Merge release-20200211.0-33-g906eb62 (automated)

6 files changed, 36 insertions, 248 deletions

diff --git a/pkg/atomicbitops/atomic_bitops_arm64.s b/pkg/atomicbitops/atomic_bitops_arm64.s
deleted file mode 100755
index 97f8808c1..000000000
--- a/pkg/atomicbitops/atomic_bitops_arm64.s
+++ /dev/null
@@ -1,139 +0,0 @@
-// Copyright 2019 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.
-
-// +build arm64
-
-#include "textflag.h"
-
-TEXT ·AndUint32(SB),$0-12
-  MOVD    ptr+0(FP), R0
-  MOVW    val+8(FP), R1
-again:
-  LDAXRW  (R0), R2
-  ANDW    R1, R2
-  STLXRW  R2, (R0), R3
-  CBNZ    R3, again
-  RET
-
-TEXT ·OrUint32(SB),$0-12
-  MOVD    ptr+0(FP), R0
-  MOVW    val+8(FP), R1
-again:
-  LDAXRW  (R0), R2
-  ORRW    R1, R2
-  STLXRW  R2, (R0), R3
-  CBNZ    R3, again
-  RET
-
-TEXT ·XorUint32(SB),$0-12
-  MOVD    ptr+0(FP), R0
-  MOVW    val+8(FP), R1
-again:
-  LDAXRW  (R0), R2
-  EORW    R1, R2
-  STLXRW  R2, (R0), R3
-  CBNZ    R3, again
-  RET
-
-TEXT ·CompareAndSwapUint32(SB),$0-20
-  MOVD addr+0(FP), R0
-  MOVW old+8(FP), R1
-  MOVW new+12(FP), R2
-
-again:
-  LDAXRW (R0), R3
-  CMPW R1, R3
-  BNE done
-  STLXRW R2, (R0), R4
-  CBNZ R4, again
-done:
-  MOVW R3, prev+16(FP)
-  RET
-
-TEXT ·AndUint64(SB),$0-16
-  MOVD    ptr+0(FP), R0
-  MOVD    val+8(FP), R1
-again:
-  LDAXR   (R0), R2
-  AND     R1, R2
-  STLXR   R2, (R0), R3
-  CBNZ    R3, again
-  RET
-
-TEXT ·OrUint64(SB),$0-16
-  MOVD    ptr+0(FP), R0
-  MOVD    val+8(FP), R1
-again:
-  LDAXR   (R0), R2
-  ORR     R1, R2
-  STLXR   R2, (R0), R3
-  CBNZ    R3, again
-  RET
-
-TEXT ·XorUint64(SB),$0-16
-  MOVD    ptr+0(FP), R0
-  MOVD    val+8(FP), R1
-again:
-  LDAXR   (R0), R2
-  EOR     R1, R2
-  STLXR   R2, (R0), R3
-  CBNZ    R3, again
-  RET
-
-TEXT ·CompareAndSwapUint64(SB),$0-32
-  MOVD addr+0(FP), R0
-  MOVD old+8(FP), R1
-  MOVD new+16(FP), R2
-
-again:
-  LDAXR (R0), R3
-  CMP R1, R3
-  BNE done
-  STLXR R2, (R0), R4
-  CBNZ R4, again
-done:
-  MOVD R3, prev+24(FP)
-  RET
-
-TEXT ·IncUnlessZeroInt32(SB),NOSPLIT,$0-9
-  MOVD addr+0(FP), R0
-
-again:
-  LDAXRW (R0), R1
-  CBZ R1, fail
-  ADDW $1, R1
-  STLXRW R1, (R0), R2
-  CBNZ R2, again
-  MOVW $1, R2
-  MOVB R2, ret+8(FP)
-  RET
-fail:
-  MOVB ZR, ret+8(FP)
-  RET
-
-TEXT ·DecUnlessOneInt32(SB),NOSPLIT,$0-9
-  MOVD addr+0(FP), R0
-
-again:
-  LDAXRW (R0), R1
-  SUBSW $1, R1, R1
-  BEQ fail
-  STLXRW R1, (R0), R2
-  CBNZ R2, again
-  MOVW $1, R2
-  MOVB R2, ret+8(FP)
-  RET
-fail:
-  MOVB ZR, ret+8(FP)
-  RET
diff --git a/pkg/atomicbitops/atomic_bitops.go b/pkg/atomicbitops/atomicbitops.go
index fcc41a9ea..1be081719 100644..100755
--- a/pkg/atomicbitops/atomic_bitops.go
+++ b/pkg/atomicbitops/atomicbitops.go
@@ -14,47 +14,34 @@
 
