTryLoad returns a copy of *ptr while in a reader critical section
+// in sc initiated by a call to sc.BeginRead() that returned epoch. If the read
+// would race with a writer critical section, SeqAtomicTryLoad returns
+// (unspecified, false).
+func SeqAtomicTryLoad(sc *sync.SeqCount, epoch sync.SeqCountEpoch, ptr *Value) (Value, bool) {
+	var val Value
+	if sync.RaceEnabled {
+		sync.Memmove(unsafe.Pointer(&val), unsafe.Pointer(ptr), unsafe.Sizeof(val))
+	} else {
+		val = *ptr
+	}
+	return val, sc.ReadOk(epoch)
+}
+
+func init() {
+	var val Value
+	typ := reflect.TypeOf(val)
+	name := typ.Name()
+	if ptrs := sync.PointersInType(typ, name); len(ptrs) != 0 {
+		panic(fmt.Sprintf("SeqAtomicLoad<%s> is invalid since values %s of type %s contain pointers:\n%s", typ, name, typ, strings.Join(ptrs, "\n")))
+	}
+}
diff --git a/pkg/sync/seqatomictest/BUILD b/pkg/sync/seqatomictest/BUILD
new file mode 100644
index 000000000..eba21518d
--- /dev/null
+++ b/pkg/sync/seqatomictest/BUILD
@@ -0,0 +1,33 @@
+load("//tools/go_stateify:defs.bzl", "go_library")
+load("@io_bazel_rules_go//go:def.bzl", "go_test")
+load("//tools/go_generics:defs.bzl", "go_template_instance")
+
+package(licenses = ["notice"])
+
+go_template_instance(
+    name = "seqatomic_int",
+    out = "seqatomic_int_unsafe.go",
+    package = "seqatomic",
+    suffix = "Int",
+    template = "//pkg/sync:generic_seqatomic",
+    types = {
+        "Value": "int",
+    },
+)
+
+go_library(
+    name = "seqatomic",
+    srcs = ["seqatomic_int_unsafe.go"],
+    importpath = "gvisor.dev/gvisor/pkg/sync/seqatomic",
+    deps = [
+        "//pkg/sync",
+    ],
+)
+
+go_test(
+    name = "seqatomic_test",
+    size = "small",
+    srcs = ["seqatomic_test.go"],
+    embed = [":seqatomic"],
+    deps = ["//pkg/sync"],
+)
diff --git a/pkg/sync/seqatomictest/seqatomic_test.go b/pkg/sync/seqatomictest/seqatomic_test.go
new file mode 100644
index 000000000..2c4568b07
--- /dev/null
+++ b/pkg/sync/seqatomictest/seqatomic_test.go
@@ -0,0 +1,132 @@
+// Copyright 2018 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package seqatomic
+
+import (
+	"sync/atomic"
+	"testing"
+	"time"
+
+	"gvisor.dev/gvisor/pkg/sync"
+)
+
+func TestSeqAtomicLoadUncontended(t *testing.T) {
+	var seq sync.SeqCount
+	const want = 1
+	data := want
+	if got := SeqAtomicLoadInt(&seq, &data); got != want {
+		t.Errorf("SeqAtomicLoadInt: got %v, wanted %v", got, want)
+	}
+}
+
+func TestSeqAtomicLoadAfterWrite(t *testing.T) {
+	var seq sync.SeqCount
+	var data int
+	const want = 1
+	seq.BeginWrite()
+	data = want
+	seq.EndWrite()
+	if got := SeqAtomicLoadInt(&seq, &data); got != want {
+		t.Errorf("SeqAtomicLoadInt: got %v, wanted %v", got, want)
+	}
+}
+
+func TestSeqAtomicLoadDuringWrite(t *testing.T) {
+	var seq sync.SeqCount
+	var data int
+	const want = 1
+	seq.BeginWrite()
+	go func() {
+		time.Sleep(time.Second)
+		data = want
+		seq.EndWrite()
+	}()
+	if got := SeqAtomicLoadInt(&seq, &data); got != want {
+		t.Errorf("SeqAtomicLoadInt: got %v, wanted %v", got, want)
+	}
+}
+
+func TestSeqAtomicTryLoadUncontended(t *testing.T) {
+	var seq sync.SeqCount
+	const want = 1
+	data := want
+	epoch := seq.BeginRead()
+	if got, ok := SeqAtomicTryLoadInt(&seq, epoch, &data); !ok || got != want {
+		t.Errorf("SeqAtomicTryLoadInt: got (%v, %v), wanted (%v, true)", got, ok, want)
+	}
+}
+
+func TestSeqAtomicTryLoadDuringWrite(t *testing.T) {
+	var seq sync.SeqCount
+	var data int
+	epoch := seq.BeginRead()
+	seq.BeginWrite()
+	if got, ok := SeqAtomicTryLoadInt(&seq, epoch, &data); ok {
+		t.Errorf("SeqAtomicTryLoadInt: got (%v, true), wanted (_, false)", got)
+	}
+	seq.EndWrite()
+}
+
+func TestSeqAtomicTryLoadAfterWrite(t *testing.T) {
+	var seq sync.SeqCount
+	var data int
+	epoch := seq.BeginRead()
+	seq.BeginWrite()
+	seq.EndWrite()
+	if got, ok := SeqAtomicTryLoadInt(&seq, epoch, &data); ok {
+		t.Errorf("SeqAtomicTryLoadInt: got (%v, true), wanted (_, false)", got)
+	}
+}
+
+func BenchmarkSeqAtomicLoadIntUncontended(b *testing.B) {
+	var seq sync.SeqCount
+	const want = 42
+	data := want
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			if got := SeqAtomicLoadInt(&seq, &data); got != want {
+				b.Fatalf("SeqAtomicLoadInt: got %v, wanted %v", got, want)
+			}
+		}
+	})
+}
+
+func BenchmarkSeqAtomicTryLoadIntUncontended(b *testing.B) {
+	var seq sync.SeqCount
+	const want = 42
+	data := want
+	b.RunParallel(func(pb *testing.PB) {
+		epoch := seq.BeginRead()
+		for pb.Next() {
+			if got, ok := SeqAtomicTryLoadInt(&seq, epoch, &data); !ok || got != want {
+				b.Fatalf("SeqAtomicTryLoadInt: got (%v, %v), wanted (%v, true)", got, ok, want)
+			}
+		}
+	})
+}
+
+// For comparison:
+func BenchmarkAtomicValueLoadIntUncontended(b *testing.B) {
+	var a atomic.Value
+	const want = 42
+	a.Store(int(want))
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			if got := a.Load().(int); got != want {
+				b.Fatalf("atomic.Value.Load: got %v, wanted %v", got, want)
+			}
+		}
+	})
+}
diff --git a/pkg/sync/seqcount.go b/pkg/sync/seqcount.go
new file mode 100644
index 000000000..a1e895352
--- /dev/null
+++ b/pkg/sync/seqcount.go
@@ -0,0 +1,149 @@
+// Copyright 2019 The gVisor Authors.
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package sync
+
+import (
+	"fmt"
+	"reflect"
+	"runtime"
+	"sync/atomic"
+)
+
+// SeqCount is a synchronization primitive for optimistic reader/writer
+// synchronization in cases where readers can work with stale data and
+// therefore do not need to block writers.
+//
+// Compared to sync/atomic.Value:
+//
+// - Mutation of SeqCount-protected data does not require memory allocation,
+// whereas atomic.Value generally does. This is a significant advantage when
+// writes are common.
+//
+// - Atomic reads of SeqCount-protected data require copying. This is a
+// disadvantage when atomic reads are common.
+//
+// - SeqCount may be more flexible: correct use of SeqCount.ReadOk allows other
+// operations to be made atomic with reads of SeqCount-protected data.
+//
+// - SeqCount may be less flexible: as of this writing, SeqCount-protected data
+// cannot include pointers.
+//
+// - SeqCount is more cumbersome to use; atomic reads of SeqCount-protected
+// data require instantiating function templates using go_generics (see
+// seqatomic.go).
+type SeqCount struct {
+	// epoch is incremented by BeginWrite and EndWrite, such that epoch is odd
+	// if a writer critical section is active, and a read from data protected
+	// by this SeqCount is atomic iff epoch is the same even value before and
+	// after the read.
+	epoch uint32
+}
+
+// SeqCountEpoch tracks writer critical sections in a SeqCount.
+type SeqCountEpoch struct {
+	val uint32
+}
+
+// We assume that:
+//
+// - All functions in sync/atomic that perform a memory read are at least a
+// read fence: memory reads before calls to such functions cannot be reordered
+// after the call, and memory reads after calls to such functions cannot be
+// reordered before the call, even if those reads do not use sync/atomic.
+//
+// - All functions in sync/atomic that perform a memory write are at least a
+// write fence: memory writes before calls to such functions cannot be
+// reordered after the call, and memory writes after calls to such functions
+// cannot be reordered before the call, even if those writes do not use
+// sync/atomic.
+//
+// As of this writing, the Go memory model completely fails to describe
+// sync/atomic, but these properties are implied by
+// https://groups.google.com/forum/#!topic/golang-nuts/7EnEhM3U7B8.
+
+// BeginRead indicates the beginning of a reader critical section. Reader
+// critical sections DO NOT BLOCK writer critical sections, so operations in a
+// reader critical section MAY RACE with writer critical sections. Races are
+// detected by ReadOk at the end of the reader critical section. Thus, the
+// low-level structure of readers is generally:
+//
+//     for {
+//         epoch := seq.BeginRead()
+//         // do something idempotent with seq-protected data
+//         if seq.ReadOk(epoch) {
+//             break
+//         }
+//     }
+//
+// However, since reader critical sections may race with writer critical
+// sections, the Go race detector will (accurately) flag data races in readers
+// using this pattern. Most users of SeqCount will need to use the
+// SeqAtomicLoad function template in seqatomic.go.
+func (s *SeqCount) BeginRead() SeqCountEpoch {
+	epoch := atomic.LoadUint32(&s.epoch)
+	for epoch&1 != 0 {
+		runtime.Gosched()
+		epoch = atomic.LoadUint32(&s.epoch)
+	}
+	return SeqCountEpoch{epoch}
+}
+
+// ReadOk returns true if the reader critical section initiated by a previous
+// call to BeginRead() that returned epoch did not race with any writer critical
+// sections.
+//
+// ReadOk may be called any number of times during a reader critical section.
+// Reader critical sections do not need to be explicitly terminated; the last
+// call to ReadOk is implicitly the end of the reader critical section.
+func (s *SeqCount) ReadOk(epoch SeqCountEpoch) bool {
+	return atomic.LoadUint32(&s.epoch) == epoch.val
+}
+
+// BeginWrite indicates the beginning of a writer critical section.
+//
+// SeqCount does not support concurrent writer critical sections; clients with
+// concurrent writers must synchronize them using e.g. sync.Mutex.
+func (s *SeqCount) BeginWrite() {
+	if epoch := atomic.AddUint32(&s.epoch, 1); epoch&1 == 0 {
+		panic("SeqCount.BeginWrite during writer critical section")
+	}
+}
+
+// EndWrite ends the effect of a preceding BeginWrite.
+func (s *SeqCount) EndWrite() {
+	if epoch := atomic.AddUint32(&s.epoch, 1); epoch&1 != 0 {
+		panic("SeqCount.EndWrite outside writer critical section")
+	}
+}
+
+// PointersInType returns a list of pointers reachable from values named
+// valName of the given type.
+//
+// PointersInType is not exhaustive, but it is guaranteed that if typ contains
+// at least one pointer, then PointersInTypeOf returns a non-empty list.
+func PointersInType(typ reflect.Type, valName string) []string {
+	switch kind := typ.Kind(); kind {
+	case reflect.Bool, reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64, reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr, reflect.Float32, reflect.Float64, reflect.Complex64, reflect.Complex128:
+		return nil
+
+	case reflect.Chan, reflect.Func, reflect.Interface, reflect.Map, reflect.Ptr, reflect.Slice, reflect.String, reflect.UnsafePointer:
+		return []string{valName}
+
+	case reflect.Array:
+		return PointersInType(typ.Elem(), valName+"[]")
+
+	case reflect.Struct:
+		var ptrs []string
+		for i, n := 0, typ.NumField(); i < n; i++ {
+			field := typ.Field(i)
+			ptrs = append(ptrs, PointersInType(field.Type, fmt.Sprintf("%s.%s", valName, field.Name))...)
+		}
+		return ptrs
+
+	default:
+		return []string{fmt.Sprintf("%s (of type %s with unknown kind %s)", valName, typ, kind)}
+	}
+}
diff --git a/pkg/sync/seqcount_test.go b/pkg/sync/seqcount_test.go
new file mode 100644
index 000000000..6eb7b4b59
--- /dev/null
+++ b/pkg/sync/seqcount_test.go
@@ -0,0 +1,153 @@
+// Copyright 2019 The gVisor Authors.
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package sync
+
+import (
+	"reflect"
+	"testing"
+	"time"
+)
+
+func TestSeqCountWriteUncontended(t *testing.T) {
+	var seq SeqCount
+	seq.BeginWrite()
+	seq.EndWrite()
+}
+
+func TestSeqCountReadUncontended(t *testing.T) {
+	var seq SeqCount
+	epoch := seq.BeginRead()
+	if !seq.ReadOk(epoch) {
+		t.Errorf("ReadOk: got false, wanted true")
+	}
+}
+
+func TestSeqCountBeginReadAfterWrite(t *testing.T) {
+	var seq SeqCount
+	var data int32
+	const want = 1
+	seq.BeginWrite()
+	data = want
+	seq.EndWrite()
+	epoch := seq.BeginRead()
+	if data != want {
+		t.Errorf("Reader: got %v, wanted %v", data, want)
+	}
+	if !seq.ReadOk(epoch) {
+		t.Errorf("ReadOk: got false, wanted true")
+	}
+}
+
+func TestSeqCountBeginReadDuringWrite(t *testing.T) {
+	var seq SeqCount
+	var data int
+	const want = 1
+	seq.BeginWrite()
+	go func() {
+		time.Sleep(time.Second)
+		data = want
+		seq.EndWrite()
+	}()
+	epoch := seq.BeginRead()
+	if data != want {
+		t.Errorf("Reader: got %v, wanted %v", data, want)
+	}
+	if !seq.ReadOk(epoch) {
+		t.Errorf("ReadOk: got false, wanted true")
+	}
+}
+
+func TestSeqCountReadOkAfterWrite(t *testing.T) {
+	var seq SeqCount
+	epoch := seq.BeginRead()
+	seq.BeginWrite()
+	seq.EndWrite()
+	if seq.ReadOk(epoch) {
+		t.Errorf("ReadOk: got true, wanted false")
+	}
+}
+
+func TestSeqCountReadOkDuringWrite(t *testing.T) {
+	var seq SeqCount
+	epoch := seq.BeginRead()
+	seq.BeginWrite()
+	if seq.ReadOk(epoch) {
+		t.Errorf("ReadOk: got true, wanted false")
+	}
+	seq.EndWrite()
+}
+
+func BenchmarkSeqCountWriteUncontended(b *testing.B) {
+	var seq SeqCount
+	for i := 0; i < b.N; i++ {
+		seq.BeginWrite()
+		seq.EndWrite()
+	}
+}
+
+func BenchmarkSeqCountReadUncontended(b *testing.B) {
+	var seq SeqCount
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			epoch := seq.BeginRead()
+			if !seq.ReadOk(epoch) {
+				b.Fatalf("ReadOk: got false, wanted true")
+			}
+		}
+	})
+}
+
+func TestPointersInType(t *testing.T) {
+	for _, test := range []struct {
+		name string // used for both test and value name
+		val  interface{}
+		ptrs []string
+	}{
+		{
+			name: "EmptyStruct",
+			val:  struct{}{},
+		},
+		{
+			name: "Int",
+			val:  int(0),
+		},
+		{
+			name: "MixedStruct",
+			val: struct {
+				b             bool
+				I             int
+				ExportedPtr   *struct{}
+				unexportedPtr *struct{}
+				arr           [2]int
+				ptrArr        [2]*int
+				nestedStruct  struct {
+					nestedNonptr int
+					nestedPtr    *int
+				}
+				structArr [1]struct {
+					nonptr int
+					ptr    *int
+				}
+			}{},
+			ptrs: []string{
+				"MixedStruct.ExportedPtr",
+				"MixedStruct.unexportedPtr",
+				"MixedStruct.ptrArr[]",
+				"MixedStruct.nestedStruct.nestedPtr",
+				"MixedStruct.structArr[].ptr",
+			},
+		},
+	} {
+		t.Run(test.name, func(t *testing.T) {
+			typ := reflect.TypeOf(test.val)
+			ptrs := PointersInType(typ, test.name)
+			t.Logf("Found pointers: %v", ptrs)
+			if (len(ptrs) != 0 || len(test.ptrs) != 0) && !reflect.DeepEqual(ptrs, test.ptrs) {
+				t.Errorf("Got %v, wanted %v", ptrs, test.ptrs)
+			}
+		})
+	}
+}
diff --git a/pkg/sync/syncutil.go b/pkg/sync/syncutil.go
new file mode 100644
index 000000000..b16cf5333
--- /dev/null
+++ b/pkg/sync/syncutil.go
@@ -0,0 +1,7 @@
+// Copyright 2019 The gVisor Authors.
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package sync provides synchronization primitives.
+package sync
diff --git a/pkg/syncutil/BUILD b/pkg/syncutil/BUILD
deleted file mode 100644
index cb1f41628..000000000
--- a/pkg/syncutil/BUILD
+++ /dev/null
@@ -1,52 +0,0 @@
-load("//tools/go_stateify:defs.bzl", "go_library")
-load("@io_bazel_rules_go//go:def.bzl", "go_test")
-load("//tools/go_generics:defs.bzl", "go_template")
-
-package(
-    default_visibility = ["//:sandbox"],
-    licenses = ["notice"],
-)
-
-exports_files(["LICENSE"])
-
-go_template(
-    name = "generic_atomicptr",
-    srcs = ["atomicptr_unsafe.go"],
-    types = [
-        "Value",
-    ],
-)
-
-go_template(
-    name = "generic_seqatomic",
-    srcs = ["seqatomic_unsafe.go"],
-    types = [
-        "Value",
-    ],
-    deps = [
-        ":sync",
-    ],
-)
-
-go_library(
-    name = "syncutil",
-    srcs = [
-        "downgradable_rwmutex_unsafe.go",
-        "memmove_unsafe.go",
-        "norace_unsafe.go",
-        "race_unsafe.go",
-        "seqcount.go",
-        "syncutil.go",
-    ],
-    importpath = "gvisor.dev/gvisor/pkg/syncutil",
-)
-
-go_test(
-    name = "syncutil_test",
-    size = "small",
-    srcs = [
-        "downgradable_rwmutex_test.go",
-        "seqcount_test.go",
-    ],
-    embed = [":syncutil"],
-)
diff --git a/pkg/syncutil/LICENSE b/pkg/syncutil/LICENSE
deleted file mode 100644
index 6a66aea5e..000000000
--- a/pkg/syncutil/LICENSE
+++ /dev/null
@@ -1,27 +0,0 @@
-Copyright (c) 2009 The Go Authors. All rights reserved.
-
-Redistribution and use in source and binary forms, with or without
-modification, are permitted provided that the following conditions are
-met:
-
-   * Redistributions of source code must retain the above copyright
-notice, this list of conditions and the following disclaimer.
-   * Redistributions in binary form must reproduce the above
-copyright notice, this list of conditions and the following disclaimer
-in the documentation and/or other materials provided with the
-distribution.
-   * Neither the name of Google Inc. nor the names of its
-contributors may be used to endorse or promote products derived from
-this software without specific prior written permission.
-
-THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
-"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
-LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
-A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
-OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
-SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
-LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
-DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
-THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
-(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
-OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
diff --git a/pkg/syncutil/README.md b/pkg/syncutil/README.md
deleted file mode 100644
index 2183c4e20..000000000
--- a/pkg/syncutil/README.md
+++ /dev/null
@@ -1,5 +0,0 @@
-# Syncutil
-
-This package provides additional synchronization primitives not provided by the
-Go stdlib 'sync' package. It is partially derived from the upstream 'sync'
-package from go1.10.
diff --git a/pkg/syncutil/atomicptr_unsafe.go b/pkg/syncutil/atomicptr_unsafe.go
deleted file mode 100644
index 525c4beed..000000000
--- a/pkg/syncutil/atomicptr_unsafe.go
+++ /dev/null
@@ -1,47 +0,0 @@
-// Copyright 2019 The gVisor Authors.
-//
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-// Package template doesn't exist. This file must be instantiated using the
-// go_template_instance rule in tools/go_generics/defs.bzl.
-package template
-
-import (
-	"sync/atomic"
-	"unsafe"
-)
-
-// Value is a required type parameter.
-type Value struct{}
-
-// An AtomicPtr is a pointer to a value of type Value that can be atomically
-// loaded and stored. The zero value of an AtomicPtr represents nil.
-//
-// Note that copying AtomicPtr by value performs a non-atomic read of the
-// stored pointer, which is unsafe if Store() can be called concurrently; in
-// this case, do `dst.Store(src.Load())` instead.
-//
-// +stateify savable
-type AtomicPtr struct {
-	ptr unsafe.Pointer `state:".(*Value)"`
-}
-
-func (p *AtomicPtr) savePtr() *Value {
-	return p.Load()
-}
-
-func (p *AtomicPtr) loadPtr(v *Value) {
-	p.Store(v)
-}
-
-// Load returns the value set by the most recent Store. It returns nil if there
-// has been no previous call to Store.
-func (p *AtomicPtr) Load() *Value {
-	return (*Value)(atomic.LoadPointer(&p.ptr))
-}
-
-// Store sets the value returned by Load to x.
-func (p *AtomicPtr) Store(x *Value) {
-	atomic.StorePointer(&p.ptr, (unsafe.Pointer)(x))
-}
diff --git a/pkg/syncutil/atomicptrtest/BUILD b/pkg/syncutil/atomicptrtest/BUILD
deleted file mode 100644
index 63f411a90..000000000
--- a/pkg/syncutil/atomicptrtest/BUILD
+++ /dev/null
@@ -1,29 +0,0 @@
-load("//tools/go_stateify:defs.bzl", "go_library")
-load("@io_bazel_rules_go//go:def.bzl", "go_test")
-load("//tools/go_generics:defs.bzl", "go_template_instance")
-
-package(licenses = ["notice"])
-
-go_template_instance(
-    name = "atomicptr_int",
-    out = "atomicptr_int_unsafe.go",
-    package = "atomicptr",
-    suffix = "Int",
-    template = "//pkg/syncutil:generic_atomicptr",
-    types = {
-        "Value": "int",
-    },
-)
-
-go_library(
-    name = "atomicptr",
-    srcs = ["atomicptr_int_unsafe.go"],
-    importpath = "gvisor.dev/gvisor/pkg/syncutil/atomicptr",
-)
-
-go_test(
-    name = "atomicptr_test",
-    size = "small",
-    srcs = ["atomicptr_test.go"],
-    embed = [":atomicptr"],
-)
diff --git a/pkg/syncutil/atomicptrtest/atomicptr_test.go b/pkg/syncutil/atomicptrtest/atomicptr_test.go
deleted file mode 100644
index 8fdc5112e..000000000
--- a/pkg/syncutil/atomicptrtest/atomicptr_test.go
+++ /dev/null
@@ -1,31 +0,0 @@
-// Copyright 2019 The gVisor Authors.
-//
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package atomicptr
-
-import (
-	"testing"
-)
-
-func newInt(val int) *int {
-	return &val
-}
-
-func TestAtomicPtr(t *testing.T) {
-	var p AtomicPtrInt
-	if got := p.Load(); got != nil {
-		t.Errorf("initial value is %p (%v), wanted nil", got, got)
-	}
-	want := newInt(42)
-	p.Store(want)
-	if got := p.Load(); got != want {
-		t.Errorf("wrong value: got %p (%v), wanted %p (%v)", got, got, want, want)
-	}
-	want = newInt(100)
-	p.Store(want)
-	if got := p.Load(); got != want {
-		t.Errorf("wrong value: got %p (%v), wanted %p (%v)", got, got, want, want)
-	}
-}
diff --git a/pkg/syncutil/downgradable_rwmutex_test.go b/pkg/syncutil/downgradable_rwmutex_test.go
deleted file mode 100644
index ffaf7ecc7..000000000
--- a/pkg/syncutil/downgradable_rwmutex_test.go
+++ /dev/null
@@ -1,150 +0,0 @@
-// Copyright 2009 The Go Authors. All rights reserved.
-// Copyright 2019 The gVisor Authors.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-// GOMAXPROCS=10 go test
-
-// Copy/pasted from the standard library's sync/rwmutex_test.go, except for the
-// addition of downgradingWriter and the renaming of num_iterations to
-// numIterations to shut up Golint.
-
-package syncutil
-
-import (
-	"fmt"
-	"runtime"
-	"sync/atomic"
-	"testing"
-)
-
-func parallelReader(m *DowngradableRWMutex, clocked, cunlock, cdone chan bool) {
-	m.RLock()
-	clocked <- true
-	<-cunlock
-	m.RUnlock()
-	cdone <- true
-}
-
-func doTestParallelReaders(numReaders, gomaxprocs int) {
-	runtime.GOMAXPROCS(gomaxprocs)
-	var m DowngradableRWMutex
-	clocked := make(chan bool)
-	cunlock := make(chan bool)
-	cdone := make(chan bool)
-	for i := 0; i < numReaders; i++ {
-		go parallelReader(&m, clocked, cunlock, cdone)
-	}
-	// Wait for all parallel RLock()s to succeed.
-	for i := 0; i < numReaders; i++ {
-		<-clocked
-	}
-	for i := 0; i < numReaders; i++ {
-		cunlock <- true
-	}
-	// Wait for the goroutines to finish.
-	for i := 0; i < numReaders; i++ {
-		<-cdone
-	}
-}
-
-func TestParallelReaders(t *testing.T) {
-	defer runtime.GOMAXPROCS(runtime.GOMAXPROCS(-1))
-	doTestParallelReaders(1, 4)
-	doTestParallelReaders(3, 4)
-	doTestParallelReaders(4, 2)
-}
-
-func reader(rwm *DowngradableRWMutex, numIterations int, activity *int32, cdone chan bool) {
-	for i := 0; i < numIterations; i++ {
-		rwm.RLock()
-		n := atomic.AddInt32(activity, 1)
-		if n < 1 || n >= 10000 {
-			panic(fmt.Sprintf("wlock(%d)\n", n))
-		}
-		for i := 0; i < 100; i++ {
-		}
-		atomic.AddInt32(activity, -1)
-		rwm.RUnlock()
-	}
-	cdone <- true
-}
-
-func writer(rwm *DowngradableRWMutex, numIterations int, activity *int32, cdone chan bool) {
-	for i := 0; i < numIterations; i++ {
-		rwm.Lock()
-		n := atomic.AddInt32(activity, 10000)
-		if n != 10000 {
-			panic(fmt.Sprintf("wlock(%d)\n", n))
-		}
-		for i := 0; i < 100; i++ {
-		}
-		atomic.AddInt32(activity, -10000)
-		rwm.Unlock()
-	}
-	cdone <- true
-}
-
-func downgradingWriter(rwm *DowngradableRWMutex, numIterations int, activity *int32, cdone chan bool) {
-	for i := 0; i < numIterations; i++ {
-		rwm.Lock()
-		n := atomic.AddInt32(activity, 10000)
-		if n != 10000 {
-			panic(fmt.Sprintf("wlock(%d)\n", n))
-		}
-		for i := 0; i < 100; i++ {
-		}
-		atomic.AddInt32(activity, -10000)
-		rwm.DowngradeLock()
-		n = atomic.AddInt32(activity, 1)
-		if n < 1 || n >= 10000 {
-			panic(fmt.Sprintf("wlock(%d)\n", n))
-		}
-		for i := 0; i < 100; i++ {
-		}
-		n = atomic.AddInt32(activity, -1)
-		rwm.RUnlock()
-	}
-	cdone <- true
-}
-
-func HammerDowngradableRWMutex(gomaxprocs, numReaders, numIterations int) {
-	runtime.GOMAXPROCS(gomaxprocs)
-	// Number of active readers + 10000 * number of active writers.
-	var activity int32
-	var rwm DowngradableRWMutex
-	cdone := make(chan bool)
-	go writer(&rwm, numIterations, &activity, cdone)
-	go downgradingWriter(&rwm, numIterations, &activity, cdone)
-	var i int
-	for i = 0; i < numReaders/2; i++ {
-		go reader(&rwm, numIterations, &activity, cdone)
-	}
-	go writer(&rwm, numIterations, &activity, cdone)
-	go downgradingWriter(&rwm, numIterations, &activity, cdone)
-	for ; i < numReaders; i++ {
-		go reader(&rwm, numIterations, &activity, cdone)
-	}
-	// Wait for the 4 writers and all readers to finish.
-	for i := 0; i < 4+numReaders; i++ {
-		<-cdone
-	}
-}
-
-func TestDowngradableRWMutex(t *testing.T) {
-	defer runtime.GOMAXPROCS(runtime.GOMAXPROCS(-1))
-	n := 1000
-	if testing.Short() {
-		n = 5
-	}
-	HammerDowngradableRWMutex(1, 1, n)
-	HammerDowngradableRWMutex(1, 3, n)
-	HammerDowngradableRWMutex(1, 10, n)
-	HammerDowngradableRWMutex(4, 1, n)
-	HammerDowngradableRWMutex(4, 3, n)
-	HammerDowngradableRWMutex(4, 10, n)
-	HammerDowngradableRWMutex(10, 1, n)
-	HammerDowngradableRWMutex(10, 3, n)
-	HammerDowngradableRWMutex(10, 10, n)
-	HammerDowngradableRWMutex(10, 5, n)
-}