 // +build amd64 arm64
 
-// Package atomicbitops provides basic bitwise operations in an atomic way.
-// The implementation on amd64 leverages the LOCK prefix directly instead of
-// relying on the generic cas primitives, and the arm64 leverages the LDAXR
-// and STLXR pair primitives.
+// Package atomicbitops provides extensions to the sync/atomic package.
 //
-// WARNING: the bitwise ops provided in this package doesn't imply any memory
-// ordering. Using them to construct locks must employ proper memory barriers.
+// All read-modify-write operations implemented by this package have
+// acquire-release memory ordering (like sync/atomic).
 package atomicbitops
 
-// AndUint32 atomically applies bitwise and operation to *addr with val.
+// AndUint32 atomically applies bitwise AND operation to *addr with val.
 func AndUint32(addr *uint32, val uint32)
 
-// OrUint32 atomically applies bitwise or operation to *addr with val.
+// OrUint32 atomically applies bitwise OR operation to *addr with val.
 func OrUint32(addr *uint32, val uint32)
 
-// XorUint32 atomically applies bitwise xor operation to *addr with val.
+// XorUint32 atomically applies bitwise XOR operation to *addr with val.
 func XorUint32(addr *uint32, val uint32)
 
 // CompareAndSwapUint32 is like sync/atomic.CompareAndSwapUint32, but returns
 // the value previously stored at addr.
 func CompareAndSwapUint32(addr *uint32, old, new uint32) uint32
 
-// AndUint64 atomically applies bitwise and operation to *addr with val.
+// AndUint64 atomically applies bitwise AND operation to *addr with val.
 func AndUint64(addr *uint64, val uint64)
 
-// OrUint64 atomically applies bitwise or operation to *addr with val.
+// OrUint64 atomically applies bitwise OR operation to *addr with val.
 func OrUint64(addr *uint64, val uint64)
 
-// XorUint64 atomically applies bitwise xor operation to *addr with val.
+// XorUint64 atomically applies bitwise XOR operation to *addr with val.
 func XorUint64(addr *uint64, val uint64)
 
 // CompareAndSwapUint64 is like sync/atomic.CompareAndSwapUint64, but returns
 // the value previously stored at addr.
 func CompareAndSwapUint64(addr *uint64, old, new uint64) uint64
-
-// IncUnlessZeroInt32 increments the value stored at the given address and
-// returns true; unless the value stored in the pointer is zero, in which case
-// it is left unmodified and false is returned.
-func IncUnlessZeroInt32(addr *int32) bool
-
-// DecUnlessOneInt32 decrements the value stored at the given address and
-// returns true; unless the value stored in the pointer is 1, in which case it
-// is left unmodified and false is returned.
-func DecUnlessOneInt32(addr *int32) bool
diff --git a/pkg/atomicbitops/atomic_bitops_amd64.s b/pkg/atomicbitops/atomicbitops_amd64.s
index db0972001..54c887ee5 100644..100755
--- a/pkg/atomicbitops/atomic_bitops_amd64.s
+++ b/pkg/atomicbitops/atomicbitops_amd64.s
@@ -75,41 +75,3 @@ TEXT ·CompareAndSwapUint64(SB),$0-32
   CMPXCHGQ DX, 0(DI)
   MOVQ  AX, ret+24(FP)
   RET
-
-TEXT ·IncUnlessZeroInt32(SB),NOSPLIT,$0-9
-  MOVQ     addr+0(FP), DI
-  MOVL     0(DI), AX
-
-retry:
-  TESTL    AX, AX
-  JZ       fail
-  LEAL     1(AX), DX
-  LOCK
-  CMPXCHGL DX, 0(DI)
-  JNZ      retry
-
-  SETEQ    ret+8(FP)
-  RET
-
-fail:
-  MOVB     AX, ret+8(FP)
-  RET
-
-TEXT ·DecUnlessOneInt32(SB),NOSPLIT,$0-9
-  MOVQ     addr+0(FP), DI
-  MOVL     0(DI), AX
-
-retry:
-  LEAL     -1(AX), DX
-  TESTL    DX, DX
-  JZ       fail
-  LOCK
-  CMPXCHGL DX, 0(DI)
-  JNZ      retry
-
-  SETEQ    ret+8(FP)
-  RET
-
-fail:
-  MOVB     DX, ret+8(FP)
-  RET
diff --git a/pkg/atomicbitops/atomic_bitops_common.go b/pkg/atomicbitops/atomicbitops_noasm.go
index 85163ad62..3b2898256 100644..100755
--- a/pkg/atomicbitops/atomic_bitops_common.go
+++ b/pkg/atomicbitops/atomicbitops_noasm.go
@@ -20,7 +20,6 @@ import (
 	"sync/atomic"
 )
 