diff --git a/pkg/syncutil/downgradable_rwmutex_unsafe.go b/pkg/syncutil/downgradable_rwmutex_unsafe.go
deleted file mode 100644
index 51e11555d..000000000
--- a/pkg/syncutil/downgradable_rwmutex_unsafe.go
+++ /dev/null
@@ -1,146 +0,0 @@
-// Copyright 2009 The Go Authors. All rights reserved.
-// Copyright 2019 The gVisor Authors.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-// +build go1.13
-// +build !go1.15
-
-// Check go:linkname function signatures when updating Go version.
-
-// This is mostly copied from the standard library's sync/rwmutex.go.
-//
-// Happens-before relationships indicated to the race detector:
-// - Unlock -> Lock (via writerSem)
-// - Unlock -> RLock (via readerSem)
-// - RUnlock -> Lock (via writerSem)
-// - DowngradeLock -> RLock (via readerSem)
-
-package syncutil
-
-import (
-	"sync"
-	"sync/atomic"
-	"unsafe"
-)
-
-//go:linkname runtimeSemacquire sync.runtime_Semacquire
-func runtimeSemacquire(s *uint32)
-
-//go:linkname runtimeSemrelease sync.runtime_Semrelease
-func runtimeSemrelease(s *uint32, handoff bool, skipframes int)
-
-// DowngradableRWMutex is identical to sync.RWMutex, but adds the DowngradeLock
-// method.
-type DowngradableRWMutex struct {
-	w           sync.Mutex // held if there are pending writers
-	writerSem   uint32     // semaphore for writers to wait for completing readers
-	readerSem   uint32     // semaphore for readers to wait for completing writers
-	readerCount int32      // number of pending readers
-	readerWait  int32      // number of departing readers
-}
-
-const rwmutexMaxReaders = 1 << 30
-
-// RLock locks rw for reading.
-func (rw *DowngradableRWMutex) RLock() {
-	if RaceEnabled {
-		RaceDisable()
-	}
-	if atomic.AddInt32(&rw.readerCount, 1) < 0 {
-		// A writer is pending, wait for it.
-		runtimeSemacquire(&rw.readerSem)
-	}
-	if RaceEnabled {
-		RaceEnable()
-		RaceAcquire(unsafe.Pointer(&rw.readerSem))
-	}
-}
-
-// RUnlock undoes a single RLock call.
-func (rw *DowngradableRWMutex) RUnlock() {
-	if RaceEnabled {
-		RaceReleaseMerge(unsafe.Pointer(&rw.writerSem))
-		RaceDisable()
-	}
-	if r := atomic.AddInt32(&rw.readerCount, -1); r < 0 {
-		if r+1 == 0 || r+1 == -rwmutexMaxReaders {
-			panic("RUnlock of unlocked DowngradableRWMutex")
-		}
-		// A writer is pending.
-		if atomic.AddInt32(&rw.readerWait, -1) == 0 {
-			// The last reader unblocks the writer.
-			runtimeSemrelease(&rw.writerSem, false, 0)
-		}
-	}
-	if RaceEnabled {
-		RaceEnable()
-	}
-}
-
-// Lock locks rw for writing.
-func (rw *DowngradableRWMutex) Lock() {
-	if RaceEnabled {
-		RaceDisable()
-	}
-	// First, resolve competition with other writers.
-	rw.w.Lock()
-	// Announce to readers there is a pending writer.
-	r := atomic.AddInt32(&rw.readerCount, -rwmutexMaxReaders) + rwmutexMaxReaders
-	// Wait for active readers.
-	if r != 0 && atomic.AddInt32(&rw.readerWait, r) != 0 {
-		runtimeSemacquire(&rw.writerSem)
-	}
-	if RaceEnabled {
-		RaceEnable()
-		RaceAcquire(unsafe.Pointer(&rw.writerSem))
-	}
-}
-
-// Unlock unlocks rw for writing.
-func (rw *DowngradableRWMutex) Unlock() {
-	if RaceEnabled {
-		RaceRelease(unsafe.Pointer(&rw.writerSem))
-		RaceRelease(unsafe.Pointer(&rw.readerSem))
-		RaceDisable()
-	}
-	// Announce to readers there is no active writer.
-	r := atomic.AddInt32(&rw.readerCount, rwmutexMaxReaders)
-	if r >= rwmutexMaxReaders {
-		panic("Unlock of unlocked DowngradableRWMutex")
-	}
-	// Unblock blocked readers, if any.
-	for i := 0; i < int(r); i++ {
-		runtimeSemrelease(&rw.readerSem, false, 0)
-	}
-	// Allow other writers to proceed.
-	rw.w.Unlock()
-	if RaceEnabled {
-		RaceEnable()
-	}
-}
-
-// DowngradeLock atomically unlocks rw for writing and locks it for reading.
-func (rw *DowngradableRWMutex) DowngradeLock() {
-	if RaceEnabled {
-		RaceRelease(unsafe.Pointer(&rw.readerSem))
-		RaceDisable()
-	}
-	// Announce to readers there is no active writer and one additional reader.
-	r := atomic.AddInt32(&rw.readerCount, rwmutexMaxReaders+1)
-	if r >= rwmutexMaxReaders+1 {
-		panic("DowngradeLock of unlocked DowngradableRWMutex")
-	}
-	// Unblock blocked readers, if any. Note that this loop starts as 1 since r
-	// includes this goroutine.
-	for i := 1; i < int(r); i++ {
-		runtimeSemrelease(&rw.readerSem, false, 0)
-	}
-	// Allow other writers to proceed to rw.w.Lock(). Note that they will still
-	// block on rw.writerSem since at least this reader exists, such that
-	// DowngradeLock() is atomic with the previous write lock.
-	rw.w.Unlock()
-	if RaceEnabled {
-		RaceEnable()
-	}
-}
diff --git a/pkg/syncutil/memmove_unsafe.go b/pkg/syncutil/memmove_unsafe.go
deleted file mode 100644
index 348675baa..000000000
--- a/pkg/syncutil/memmove_unsafe.go
+++ /dev/null
@@ -1,28 +0,0 @@
-// Copyright 2019 The gVisor Authors.
-//
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-// +build go1.12
-// +build !go1.15
-
-// Check go:linkname function signatures when updating Go version.
-
-package syncutil
-
-import (
-	"unsafe"
-)
-
-//go:linkname memmove runtime.memmove
-//go:noescape
-func memmove(to, from unsafe.Pointer, n uintptr)
-
-// Memmove is exported for SeqAtomicLoad/SeqAtomicTryLoad<T>, which can't
-// define it because go_generics can't update the go:linkname annotation.
-// Furthermore, go:linkname silently doesn't work if the local name is exported
-// (this is of course undocumented), which is why this indirection is
-// necessary.
-func Memmove(to, from unsafe.Pointer, n uintptr) {
-	memmove(to, from, n)
-}
diff --git a/pkg/syncutil/norace_unsafe.go b/pkg/syncutil/norace_unsafe.go
deleted file mode 100644
index 0a0a9deda..000000000
--- a/pkg/syncutil/norace_unsafe.go
+++ /dev/null
@@ -1,35 +0,0 @@
-// Copyright 2019 The gVisor Authors.
-//
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-// +build !race
-
-package syncutil
-
-import (
-	"unsafe"
-)
-
-// RaceEnabled is true if the Go data race detector is enabled.
-const RaceEnabled = false
-
-// RaceDisable has the same semantics as runtime.RaceDisable.
-func RaceDisable() {
-}
-
-// RaceEnable has the same semantics as runtime.RaceEnable.
-func RaceEnable() {
-}
-
-// RaceAcquire has the same semantics as runtime.RaceAcquire.
-func RaceAcquire(addr unsafe.Pointer) {
-}
-
-// RaceRelease has the same semantics as runtime.RaceRelease.
-func RaceRelease(addr unsafe.Pointer) {
-}
-
-// RaceReleaseMerge has the same semantics as runtime.RaceReleaseMerge.
-func RaceReleaseMerge(addr unsafe.Pointer) {
-}
diff --git a/pkg/syncutil/race_unsafe.go b/pkg/syncutil/race_unsafe.go
deleted file mode 100644
index 206067ec1..000000000
--- a/pkg/syncutil/race_unsafe.go
+++ /dev/null
@@ -1,41 +0,0 @@
-// Copyright 2019 The gVisor Authors.
-//
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-// +build race
-
-package syncutil
-
-import (
-	"runtime"
-	"unsafe"
-)
-
-// RaceEnabled is true if the Go data race detector is enabled.
-const RaceEnabled = true
-
-// RaceDisable has the same semantics as runtime.RaceDisable.
-func RaceDisable() {
-	runtime.RaceDisable()
-}
-
-// RaceEnable has the same semantics as runtime.RaceEnable.
-func RaceEnable() {
-	runtime.RaceEnable()
-}
-
-// RaceAcquire has the same semantics as runtime.RaceAcquire.
-func RaceAcquire(addr unsafe.Pointer) {
-	runtime.RaceAcquire(addr)
-}
-
-// RaceRelease has the same semantics as runtime.RaceRelease.
-func RaceRelease(addr unsafe.Pointer) {
-	runtime.RaceRelease(addr)
-}
-
-// RaceReleaseMerge has the same semantics as runtime.RaceReleaseMerge.
-func RaceReleaseMerge(addr unsafe.Pointer) {
-	runtime.RaceReleaseMerge(addr)
-}
diff --git a/pkg/syncutil/seqatomic_unsafe.go b/pkg/syncutil/seqatomic_unsafe.go
deleted file mode 100644
index cb6d2eb22..000000000
--- a/pkg/syncutil/seqatomic_unsafe.go
+++ /dev/null
@@ -1,72 +0,0 @@
-// Copyright 2019 The gVisor Authors.
-//
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-// Package template doesn't exist. This file must be instantiated using the
-// go_template_instance rule in tools/go_generics/defs.bzl.
-package template
-
-import (
-	"fmt"
-	"reflect"
-	"strings"
-	"unsafe"
-
-	"gvisor.dev/gvisor/pkg/syncutil"
-)
-
-// Value is a required type parameter.
-//
-// Value must not contain any pointers, including interface objects, function
-// objects, slices, maps, channels, unsafe.Pointer, and arrays or structs
-// containing any of the above. An init() function will panic if this property
-// does not hold.
-type Value struct{}
-
-// SeqAtomicLoad returns a copy of *ptr, ensuring that the read does not race
-// with any writer critical sections in sc.
-func SeqAtomicLoad(sc *syncutil.SeqCount, ptr *Value) Value {
-	// This function doesn't use SeqAtomicTryLoad because doing so is
-	// measurably, significantly (~20%) slower; Go is awful at inlining.
-	var val Value
-	for {
-		epoch := sc.BeginRead()
-		if syncutil.RaceEnabled {
-			// runtime.RaceDisable() doesn't actually stop the race detector,
-			// so it can't help us here. Instead, call runtime.memmove
-			// directly, which is not instrumented by the race detector.
-			syncutil.Memmove(unsafe.Pointer(&val), unsafe.Pointer(ptr), unsafe.Sizeof(val))
-		} else {
-			// This is ~40% faster for short reads than going through memmove.
-			val = *ptr
-		}
-		if sc.ReadOk(epoch) {
-			break
-		}
-	}
-	return val
-}
-
-// SeqAtomicTryLoad returns a copy of *ptr while in a reader critical section
-// in sc initiated by a call to sc.BeginRead() that returned epoch. If the read
-// would race with a writer critical section, SeqAtomicTryLoad returns
-// (unspecified, false).
-func SeqAtomicTryLoad(sc *syncutil.SeqCount, epoch syncutil.SeqCountEpoch, ptr *Value) (Value, bool) {
-	var val Value
-	if syncutil.RaceEnabled {
-		syncutil.Memmove(unsafe.Pointer(&val), unsafe.Pointer(ptr), unsafe.Sizeof(val))
-	} else {
-		val = *ptr
-	}
-	return val, sc.ReadOk(epoch)
-}
-
-func init() {
-	var val Value
-	typ := reflect.TypeOf(val)
-	name := typ.Name()
-	if ptrs := syncutil.PointersInType(typ, name); len(ptrs) != 0 {
-		panic(fmt.Sprintf("SeqAtomicLoad<%s> is invalid since values %s of type %s contain pointers:\n%s", typ, name, typ, strings.Join(ptrs, "\n")))
-	}
-}
diff --git a/pkg/syncutil/seqatomictest/BUILD b/pkg/syncutil/seqatomictest/BUILD
deleted file mode 100644
index ba18f3238..000000000
--- a/pkg/syncutil/seqatomictest/BUILD
+++ /dev/null
@@ -1,35 +0,0 @@
-load("//tools/go_stateify:defs.bzl", "go_library")
-load("@io_bazel_rules_go//go:def.bzl", "go_test")
-load("//tools/go_generics:defs.bzl", "go_template_instance")
-
-package(licenses = ["notice"])
-
-go_template_instance(
-    name = "seqatomic_int",
-    out = "seqatomic_int_unsafe.go",
-    package = "seqatomic",
-    suffix = "Int",
-    template = "//pkg/syncutil:generic_seqatomic",
-    types = {
-        "Value": "int",
-    },
-)
-
-go_library(
-    name = "seqatomic",
-    srcs = ["seqatomic_int_unsafe.go"],
-    importpath = "gvisor.dev/gvisor/pkg/syncutil/seqatomic",
-    deps = [
-        "//pkg/syncutil",
-    ],
-)
-
-go_test(
-    name = "seqatomic_test",
-    size = "small",
-    srcs = ["seqatomic_test.go"],
-    embed = [":seqatomic"],
-    deps = [
-        "//pkg/syncutil",
-    ],
-)
diff --git a/pkg/syncutil/seqatomictest/seqatomic_test.go b/pkg/syncutil/seqatomictest/seqatomic_test.go
deleted file mode 100644
index b0db44999..000000000
--- a/pkg/syncutil/seqatomictest/seqatomic_test.go
+++ /dev/null
@@ -1,132 +0,0 @@
-// Copyright 2018 The gVisor Authors.
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//     http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-package seqatomic
-
-import (
-	"sync/atomic"
-	"testing"
-	"time"
-
-	"gvisor.dev/gvisor/pkg/syncutil"
-)
-
-func TestSeqAtomicLoadUncontended(t *testing.T) {
-	var seq syncutil.SeqCount
-	const want = 1
-	data := want
-	if got := SeqAtomicLoadInt(&seq, &data); got != want {
-		t.Errorf("SeqAtomicLoadInt: got %v, wanted %v", got, want)
-	}
-}
-
-func TestSeqAtomicLoadAfterWrite(t *testing.T) {
-	var seq syncutil.SeqCount
-	var data int
-	const want = 1
-	seq.BeginWrite()
-	data = want
-	seq.EndWrite()
-	if got := SeqAtomicLoadInt(&seq, &data); got != want {
-		t.Errorf("SeqAtomicLoadInt: got %v, wanted %v", got, want)
-	}
-}
-
-func TestSeqAtomicLoadDuringWrite(t *testing.T) {
-	var seq syncutil.SeqCount
-	var data int
-	const want = 1
-	seq.BeginWrite()
-	go func() {
-		time.Sleep(time.Second)
-		data = want
-		seq.EndWrite()
-	}()
-	if got := SeqAtomicLoadInt(&seq, &data); got != want {
-		t.Errorf("SeqAtomicLoadInt: got %v, wanted %v", got, want)
-	}
-}
-
-func TestSeqAtomicTryLoadUncontended(t *testing.T) {
-	var seq syncutil.SeqCount
-	const want = 1
-	data := want
-	epoch := seq.BeginRead()
-	if got, ok := SeqAtomicTryLoadInt(&seq, epoch, &data); !ok || got != want {
-		t.Errorf("SeqAtomicTryLoadInt: got (%v, %v), wanted (%v, true)", got, ok, want)
-	}
-}
-
-func TestSeqAtomicTryLoadDuringWrite(t *testing.T) {
-	var seq syncutil.SeqCount
-	var data int
-	epoch := seq.BeginRead()
-	seq.BeginWrite()
-	if got, ok := SeqAtomicTryLoadInt(&seq, epoch, &data); ok {
-		t.Errorf("SeqAtomicTryLoadInt: got (%v, true), wanted (_, false)", got)
-	}
-	seq.EndWrite()
-}
-
-func TestSeqAtomicTryLoadAfterWrite(t *testing.T) {
-	var seq syncutil.SeqCount
-	var data int
-	epoch := seq.BeginRead()
-	seq.BeginWrite()
-	seq.EndWrite()
-	if got, ok := SeqAtomicTryLoadInt(&seq, epoch, &data); ok {
-		t.Errorf("SeqAtomicTryLoadInt: got (%v, true), wanted (_, false)", got)
-	}
-}
-
-func BenchmarkSeqAtomicLoadIntUncontended(b *testing.B) {
-	var seq syncutil.SeqCount
-	const want = 42
-	data := want
-	b.RunParallel(func(pb *testing.PB) {
-		for pb.Next() {
-			if got := SeqAtomicLoadInt(&seq, &data); got != want {
-				b.Fatalf("SeqAtomicLoadInt: got %v, wanted %v", got, want)
-			}
-		}
-	})
-}
-
-func BenchmarkSeqAtomicTryLoadIntUncontended(b *testing.B) {
-	var seq syncutil.SeqCount
-	const want = 42
-	data := want
-	b.RunParallel(func(pb *testing.PB) {
-		epoch := seq.BeginRead()
-		for pb.Next() {
-			if got, ok := SeqAtomicTryLoadInt(&seq, epoch, &data); !ok || got != want {
-				b.Fatalf("SeqAtomicTryLoadInt: got (%v, %v), wanted (%v, true)", got, ok, want)
-			}
-		}
-	})
-}
-
-// For comparison:
-func BenchmarkAtomicValueLoadIntUncontended(b *testing.B) {
-	var a atomic.Value
-	const want = 42
-	a.Store(int(want))
-	b.RunParallel(func(pb *testing.PB) {
-		for pb.Next() {
-			if got := a.Load().(int); got != want {
-				b.Fatalf("atomic.Value.Load: got %v, wanted %v", got, want)
-			}
-		}
-	})
-}
diff --git a/pkg/syncutil/seqcount.go b/pkg/syncutil/seqcount.go
deleted file mode 100644
index 11d8dbfaa..000000000
--- a/pkg/syncutil/seqcount.go
+++ /dev/null
@@ -1,149 +0,0 @@
-// Copyright 2019 The gVisor Authors.
-//
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package syncutil
-
-import (
-	"fmt"
-	"reflect"
-	"runtime"
-	"sync/atomic"
-)
-
-// SeqCount is a synchronization primitive for optimistic reader/writer
-// synchronization in cases where readers can work with stale data and
-// therefore do not need to block writers.
-//
-// Compared to sync/atomic.Value:
-//
-// - Mutation of SeqCount-protected data does not require memory allocation,
-// whereas atomic.Value generally does. This is a significant advantage when
-// writes are common.
-//
-// - Atomic reads of SeqCount-protected data require copying. This is a
-// disadvantage when atomic reads are common.
-//
-// - SeqCount may be more flexible: correct use of SeqCount.ReadOk allows other
-// operations to be made atomic with reads of SeqCount-protected data.
-//
-// - SeqCount may be less flexible: as of this writing, SeqCount-protected data
-// cannot include pointers.
-//
-// - SeqCount is more cumbersome to use; atomic reads of SeqCount-protected
-// data require instantiating function templates using go_generics (see
-// seqatomic.go).
-type SeqCount struct {
-	// epoch is incremented by BeginWrite and EndWrite, such that epoch is odd
-	// if a writer critical section is active, and a read from data protected
-	// by this SeqCount is atomic iff epoch is the same even value before and
-	// after the read.
-	epoch uint32
-}
-
-// SeqCountEpoch tracks writer critical sections in a SeqCount.
-type SeqCountEpoch struct {
-	val uint32
-}
-
-// We assume that:
-//
-// - All functions in sync/atomic that perform a memory read are at least a
-// read fence: memory reads before calls to such functions cannot be reordered
-// after the call, and memory reads after calls to such functions cannot be
-// reordered before the call, even if those reads do not use sync/atomic.
-//
-// - All functions in sync/atomic that perform a memory write are at least a
-// write fence: memory writes before calls to such functions cannot be
-// reordered after the call, and memory writes after calls to such functions
-// cannot be reordered before the call, even if those writes do not use
-// sync/atomic.
-//
-// As of this writing, the Go memory model completely fails to describe
-// sync/atomic, but these properties are implied by
-// https://groups.google.com/forum/#!topic/golang-nuts/7EnEhM3U7B8.
-
-// BeginRead indicates the beginning of a reader critical section. Reader
-// critical sections DO NOT BLOCK writer critical sections, so operations in a
-// reader critical section MAY RACE with writer critical sections. Races are
-// detected by ReadOk at the end of the reader critical section. Thus, the
-// low-level structure of readers is generally:
-//
-//     for {
-//         epoch := seq.BeginRead()
-//         // do something idempotent with seq-protected data
-//         if seq.ReadOk(epoch) {
-//             break
-//         }
-//     }
-//
-// However, since reader critical sections may race with writer critical
-// sections, the Go race detector will (accurately) flag data races in readers
-// using this pattern. Most users of SeqCount will need to use the
-// SeqAtomicLoad function template in seqatomic.go.
-func (s *SeqCount) BeginRead() SeqCountEpoch {
-	epoch := atomic.LoadUint32(&s.epoch)
-	for epoch&1 != 0 {
-		runtime.Gosched()
-		epoch = atomic.LoadUint32(&s.epoch)
-	}
-	return SeqCountEpoch{epoch}
-}
-
-// ReadOk returns true if the reader critical section initiated by a previous
-// call to BeginRead() that returned epoch did not race with any writer critical
-// sections.
-//
-// ReadOk may be called any number of times during a reader critical section.
-// Reader critical sections do not need to be explicitly terminated; the last
-// call to ReadOk is implicitly the end of the reader critical section.
-func (s *SeqCount) ReadOk(epoch SeqCountEpoch) bool {
-	return atomic.LoadUint32(&s.epoch) == epoch.val
-}
-
-// BeginWrite indicates the beginning of a writer critical section.
-//
-// SeqCount does not support concurrent writer critical sections; clients with
-// concurrent writers must synchronize them using e.g. sync.Mutex.
-func (s *SeqCount) BeginWrite() {
-	if epoch := atomic.AddUint32(&s.epoch, 1); epoch&1 == 0 {
-		panic("SeqCount.BeginWrite during writer critical section")
-	}
-}
-
-// EndWrite ends the effect of a preceding BeginWrite.
-func (s *SeqCount) EndWrite() {
-	if epoch := atomic.AddUint32(&s.epoch, 1); epoch&1 != 0 {
-		panic("SeqCount.EndWrite outside writer critical section")
-	}
-}
-
-// PointersInType returns a list of pointers reachable from values named
-// valName of the given type.
-//
-// PointersInType is not exhaustive, but it is guaranteed that if typ contains
-// at least one pointer, then PointersInTypeOf returns a non-empty list.
-func PointersInType(typ reflect.Type, valName string) []string {
-	switch kind := typ.Kind(); kind {
-	case reflect.Bool, reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64, reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr, reflect.Float32, reflect.Float64, reflect.Complex64, reflect.Complex128:
-		return nil
-
-	case reflect.Chan, reflect.Func, reflect.Interface, reflect.Map, reflect.Ptr, reflect.Slice, reflect.String, reflect.UnsafePointer:
-		return []string{valName}
-
-	case reflect.Array:
-		return PointersInType(typ.Elem(), valName+"[]")
-
-	case reflect.Struct:
-		var ptrs []string
-		for i, n := 0, typ.NumField(); i < n; i++ {
-			field := typ.Field(i)
-			ptrs = append(ptrs, PointersInType(field.Type, fmt.Sprintf("%s.%s", valName, field.Name))...)
-		}
-		return ptrs
-
-	default:
-		return []string{fmt.Sprintf("%s (of type %s with unknown kind %s)", valName, typ, kind)}
-	}
-}
diff --git a/pkg/syncutil/seqcount_test.go b/pkg/syncutil/seqcount_test.go
deleted file mode 100644
index 14d6aedea..000000000
--- a/pkg/syncutil/seqcount_test.go
+++ /dev/null
@@ -1,153 +0,0 @@
-// Copyright 2019 The gVisor Authors.
-//
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package syncutil
-
-import (
-	"reflect"
-	"testing"
-	"time"
-)
-
-func TestSeqCountWriteUncontended(t *testing.T) {
-	var seq SeqCount
-	seq.BeginWrite()
-	seq.EndWrite()
-}
-
-func TestSeqCountReadUncontended(t *testing.T) {
-	var seq SeqCount
-	epoch := seq.BeginRead()
-	if !seq.ReadOk(epoch) {
-		t.Errorf("ReadOk: got false, wanted true")
-	}
-}
-
-func TestSeqCountBeginReadAfterWrite(t *testing.T) {
-	var seq SeqCount
-	var data int32
-	const want = 1
-	seq.BeginWrite()
-	data = want
-	seq.EndWrite()
-	epoch := seq.BeginRead()
-	if data != want {
-		t.Errorf("Reader: got %v, wanted %v", data, want)
-	}
-	if !seq.ReadOk(epoch) {
-		t.Errorf("ReadOk: got false, wanted true")
-	}
-}
-
-func TestSeqCountBeginReadDuringWrite(t *testing.T) {
-	var seq SeqCount
-	var data int
-	const want = 1
-	seq.BeginWrite()
-	go func() {
-		time.Sleep(time.Second)
-		data = want
-		seq.EndWrite()
-	}()
-	epoch := seq.BeginRead()
-	if data != want {
-		t.Errorf("Reader: got %v, wanted %v", data, want)
-	}
-	if !seq.ReadOk(epoch) {
-		t.Errorf("ReadOk: got false, wanted true")
-	}
-}
-
-func TestSeqCountReadOkAfterWrite(t *testing.T) {
-	var seq SeqCount
-	epoch := seq.BeginRead()
-	seq.BeginWrite()
-	seq.EndWrite()
-	if seq.ReadOk(epoch) {
-		t.Errorf("ReadOk: got true, wanted false")
-	}
-}
-
-func TestSeqCountReadOkDuringWrite(t *testing.T) {
-	var seq SeqCount
-	epoch := seq.BeginRead()
-	seq.BeginWrite()
-	if seq.ReadOk(epoch) {
-		t.Errorf("ReadOk: got true, wanted false")
-	}
-	seq.EndWrite()
-}
-
-func BenchmarkSeqCountWriteUncontended(b *testing.B) {
-	var seq SeqCount
-	for i := 0; i < b.N; i++ {
-		seq.BeginWrite()
-		seq.EndWrite()
-	}
-}
-
-func BenchmarkSeqCountReadUncontended(b *testing.B) {
-	var seq SeqCount
-	b.RunParallel(func(pb *testing.PB) {
-		for pb.Next() {
-			epoch := seq.BeginRead()
-			if !seq.ReadOk(epoch) {
-				b.Fatalf("ReadOk: got false, wanted true")
-			}
-		}
-	})
-}
-
-func TestPointersInType(t *testing.T) {
-	for _, test := range []struct {
-		name string // used for both test and value name
-		val  interface{}
-		ptrs []string
-	}{
-		{
-			name: "EmptyStruct",
-			val:  struct{}{},
-		},
-		{
-			name: "Int",
-			val:  int(0),
-		},
-		{
-			name: "MixedStruct",
-			val: struct {
-				b             bool
-				I             int
-				ExportedPtr   *struct{}
-				unexportedPtr *struct{}
-				arr           [2]int
-				ptrArr        [2]*int
-				nestedStruct  struct {
-					nestedNonptr int
-					nestedPtr    *int
-				}
-				structArr [1]struct {
-					nonptr int
-					ptr    *int
-				}
-			}{},
-			ptrs: []string{
-				"MixedStruct.ExportedPtr",
-				"MixedStruct.unexportedPtr",
-				"MixedStruct.ptrArr[]",
-				"MixedStruct.nestedStruct.nestedPtr",
-				"MixedStruct.structArr[].ptr",
-			},
-		},
-	} {
-		t.Run(test.name, func(t *testing.T) {
-			typ := reflect.TypeOf(test.val)
-			ptrs := PointersInType(typ, test.name)
-			t.Logf("Found pointers: %v", ptrs)
-			if (len(ptrs) != 0 || len(test.ptrs) != 0) && !reflect.DeepEqual(ptrs, test.ptrs) {
-				t.Errorf("Got %v, wanted %v", ptrs, test.ptrs)
-			}
-		})
-	}
-}
diff --git a/pkg/syncutil/syncutil.go b/pkg/syncutil/syncutil.go
deleted file mode 100644
index 66e750d06..000000000
--- a/pkg/syncutil/syncutil.go
+++ /dev/null
@@ -1,7 +0,0 @@
-// Copyright 2019 The gVisor Authors.
-//
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-// Package syncutil provides synchronization primitives.
-package syncutil
diff --git a/pkg/tcpip/BUILD b/pkg/tcpip/BUILD
index e07ebd153..db06d02c6 100644
--- a/pkg/tcpip/BUILD
+++ b/pkg/tcpip/BUILD
@@ -15,6 +15,7 @@ go_library(
     importpath = "gvisor.dev/gvisor/pkg/tcpip",
     visibility = ["//visibility:public"],
     deps = [
+        "//pkg/sync",
         "//pkg/tcpip/buffer",
         "//pkg/tcpip/iptables",
         "//pkg/waiter",
diff --git a/pkg/tcpip/adapters/gonet/BUILD b/pkg/tcpip/adapters/gonet/BUILD
index 78df5a0b1..3df7d18d3 100644
--- a/pkg/tcpip/adapters/gonet/BUILD
+++ b/pkg/tcpip/adapters/gonet/BUILD
@@ -9,6 +9,7 @@ go_library(
     importpath = "gvisor.dev/gvisor/pkg/tcpip/adapters/gonet",
     visibility = ["//visibility:public"],
     deps = [
+        "//pkg/sync",
         "//pkg/tcpip",
         "//pkg/tcpip/buffer",
         "//pkg/tcpip/stack",
diff --git a/pkg/tcpip/adapters/gonet/gonet.go b/pkg/tcpip/adapters/gonet/gonet.go
index cd6ce930a..a2f44b496 100644
--- a/pkg/tcpip/adapters/gonet/gonet.go
+++ b/pkg/tcpip/adapters/gonet/gonet.go
@@ -20,9 +20,9 @@ import (
 	"errors"
 	"io"
 	"net"
-	"sync"
 	"time"
 