-// AndUint32 atomically applies bitwise and operation to *addr with val.
 func AndUint32(addr *uint32, val uint32) {
 	for {
 		o := atomic.LoadUint32(addr)
@@ -31,7 +30,6 @@ func AndUint32(addr *uint32, val uint32) {
 	}
 }
 
-// OrUint32 atomically applies bitwise or operation to *addr with val.
 func OrUint32(addr *uint32, val uint32) {
 	for {
 		o := atomic.LoadUint32(addr)
@@ -42,7 +40,6 @@ func OrUint32(addr *uint32, val uint32) {
 	}
 }
 
-// XorUint32 atomically applies bitwise xor operation to *addr with val.
 func XorUint32(addr *uint32, val uint32) {
 	for {
 		o := atomic.LoadUint32(addr)
@@ -53,8 +50,6 @@ func XorUint32(addr *uint32, val uint32) {
 	}
 }
 
-// CompareAndSwapUint32 is like sync/atomic.CompareAndSwapUint32, but returns
-// the value previously stored at addr.
 func CompareAndSwapUint32(addr *uint32, old, new uint32) (prev uint32) {
 	for {
 		prev = atomic.LoadUint32(addr)
@@ -67,7 +62,6 @@ func CompareAndSwapUint32(addr *uint32, old, new uint32) (prev uint32) {
 	}
 }
 
-// AndUint64 atomically applies bitwise and operation to *addr with val.
 func AndUint64(addr *uint64, val uint64) {
 	for {
 		o := atomic.LoadUint64(addr)
@@ -78,7 +72,6 @@ func AndUint64(addr *uint64, val uint64) {
 	}
 }
 
-// OrUint64 atomically applies bitwise or operation to *addr with val.
 func OrUint64(addr *uint64, val uint64) {
 	for {
 		o := atomic.LoadUint64(addr)
@@ -89,7 +82,6 @@ func OrUint64(addr *uint64, val uint64) {
 	}
 }
 
-// XorUint64 atomically applies bitwise xor operation to *addr with val.
 func XorUint64(addr *uint64, val uint64) {
 	for {
 		o := atomic.LoadUint64(addr)
@@ -100,8 +92,6 @@ func XorUint64(addr *uint64, val uint64) {
 	}
 }
 