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/tcpip"
 	"gvisor.dev/gvisor/pkg/tcpip/buffer"
 	"gvisor.dev/gvisor/pkg/tcpip/stack"
diff --git a/pkg/tcpip/link/fdbased/BUILD b/pkg/tcpip/link/fdbased/BUILD
index 897c94821..66cc53ed4 100644
--- a/pkg/tcpip/link/fdbased/BUILD
+++ b/pkg/tcpip/link/fdbased/BUILD
@@ -16,6 +16,7 @@ go_library(
     importpath = "gvisor.dev/gvisor/pkg/tcpip/link/fdbased",
     visibility = ["//visibility:public"],
     deps = [
+        "//pkg/sync",
         "//pkg/tcpip",
         "//pkg/tcpip/buffer",
         "//pkg/tcpip/header",
diff --git a/pkg/tcpip/link/fdbased/endpoint.go b/pkg/tcpip/link/fdbased/endpoint.go
index fa8a703d9..b7f60178e 100644
--- a/pkg/tcpip/link/fdbased/endpoint.go
+++ b/pkg/tcpip/link/fdbased/endpoint.go
@@ -41,10 +41,10 @@ package fdbased
 
 import (
 	"fmt"
-	"sync"
 	"syscall"
 
 	"golang.org/x/sys/unix"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/tcpip"
 	"gvisor.dev/gvisor/pkg/tcpip/buffer"
 	"gvisor.dev/gvisor/pkg/tcpip/header"
diff --git a/pkg/tcpip/link/sharedmem/BUILD b/pkg/tcpip/link/sharedmem/BUILD
index a4f9cdd69..09165dd4c 100644
--- a/pkg/tcpip/link/sharedmem/BUILD
+++ b/pkg/tcpip/link/sharedmem/BUILD
@@ -15,6 +15,7 @@ go_library(
     visibility = ["//visibility:public"],
     deps = [
         "//pkg/log",
+        "//pkg/sync",
         "//pkg/tcpip",
         "//pkg/tcpip/buffer",
         "//pkg/tcpip/header",
@@ -31,6 +32,7 @@ go_test(
     ],
     embed = [":sharedmem"],
     deps = [
+        "//pkg/sync",
         "//pkg/tcpip",
         "//pkg/tcpip/buffer",
         "//pkg/tcpip/header",
diff --git a/pkg/tcpip/link/sharedmem/pipe/BUILD b/pkg/tcpip/link/sharedmem/pipe/BUILD
index 6b5bc542c..a0d4ad0be 100644
--- a/pkg/tcpip/link/sharedmem/pipe/BUILD
+++ b/pkg/tcpip/link/sharedmem/pipe/BUILD
@@ -21,4 +21,5 @@ go_test(
         "pipe_test.go",
     ],
     embed = [":pipe"],
+    deps = ["//pkg/sync"],
 )
diff --git a/pkg/tcpip/link/sharedmem/pipe/pipe_test.go b/pkg/tcpip/link/sharedmem/pipe/pipe_test.go
index 59ef69a8b..dc239a0d0 100644
--- a/pkg/tcpip/link/sharedmem/pipe/pipe_test.go
+++ b/pkg/tcpip/link/sharedmem/pipe/pipe_test.go
@@ -18,8 +18,9 @@ import (
 	"math/rand"
 	"reflect"
 	"runtime"
-	"sync"
 	"testing"
+
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 func TestSimpleReadWrite(t *testing.T) {
diff --git a/pkg/tcpip/link/sharedmem/sharedmem.go b/pkg/tcpip/link/sharedmem/sharedmem.go
index 080f9d667..655e537c4 100644
--- a/pkg/tcpip/link/sharedmem/sharedmem.go
+++ b/pkg/tcpip/link/sharedmem/sharedmem.go
@@ -23,11 +23,11 @@
 package sharedmem
 
 import (
-	"sync"
 	"sync/atomic"
 	"syscall"
 
 	"gvisor.dev/gvisor/pkg/log"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/tcpip"
 	"gvisor.dev/gvisor/pkg/tcpip/buffer"
 	"gvisor.dev/gvisor/pkg/tcpip/header"
diff --git a/pkg/tcpip/link/sharedmem/sharedmem_test.go b/pkg/tcpip/link/sharedmem/sharedmem_test.go
index 89603c48f..5c729a439 100644
--- a/pkg/tcpip/link/sharedmem/sharedmem_test.go
+++ b/pkg/tcpip/link/sharedmem/sharedmem_test.go
@@ -22,11 +22,11 @@ import (
 	"math/rand"
 	"os"
 	"strings"
-	"sync"
 	"syscall"
 	"testing"
 	"time"
 
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/tcpip"
 	"gvisor.dev/gvisor/pkg/tcpip/buffer"
 	"gvisor.dev/gvisor/pkg/tcpip/header"
diff --git a/pkg/tcpip/network/fragmentation/BUILD b/pkg/tcpip/network/fragmentation/BUILD
index acf1e022c..ed16076fd 100644
--- a/pkg/tcpip/network/fragmentation/BUILD
+++ b/pkg/tcpip/network/fragmentation/BUILD
@@ -28,6 +28,7 @@ go_library(
     visibility = ["//visibility:public"],
     deps = [
         "//pkg/log",
+        "//pkg/sync",
         "//pkg/tcpip",
         "//pkg/tcpip/buffer",
     ],
diff --git a/pkg/tcpip/network/fragmentation/fragmentation.go b/pkg/tcpip/network/fragmentation/fragmentation.go
index 6da5238ec..92f2aa13a 100644
--- a/pkg/tcpip/network/fragmentation/fragmentation.go
+++ b/pkg/tcpip/network/fragmentation/fragmentation.go
@@ -19,9 +19,9 @@ package fragmentation
 import (
 	"fmt"
 	"log"
-	"sync"
 	"time"
 
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/tcpip/buffer"
 )
 
diff --git a/pkg/tcpip/network/fragmentation/reassembler.go b/pkg/tcpip/network/fragmentation/reassembler.go
index 9e002e396..0a83d81f2 100644
--- a/pkg/tcpip/network/fragmentation/reassembler.go
+++ b/pkg/tcpip/network/fragmentation/reassembler.go
@@ -18,9 +18,9 @@ import (
 	"container/heap"
 	"fmt"
 	"math"
-	"sync"
 	"time"
 
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/tcpip/buffer"
 )
 
diff --git a/pkg/tcpip/ports/BUILD b/pkg/tcpip/ports/BUILD
index e156b01f6..a6ef3bdcc 100644
--- a/pkg/tcpip/ports/BUILD
+++ b/pkg/tcpip/ports/BUILD
@@ -9,6 +9,7 @@ go_library(
     importpath = "gvisor.dev/gvisor/pkg/tcpip/ports",
     visibility = ["//visibility:public"],
     deps = [
+        "//pkg/sync",
         "//pkg/tcpip",
     ],
 )
diff --git a/pkg/tcpip/ports/ports.go b/pkg/tcpip/ports/ports.go
index 6c5e19e8f..b937cb84b 100644
--- a/pkg/tcpip/ports/ports.go
+++ b/pkg/tcpip/ports/ports.go
@@ -18,9 +18,9 @@ package ports
 import (
 	"math"
 	"math/rand"
-	"sync"
 	"sync/atomic"
 
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/tcpip"
 )
 
diff --git a/pkg/tcpip/stack/BUILD b/pkg/tcpip/stack/BUILD
index 826fca4de..6a8654105 100644
--- a/pkg/tcpip/stack/BUILD
+++ b/pkg/tcpip/stack/BUILD
@@ -36,6 +36,7 @@ go_library(
         "//pkg/ilist",
         "//pkg/rand",
         "//pkg/sleep",
+        "//pkg/sync",
         "//pkg/tcpip",
         "//pkg/tcpip/buffer",
         "//pkg/tcpip/hash/jenkins",
@@ -80,6 +81,7 @@ go_test(
     embed = [":stack"],
     deps = [
         "//pkg/sleep",
+        "//pkg/sync",
         "//pkg/tcpip",
     ],
 )
diff --git a/pkg/tcpip/stack/linkaddrcache.go b/pkg/tcpip/stack/linkaddrcache.go
index 267df60d1..403557fd7 100644
--- a/pkg/tcpip/stack/linkaddrcache.go
+++ b/pkg/tcpip/stack/linkaddrcache.go
@@ -16,10 +16,10 @@ package stack
 
 import (
 	"fmt"
-	"sync"
 	"time"
 
 	"gvisor.dev/gvisor/pkg/sleep"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/tcpip"
 )
 
diff --git a/pkg/tcpip/stack/linkaddrcache_test.go b/pkg/tcpip/stack/linkaddrcache_test.go
index 9946b8fe8..1baa498d0 100644
--- a/pkg/tcpip/stack/linkaddrcache_test.go
+++ b/pkg/tcpip/stack/linkaddrcache_test.go
@@ -16,12 +16,12 @@ package stack
 
 import (
 	"fmt"
-	"sync"
 	"sync/atomic"
 	"testing"
 	"time"
 
 	"gvisor.dev/gvisor/pkg/sleep"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/tcpip"
 )
 
diff --git a/pkg/tcpip/stack/nic.go b/pkg/tcpip/stack/nic.go
index 3810c6602..fe557ccbd 100644
--- a/pkg/tcpip/stack/nic.go
+++ b/pkg/tcpip/stack/nic.go
@@ -16,9 +16,9 @@ package stack
 
 import (
 	"strings"
-	"sync"
 	"sync/atomic"
 
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/tcpip"
 	"gvisor.dev/gvisor/pkg/tcpip/buffer"
 	"gvisor.dev/gvisor/pkg/tcpip/header"
diff --git a/pkg/tcpip/stack/stack.go b/pkg/tcpip/stack/stack.go
index 41bf9fd9b..a47ceba54 100644
--- a/pkg/tcpip/stack/stack.go
+++ b/pkg/tcpip/stack/stack.go
@@ -21,13 +21,13 @@ package stack
 
 import (
 	"encoding/binary"
-	"sync"
 	"sync/atomic"
 	"time"
 
 	"golang.org/x/time/rate"
 	"gvisor.dev/gvisor/pkg/rand"
 	"gvisor.dev/gvisor/pkg/sleep"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/tcpip"
 	"gvisor.dev/gvisor/pkg/tcpip/buffer"
 	"gvisor.dev/gvisor/pkg/tcpip/header"
diff --git a/pkg/tcpip/stack/transport_demuxer.go b/pkg/tcpip/stack/transport_demuxer.go
index 67c21be42..f384a91de 100644
--- a/pkg/tcpip/stack/transport_demuxer.go
+++ b/pkg/tcpip/stack/transport_demuxer.go
@@ -18,8 +18,8 @@ import (
 	"fmt"
 	"math/rand"
 	"sort"
-	"sync"
 
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/tcpip"
 	"gvisor.dev/gvisor/pkg/tcpip/hash/jenkins"
 	"gvisor.dev/gvisor/pkg/tcpip/header"
diff --git a/pkg/tcpip/tcpip.go b/pkg/tcpip/tcpip.go
index 72b5ce179..4a090ac86 100644
--- a/pkg/tcpip/tcpip.go
+++ b/pkg/tcpip/tcpip.go
@@ -35,10 +35,10 @@ import (
 	"reflect"
 	"strconv"
 	"strings"
-	"sync"
 	"sync/atomic"
 	"time"
 
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/tcpip/buffer"
 	"gvisor.dev/gvisor/pkg/tcpip/iptables"
 	"gvisor.dev/gvisor/pkg/waiter"
diff --git a/pkg/tcpip/transport/icmp/BUILD b/pkg/tcpip/transport/icmp/BUILD
index d8c5b5058..3aa23d529 100644
--- a/pkg/tcpip/transport/icmp/BUILD
+++ b/pkg/tcpip/transport/icmp/BUILD
@@ -28,6 +28,7 @@ go_library(
     visibility = ["//visibility:public"],
     deps = [
         "//pkg/sleep",
+        "//pkg/sync",
         "//pkg/tcpip",
         "//pkg/tcpip/buffer",
         "//pkg/tcpip/header",
diff --git a/pkg/tcpip/transport/icmp/endpoint.go b/pkg/tcpip/transport/icmp/endpoint.go
index c7ce74cdd..330786f4c 100644
--- a/pkg/tcpip/transport/icmp/endpoint.go
+++ b/pkg/tcpip/transport/icmp/endpoint.go
@@ -15,8 +15,7 @@
 package icmp
 
 import (
-	"sync"
-
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/tcpip"
 	"gvisor.dev/gvisor/pkg/tcpip/buffer"
 	"gvisor.dev/gvisor/pkg/tcpip/header"
diff --git a/pkg/tcpip/transport/packet/BUILD b/pkg/tcpip/transport/packet/BUILD
index 44b58ff6b..4858d150c 100644
--- a/pkg/tcpip/transport/packet/BUILD
+++ b/pkg/tcpip/transport/packet/BUILD
@@ -28,6 +28,7 @@ go_library(
     deps = [
         "//pkg/log",
         "//pkg/sleep",
+        "//pkg/sync",
         "//pkg/tcpip",
         "//pkg/tcpip/buffer",
         "//pkg/tcpip/header",
diff --git a/pkg/tcpip/transport/packet/endpoint.go b/pkg/tcpip/transport/packet/endpoint.go
index 07ffa8aba..fc5bc69fa 100644
--- a/pkg/tcpip/transport/packet/endpoint.go
+++ b/pkg/tcpip/transport/packet/endpoint.go
@@ -25,8 +25,7 @@
 package packet
 
 import (
-	"sync"
-
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/tcpip"
 	"gvisor.dev/gvisor/pkg/tcpip/buffer"
 	"gvisor.dev/gvisor/pkg/tcpip/header"
diff --git a/pkg/tcpip/transport/raw/BUILD b/pkg/tcpip/transport/raw/BUILD
index 00991ac8e..2f2131ff7 100644
--- a/pkg/tcpip/transport/raw/BUILD
+++ b/pkg/tcpip/transport/raw/BUILD
@@ -29,6 +29,7 @@ go_library(
     deps = [
         "//pkg/log",
         "//pkg/sleep",
+        "//pkg/sync",
         "//pkg/tcpip",
         "//pkg/tcpip/buffer",
         "//pkg/tcpip/header",
diff --git a/pkg/tcpip/transport/raw/endpoint.go b/pkg/tcpip/transport/raw/endpoint.go
index 85f7eb76b..ee9c4c58b 100644
--- a/pkg/tcpip/transport/raw/endpoint.go
+++ b/pkg/tcpip/transport/raw/endpoint.go
@@ -26,8 +26,7 @@
 package raw
 
 import (
-	"sync"
-
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/tcpip"
 	"gvisor.dev/gvisor/pkg/tcpip/buffer"
 	"gvisor.dev/gvisor/pkg/tcpip/header"
diff --git a/pkg/tcpip/transport/tcp/BUILD b/pkg/tcpip/transport/tcp/BUILD
index 3b353d56c..353bd06f4 100644
--- a/pkg/tcpip/transport/tcp/BUILD
+++ b/pkg/tcpip/transport/tcp/BUILD
@@ -48,6 +48,7 @@ go_library(
         "//pkg/log",
         "//pkg/rand",
         "//pkg/sleep",
+        "//pkg/sync",
         "//pkg/tcpip",
         "//pkg/tcpip/buffer",
         "//pkg/tcpip/hash/jenkins",
diff --git a/pkg/tcpip/transport/tcp/accept.go b/pkg/tcpip/transport/tcp/accept.go
index 5422ae80c..1ea996936 100644
--- a/pkg/tcpip/transport/tcp/accept.go
+++ b/pkg/tcpip/transport/tcp/accept.go
@@ -19,11 +19,11 @@ import (
 	"encoding/binary"
 	"hash"
 	"io"
-	"sync"
 	"time"
 