-// CompareAndSwapUint64 is like sync/atomic.CompareAndSwapUint64, but returns
-// the value previously stored at addr.
 func CompareAndSwapUint64(addr *uint64, old, new uint64) (prev uint64) {
 	for {
 		prev = atomic.LoadUint64(addr)
@@ -113,35 +103,3 @@ func CompareAndSwapUint64(addr *uint64, old, new uint64) (prev uint64) {
 		}
 	}
 }
-
-// IncUnlessZeroInt32 increments the value stored at the given address and
-// returns true; unless the value stored in the pointer is zero, in which case
-// it is left unmodified and false is returned.
-func IncUnlessZeroInt32(addr *int32) bool {
-	for {
-		v := atomic.LoadInt32(addr)
-		if v == 0 {
-			return false
-		}
-
-		if atomic.CompareAndSwapInt32(addr, v, v+1) {
-			return true
-		}
-	}
-}
-
-// DecUnlessOneInt32 decrements the value stored at the given address and
-// returns true; unless the value stored in the pointer is 1, in which case it
-// is left unmodified and false is returned.
-func DecUnlessOneInt32(addr *int32) bool {
-	for {
-		v := atomic.LoadInt32(addr)
-		if v == 1 {
-			return false
-		}
-
-		if atomic.CompareAndSwapInt32(addr, v, v-1) {
-			return true
-		}
-	}
-}
diff --git a/pkg/sentry/mm/address_space.go b/pkg/sentry/mm/address_space.go
index e58a63deb..94d39af60 100644
--- a/pkg/sentry/mm/address_space.go
+++ b/pkg/sentry/mm/address_space.go
@@ -18,7 +18,6 @@ import (
 	"fmt"
 	"sync/atomic"
 
-	"gvisor.dev/gvisor/pkg/atomicbitops"
 	"gvisor.dev/gvisor/pkg/sentry/platform"
 	"gvisor.dev/gvisor/pkg/usermem"
 )
@@ -42,8 +41,15 @@ func (mm *MemoryManager) AddressSpace() platform.AddressSpace {
 func (mm *MemoryManager) Activate() error {
 	// Fast path: the MemoryManager already has an active
 	// platform.AddressSpace, and we just need to indicate that we need it too.
-	if atomicbitops.IncUnlessZeroInt32(&mm.active) {
-		return nil
+	for {
+		active := atomic.LoadInt32(&mm.active)
+		if active == 0 {
+			// Fall back to the slow path.
+			break
+		}
+		if atomic.CompareAndSwapInt32(&mm.active, active, active+1) {
+			return nil
+		}
 	}
 
 	for {
@@ -118,8 +124,15 @@ func (mm *MemoryManager) Activate() error {
 func (mm *MemoryManager) Deactivate() {
 	// Fast path: this is not the last goroutine to deactivate the
 	// MemoryManager.
-	if atomicbitops.DecUnlessOneInt32(&mm.active) {
-		return
+	for {
+		active := atomic.LoadInt32(&mm.active)
+		if active == 1 {
+			// Fall back to the slow path.
+			break
+		}
+		if atomic.CompareAndSwapInt32(&mm.active, active, active-1) {
+			return
+		}
 	}
 
 	mm.activeMu.Lock()
diff --git a/pkg/sentry/mm/lifecycle.go b/pkg/sentry/mm/lifecycle.go
index 47b8fbf43..3c263ebaa 100644
--- a/pkg/sentry/mm/lifecycle.go
+++ b/pkg/sentry/mm/lifecycle.go
@@ -18,7 +18,6 @@ import (
 	"fmt"
 	"sync/atomic"
 
-	"gvisor.dev/gvisor/pkg/atomicbitops"
 	"gvisor.dev/gvisor/pkg/context"
 	"gvisor.dev/gvisor/pkg/sentry/arch"
 	"gvisor.dev/gvisor/pkg/sentry/limits"
@@ -229,7 +228,15 @@ func (mm *MemoryManager) Fork(ctx context.Context) (*MemoryManager, error) {
 // IncUsers increments mm's user count and returns true. If the user count is
 // already 0, IncUsers does nothing and returns false.
 func (mm *MemoryManager) IncUsers() bool {
-	return atomicbitops.IncUnlessZeroInt32(&mm.users)
+	for {
+		users := atomic.LoadInt32(&mm.users)
+		if users == 0 {
+			return false
+		}
+		if atomic.CompareAndSwapInt32(&mm.users, users, users+1) {
+			return true
+		}
+	}
 }
 
 // DecUsers decrements mm's user count. If the user count reaches 0, all