 	"gvisor.dev/gvisor/pkg/rand"
 	"gvisor.dev/gvisor/pkg/sleep"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/tcpip"
 	"gvisor.dev/gvisor/pkg/tcpip/buffer"
 	"gvisor.dev/gvisor/pkg/tcpip/header"
diff --git a/pkg/tcpip/transport/tcp/connect.go b/pkg/tcpip/transport/tcp/connect.go
index cdd69f360..613ec1775 100644
--- a/pkg/tcpip/transport/tcp/connect.go
+++ b/pkg/tcpip/transport/tcp/connect.go
@@ -16,11 +16,11 @@ package tcp
 
 import (
 	"encoding/binary"
-	"sync"
 	"time"
 
 	"gvisor.dev/gvisor/pkg/rand"
 	"gvisor.dev/gvisor/pkg/sleep"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/tcpip"
 	"gvisor.dev/gvisor/pkg/tcpip/buffer"
 	"gvisor.dev/gvisor/pkg/tcpip/hash/jenkins"
diff --git a/pkg/tcpip/transport/tcp/endpoint.go b/pkg/tcpip/transport/tcp/endpoint.go
index 830bc1e3e..cca511fb9 100644
--- a/pkg/tcpip/transport/tcp/endpoint.go
+++ b/pkg/tcpip/transport/tcp/endpoint.go
@@ -19,12 +19,12 @@ import (
 	"fmt"
 	"math"
 	"strings"
-	"sync"
 	"sync/atomic"
 	"time"
 
 	"gvisor.dev/gvisor/pkg/rand"
 	"gvisor.dev/gvisor/pkg/sleep"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/tcpip"
 	"gvisor.dev/gvisor/pkg/tcpip/buffer"
 	"gvisor.dev/gvisor/pkg/tcpip/hash/jenkins"
diff --git a/pkg/tcpip/transport/tcp/endpoint_state.go b/pkg/tcpip/transport/tcp/endpoint_state.go
index 7aa4c3f0e..4b8d867bc 100644
--- a/pkg/tcpip/transport/tcp/endpoint_state.go
+++ b/pkg/tcpip/transport/tcp/endpoint_state.go
@@ -16,9 +16,9 @@ package tcp
 
 import (
 	"fmt"
-	"sync"
 	"time"
 
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/tcpip"
 	"gvisor.dev/gvisor/pkg/tcpip/header"
 	"gvisor.dev/gvisor/pkg/tcpip/stack"
diff --git a/pkg/tcpip/transport/tcp/forwarder.go b/pkg/tcpip/transport/tcp/forwarder.go
index 4983bca81..7eb613be5 100644
--- a/pkg/tcpip/transport/tcp/forwarder.go
+++ b/pkg/tcpip/transport/tcp/forwarder.go
@@ -15,8 +15,7 @@
 package tcp
 
 import (
-	"sync"
-
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/tcpip"
 	"gvisor.dev/gvisor/pkg/tcpip/header"
 	"gvisor.dev/gvisor/pkg/tcpip/seqnum"
diff --git a/pkg/tcpip/transport/tcp/protocol.go b/pkg/tcpip/transport/tcp/protocol.go
index bc718064c..9a8f64aa6 100644
--- a/pkg/tcpip/transport/tcp/protocol.go
+++ b/pkg/tcpip/transport/tcp/protocol.go
@@ -22,9 +22,9 @@ package tcp
 
 import (
 	"strings"
-	"sync"
 	"time"
 
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/tcpip"
 	"gvisor.dev/gvisor/pkg/tcpip/buffer"
 	"gvisor.dev/gvisor/pkg/tcpip/header"
diff --git a/pkg/tcpip/transport/tcp/segment_queue.go b/pkg/tcpip/transport/tcp/segment_queue.go
index e0759225e..bd20a7ee9 100644
--- a/pkg/tcpip/transport/tcp/segment_queue.go
+++ b/pkg/tcpip/transport/tcp/segment_queue.go
@@ -15,7 +15,7 @@
 package tcp
 
 import (
-	"sync"
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 // segmentQueue is a bounded, thread-safe queue of TCP segments.
diff --git a/pkg/tcpip/transport/tcp/snd.go b/pkg/tcpip/transport/tcp/snd.go
index 8a947dc66..79f2d274b 100644
--- a/pkg/tcpip/transport/tcp/snd.go
+++ b/pkg/tcpip/transport/tcp/snd.go
@@ -16,11 +16,11 @@ package tcp
 
 import (
 	"math"
-	"sync"
 	"sync/atomic"
 	"time"
 
 	"gvisor.dev/gvisor/pkg/sleep"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/tcpip"
 	"gvisor.dev/gvisor/pkg/tcpip/buffer"
 	"gvisor.dev/gvisor/pkg/tcpip/header"
diff --git a/pkg/tcpip/transport/udp/BUILD b/pkg/tcpip/transport/udp/BUILD
index 97e4d5825..57ff123e3 100644
--- a/pkg/tcpip/transport/udp/BUILD
+++ b/pkg/tcpip/transport/udp/BUILD
@@ -30,6 +30,7 @@ go_library(
     visibility = ["//visibility:public"],
     deps = [
         "//pkg/sleep",
+        "//pkg/sync",
         "//pkg/tcpip",
         "//pkg/tcpip/buffer",
         "//pkg/tcpip/header",
diff --git a/pkg/tcpip/transport/udp/endpoint.go b/pkg/tcpip/transport/udp/endpoint.go
index 864dc8733..a4ff29a7d 100644
--- a/pkg/tcpip/transport/udp/endpoint.go
+++ b/pkg/tcpip/transport/udp/endpoint.go
@@ -15,8 +15,7 @@
 package udp
 
 import (
-	"sync"
-
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/tcpip"
 	"gvisor.dev/gvisor/pkg/tcpip/buffer"
 	"gvisor.dev/gvisor/pkg/tcpip/header"
diff --git a/pkg/tmutex/BUILD b/pkg/tmutex/BUILD
index 6afdb29b7..07778e4f7 100644
--- a/pkg/tmutex/BUILD
+++ b/pkg/tmutex/BUILD
@@ -15,4 +15,5 @@ go_test(
     size = "medium",
     srcs = ["tmutex_test.go"],
     embed = [":tmutex"],
+    deps = ["//pkg/sync"],
 )
diff --git a/pkg/tmutex/tmutex_test.go b/pkg/tmutex/tmutex_test.go
index ce34c7962..05540696a 100644
--- a/pkg/tmutex/tmutex_test.go
+++ b/pkg/tmutex/tmutex_test.go
@@ -17,10 +17,11 @@ package tmutex
 import (
 	"fmt"
 	"runtime"
-	"sync"
 	"sync/atomic"
 	"testing"
 	"time"
+
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 func TestBasicLock(t *testing.T) {
diff --git a/pkg/unet/BUILD b/pkg/unet/BUILD
index 8f6f180e5..d1885ae66 100644
--- a/pkg/unet/BUILD
+++ b/pkg/unet/BUILD
@@ -24,4 +24,5 @@ go_test(
         "unet_test.go",
     ],
     embed = [":unet"],
+    deps = ["//pkg/sync"],
 )
diff --git a/pkg/unet/unet_test.go b/pkg/unet/unet_test.go
index a3cc6f5d3..5c4b9e8e9 100644
--- a/pkg/unet/unet_test.go
+++ b/pkg/unet/unet_test.go
@@ -19,10 +19,11 @@ import (
 	"os"
 	"path/filepath"
 	"reflect"
-	"sync"
 	"syscall"
 	"testing"
 	"time"
+
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 func randomFilename() (string, error) {
diff --git a/pkg/urpc/BUILD b/pkg/urpc/BUILD
index b6bbb0ea2..b8fdc3125 100644
--- a/pkg/urpc/BUILD
+++ b/pkg/urpc/BUILD
@@ -11,6 +11,7 @@ go_library(
     deps = [
         "//pkg/fd",
         "//pkg/log",
+        "//pkg/sync",
         "//pkg/unet",
     ],
 )
diff --git a/pkg/urpc/urpc.go b/pkg/urpc/urpc.go
index df59ffab1..13b2ea314 100644
--- a/pkg/urpc/urpc.go
+++ b/pkg/urpc/urpc.go
@@ -27,10 +27,10 @@ import (
 	"os"
 	"reflect"
 	"runtime"
-	"sync"
 
 	"gvisor.dev/gvisor/pkg/fd"
 	"gvisor.dev/gvisor/pkg/log"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/unet"
 )
 
diff --git a/pkg/waiter/BUILD b/pkg/waiter/BUILD
index 0427bc41f..1c6890e52 100644
--- a/pkg/waiter/BUILD
+++ b/pkg/waiter/BUILD
@@ -24,6 +24,7 @@ go_library(
     ],
     importpath = "gvisor.dev/gvisor/pkg/waiter",
     visibility = ["//visibility:public"],
+    deps = ["//pkg/sync"],
 )
 
 go_test(
diff --git a/pkg/waiter/waiter.go b/pkg/waiter/waiter.go
index 8a65ed164..f708e95fa 100644
--- a/pkg/waiter/waiter.go
+++ b/pkg/waiter/waiter.go
@@ -58,7 +58,7 @@
 package waiter
 
 import (
-	"sync"
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 // EventMask represents io events as used in the poll() syscall.
diff --git a/runsc/boot/BUILD b/runsc/boot/BUILD
index 6226b63f8..3e20f8f2f 100644
--- a/runsc/boot/BUILD
+++ b/runsc/boot/BUILD
@@ -74,6 +74,7 @@ go_library(
         "//pkg/sentry/usage",
         "//pkg/sentry/usermem",
         "//pkg/sentry/watchdog",
+        "//pkg/sync",
         "//pkg/syserror",
         "//pkg/tcpip",
         "//pkg/tcpip/link/fdbased",
@@ -114,6 +115,7 @@ go_test(
         "//pkg/sentry/context/contexttest",
         "//pkg/sentry/fs",
         "//pkg/sentry/kernel/auth",
+        "//pkg/sync",
         "//pkg/unet",
         "//runsc/fsgofer",
         "@com_github_opencontainers_runtime-spec//specs-go:go_default_library",
diff --git a/runsc/boot/compat.go b/runsc/boot/compat.go
index 352e710d2..9c23b9553 100644
--- a/runsc/boot/compat.go
+++ b/runsc/boot/compat.go
@@ -17,7 +17,6 @@ package boot
 import (
 	"fmt"
 	"os"
-	"sync"
 	"syscall"
 
 	"github.com/golang/protobuf/proto"
@@ -27,6 +26,7 @@ import (
 	ucspb "gvisor.dev/gvisor/pkg/sentry/kernel/uncaught_signal_go_proto"
 	"gvisor.dev/gvisor/pkg/sentry/strace"
 	spb "gvisor.dev/gvisor/pkg/sentry/unimpl/unimplemented_syscall_go_proto"
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 func initCompatLogs(fd int) error {
diff --git a/runsc/boot/limits.go b/runsc/boot/limits.go
index d1c0bb9b5..ce62236e5 100644
--- a/runsc/boot/limits.go
+++ b/runsc/boot/limits.go
@@ -16,12 +16,12 @@ package boot
 
 import (
 	"fmt"
-	"sync"
 	"syscall"
 
 	specs "github.com/opencontainers/runtime-spec/specs-go"
 	"gvisor.dev/gvisor/pkg/log"
 	"gvisor.dev/gvisor/pkg/sentry/limits"
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 // Mapping from linux resource names to limits.LimitType.
diff --git a/runsc/boot/loader.go b/runsc/boot/loader.go
index bc1d0c1bb..fad72f4ab 100644
--- a/runsc/boot/loader.go
+++ b/runsc/boot/loader.go
@@ -20,7 +20,6 @@ import (
 	mrand "math/rand"
 	"os"
 	"runtime"
-	"sync"
 	"sync/atomic"
 	"syscall"
 	gtime "time"
@@ -46,6 +45,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/time"
 	"gvisor.dev/gvisor/pkg/sentry/usage"
 	"gvisor.dev/gvisor/pkg/sentry/watchdog"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/tcpip"
 	"gvisor.dev/gvisor/pkg/tcpip/link/sniffer"
 	"gvisor.dev/gvisor/pkg/tcpip/network/arp"
diff --git a/runsc/boot/loader_test.go b/runsc/boot/loader_test.go
index 147ff7703..bec0dc292 100644
--- a/runsc/boot/loader_test.go
+++ b/runsc/boot/loader_test.go
@@ -19,7 +19,6 @@ import (
 	"math/rand"
 	"os"
 	"reflect"
-	"sync"
 	"syscall"
 	"testing"
 	"time"
@@ -30,6 +29,7 @@ import (
 	"gvisor.dev/gvisor/pkg/p9"
 	"gvisor.dev/gvisor/pkg/sentry/context/contexttest"
 	"gvisor.dev/gvisor/pkg/sentry/fs"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/unet"
 	"gvisor.dev/gvisor/runsc/fsgofer"
 )
diff --git a/runsc/cmd/BUILD b/runsc/cmd/BUILD
index 250845ad7..b94bc4fa0 100644
--- a/runsc/cmd/BUILD
+++ b/runsc/cmd/BUILD
@@ -44,6 +44,7 @@ go_library(
         "//pkg/sentry/control",
         "//pkg/sentry/kernel",
         "//pkg/sentry/kernel/auth",
+        "//pkg/sync",
         "//pkg/unet",
         "//pkg/urpc",
         "//runsc/boot",
diff --git a/runsc/cmd/create.go b/runsc/cmd/create.go
index a4e3071b3..1815c93b9 100644
--- a/runsc/cmd/create.go
+++ b/runsc/cmd/create.go
@@ -16,6 +16,7 @@ package cmd
 
 import (
 	"context"
+
 	"flag"
 	"github.com/google/subcommands"
 	"gvisor.dev/gvisor/runsc/boot"
diff --git a/runsc/cmd/gofer.go b/runsc/cmd/gofer.go
index 4831210c0..7df7995f0 100644
--- a/runsc/cmd/gofer.go
+++ b/runsc/cmd/gofer.go
@@ -21,7 +21,6 @@ import (
 	"os"
 	"path/filepath"
 	"strings"
-	"sync"
 	"syscall"
 
 	"flag"
@@ -30,6 +29,7 @@ import (
 	"golang.org/x/sys/unix"
 	"gvisor.dev/gvisor/pkg/log"
 	"gvisor.dev/gvisor/pkg/p9"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/unet"
 	"gvisor.dev/gvisor/runsc/boot"
 	"gvisor.dev/gvisor/runsc/fsgofer"
diff --git a/runsc/cmd/start.go b/runsc/cmd/start.go
index de2115dff..5e9bc53ab 100644
--- a/runsc/cmd/start.go
+++ b/runsc/cmd/start.go
@@ -16,6 +16,7 @@ package cmd
 
 import (
 	"context"
+
 	"flag"
 	"github.com/google/subcommands"
 	"gvisor.dev/gvisor/runsc/boot"
diff --git a/runsc/container/BUILD b/runsc/container/BUILD
index 2bd12120d..6dea179e4 100644
--- a/runsc/container/BUILD
+++ b/runsc/container/BUILD
@@ -18,6 +18,7 @@ go_library(
     deps = [
         "//pkg/log",
         "//pkg/sentry/control",
+        "//pkg/sync",
         "//runsc/boot",
         "//runsc/cgroup",
         "//runsc/sandbox",
@@ -53,6 +54,7 @@ go_test(
         "//pkg/sentry/control",
         "//pkg/sentry/kernel",
         "//pkg/sentry/kernel/auth",
+        "//pkg/sync",
         "//pkg/unet",
         "//pkg/urpc",
         "//runsc/boot",
diff --git a/runsc/container/console_test.go b/runsc/container/console_test.go
index 5ed131a7f..060b63bf3 100644
--- a/runsc/container/console_test.go
+++ b/runsc/container/console_test.go
@@ -20,7 +20,6 @@ import (
 	"io"
 	"os"
 	"path/filepath"
-	"sync"
 	"syscall"
 	"testing"
 	"time"
@@ -29,6 +28,7 @@ import (
 	"golang.org/x/sys/unix"
 	"gvisor.dev/gvisor/pkg/sentry/control"
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/unet"
 	"gvisor.dev/gvisor/pkg/urpc"
 	"gvisor.dev/gvisor/runsc/testutil"
diff --git a/runsc/container/container_test.go b/runsc/container/container_test.go
index c10f85992..b54d8f712 100644
--- a/runsc/container/container_test.go
+++ b/runsc/container/container_test.go
@@ -26,7 +26,6 @@ import (
 	"reflect"
 	"strconv"
 	"strings"
-	"sync"
 	"syscall"
 	"testing"
 	"time"
@@ -39,6 +38,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/control"
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/runsc/boot"
 	"gvisor.dev/gvisor/runsc/boot/platforms"
 	"gvisor.dev/gvisor/runsc/specutils"
diff --git a/runsc/container/multi_container_test.go b/runsc/container/multi_container_test.go
index 4ad09ceab..2da93ec5b 100644
--- a/runsc/container/multi_container_test.go
+++ b/runsc/container/multi_container_test.go
@@ -22,7 +22,6 @@ import (
 	"path"
 	"path/filepath"
 	"strings"
-	"sync"
 	"syscall"
 	"testing"
 	"time"
@@ -30,6 +29,7 @@ import (
 	specs "github.com/opencontainers/runtime-spec/specs-go"
 	"gvisor.dev/gvisor/pkg/sentry/control"
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/runsc/boot"
 	"gvisor.dev/gvisor/runsc/specutils"
 	"gvisor.dev/gvisor/runsc/testutil"
diff --git a/runsc/container/state_file.go b/runsc/container/state_file.go
index d95151ea5..17a251530 100644
--- a/runsc/container/state_file.go
+++ b/runsc/container/state_file.go
@@ -20,10 +20,10 @@ import (
 	"io/ioutil"
 	"os"
 	"path/filepath"
-	"sync"
 
 	"github.com/gofrs/flock"
 	"gvisor.dev/gvisor/pkg/log"
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 const stateFileExtension = ".state"
diff --git a/runsc/fsgofer/BUILD b/runsc/fsgofer/BUILD
index afcb41801..a9582d92b 100644
--- a/runsc/fsgofer/BUILD
+++ b/runsc/fsgofer/BUILD
@@ -19,6 +19,7 @@ go_library(
         "//pkg/fd",
         "//pkg/log",
         "//pkg/p9",
+        "//pkg/sync",
         "//pkg/syserr",
         "//runsc/specutils",
         "@org_golang_x_sys//unix:go_default_library",
diff --git a/runsc/fsgofer/fsgofer.go b/runsc/fsgofer/fsgofer.go
index b59e1a70e..93606d051 100644
--- a/runsc/fsgofer/fsgofer.go
+++ b/runsc/fsgofer/fsgofer.go
@@ -29,7 +29,6 @@ import (
 	"path/filepath"
 	"runtime"
 	"strconv"
-	"sync"
 	"syscall"
 
 	"golang.org/x/sys/unix"
@@ -37,6 +36,7 @@ import (
 	"gvisor.dev/gvisor/pkg/fd"
 	"gvisor.dev/gvisor/pkg/log"
 	"gvisor.dev/gvisor/pkg/p9"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/runsc/specutils"
 )
 
diff --git a/runsc/sandbox/BUILD b/runsc/sandbox/BUILD
index 8001949d5..ddbc37456 100644
--- a/runsc/sandbox/BUILD
+++ b/runsc/sandbox/BUILD
@@ -19,6 +19,7 @@ go_library(
         "//pkg/log",
         "//pkg/sentry/control",
         "//pkg/sentry/platform",
+        "//pkg/sync",
         "//pkg/tcpip/header",
         "//pkg/tcpip/stack",
         "//pkg/urpc",
diff --git a/runsc/sandbox/sandbox.go b/runsc/sandbox/sandbox.go
index ce1452b87..ec72bdbfd 100644
--- a/runsc/sandbox/sandbox.go
+++ b/runsc/sandbox/sandbox.go
@@ -22,7 +22,6 @@ import (
 	"os"
 	"os/exec"
 	"strconv"
-	"sync"
 	"syscall"
 	"time"
 
@@ -34,6 +33,7 @@ import (
 	"gvisor.dev/gvisor/pkg/log"
 	"gvisor.dev/gvisor/pkg/sentry/control"
 	"gvisor.dev/gvisor/pkg/sentry/platform"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/urpc"
 	"gvisor.dev/gvisor/runsc/boot"
 	"gvisor.dev/gvisor/runsc/boot/platforms"
diff --git a/runsc/testutil/BUILD b/runsc/testutil/BUILD
index c96ca2eb6..3c3027cb5 100644
--- a/runsc/testutil/BUILD
+++ b/runsc/testutil/BUILD
@@ -10,6 +10,7 @@ go_library(
     visibility = ["//:sandbox"],
     deps = [
         "//pkg/log",
+        "//pkg/sync",
         "//runsc/boot",
         "//runsc/specutils",
         "@com_github_cenkalti_backoff//:go_default_library",
diff --git a/runsc/testutil/testutil.go b/runsc/testutil/testutil.go
index 9632776d2..fb22eae39 100644
--- a/runsc/testutil/testutil.go
+++ b/runsc/testutil/testutil.go
@@ -34,7 +34,6 @@ import (
 	"path/filepath"
 	"strconv"
 	"strings"
-	"sync"
 	"sync/atomic"
 	"syscall"
 	"time"
@@ -42,6 +41,7 @@ import (
 	"github.com/cenkalti/backoff"
 	specs "github.com/opencontainers/runtime-spec/specs-go"
 	"gvisor.dev/gvisor/pkg/log"
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/runsc/boot"
 	"gvisor.dev/gvisor/runsc/specutils"
 )
-- 
cgit v1.2.3


From dacd349d6fb4fc7453b1fbf694158fd25496ed42 Mon Sep 17 00:00:00 2001
From: Bhasker Hariharan <bhaskerh@google.com>
Date: Fri, 10 Jan 2020 06:01:10 -0800
Subject: panic fix in retransmitTimerExpired.

This is a band-aid fix for now to prevent panics.

PiperOrigin-RevId: 289078453
---
 pkg/tcpip/transport/tcp/snd.go | 7 +++++++
 1 file changed, 7 insertions(+)

(limited to 'pkg/tcpip/transport/tcp')

diff --git a/pkg/tcpip/transport/tcp/snd.go b/pkg/tcpip/transport/tcp/snd.go
index 79f2d274b..fdff7ed81 100644
--- a/pkg/tcpip/transport/tcp/snd.go
+++ b/pkg/tcpip/transport/tcp/snd.go
@@ -442,6 +442,13 @@ func (s *sender) retransmitTimerExpired() bool {
 		return true
 	}
 
+	// TODO(b/147297758): Band-aid fix, retransmitTimer can fire in some edge cases
+	// when writeList is empty. Remove this once we have a proper fix for this
+	// issue.
+	if s.writeList.Front() == nil {
+		return true
+	}
+
 	s.ep.stack.Stats().TCP.Timeouts.Increment()
 	s.ep.stats.SendErrors.Timeouts.Increment()
 
-- 
cgit v1.2.3