Consolidate most synchronization primitive linknames in the sync package.

PiperOrigin-RevId: 345359823

10 files changed, 172 insertions, 61 deletions

diff --git a/pkg/sync/BUILD b/pkg/sync/BUILD
index 5bd4d09d1..be5bc99fc 100644
--- a/pkg/sync/BUILD
+++ b/pkg/sync/BUILD
@@ -33,15 +33,17 @@ go_library(
         "aliases.go",
         "checklocks_off_unsafe.go",
         "checklocks_on_unsafe.go",
-        "memmove_unsafe.go",
+        "goyield_go113_unsafe.go",
+        "goyield_unsafe.go",
         "mutex_unsafe.go",
         "nocopy.go",
         "norace_unsafe.go",
+        "race_amd64.s",
+        "race_arm64.s",
         "race_unsafe.go",
+        "runtime_unsafe.go",
         "rwmutex_unsafe.go",
         "seqcount.go",
-        "spin_legacy_unsafe.go",
-        "spin_unsafe.go",
         "sync.go",
     ],
     marshal = False,
diff --git a/pkg/sync/spin_legacy_unsafe.go b/pkg/sync/goyield_go113_unsafe.go
index 61fc7320e..8aee0d455 100644
--- a/pkg/sync/spin_legacy_unsafe.go
+++ b/pkg/sync/goyield_go113_unsafe.go
@@ -10,15 +10,8 @@ package sync
 
 import (
 	"runtime"
-	_ "unsafe" // for go:linkname
 )
 
-//go:linkname canSpin sync.runtime_canSpin
-func canSpin(i int) bool
-
-//go:linkname doSpin sync.runtime_doSpin
-func doSpin()
-
 func goyield() {
 	// goyield is not available until Go 1.14.
 	runtime.Gosched()
diff --git a/pkg/sync/spin_unsafe.go b/pkg/sync/goyield_unsafe.go
index 18e8fc743..672ee274d 100644
--- a/pkg/sync/spin_unsafe.go
+++ b/pkg/sync/goyield_unsafe.go
@@ -14,11 +14,5 @@ import (
 	_ "unsafe" // for go:linkname
 )
 
-//go:linkname canSpin sync.runtime_canSpin
-func canSpin(i int) bool
-
-//go:linkname doSpin sync.runtime_doSpin
-func doSpin()
-
 //go:linkname goyield runtime.goyield
 func goyield()
diff --git a/pkg/sync/memmove_unsafe.go b/pkg/sync/memmove_unsafe.go
deleted file mode 100644
index f5e630009..000000000
--- a/pkg/sync/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 !go1.17
-
-// 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
index 006055dd6..70b5f3a5e 100644
--- a/pkg/sync/norace_unsafe.go
+++ b/pkg/sync/norace_unsafe.go
@@ -8,6 +8,7 @@
 package sync
 
 import (
+	"sync/atomic"
 	"unsafe"
 )
 
@@ -33,3 +34,13 @@ func RaceRelease(addr unsafe.Pointer) {
 // RaceReleaseMerge has the same semantics as runtime.RaceReleaseMerge.
 func RaceReleaseMerge(addr unsafe.Pointer) {
 }
+
+// RaceUncheckedAtomicCompareAndSwapUintptr is equivalent to
+// sync/atomic.CompareAndSwapUintptr, but is not checked by the race detector.
+// This is necessary when implementing gopark callbacks, since no race context
+// is available during their execution.
+func RaceUncheckedAtomicCompareAndSwapUintptr(ptr *uintptr, old, new uintptr) bool {
+	// Use atomic.CompareAndSwapUintptr outside of race builds for
+	// inlinability.
+	return atomic.CompareAndSwapUintptr(ptr, old, new)
+}
diff --git a/pkg/sync/race_amd64.s b/pkg/sync/race_amd64.s
new file mode 100644
index 000000000..57bc0ec79
--- /dev/null
+++ b/pkg/sync/race_amd64.s
@@ -0,0 +1,33 @@
+// Copyright 2020 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 race
+// +build amd64
+
+#include "textflag.h"
+
+// func RaceUncheckedAtomicCompareAndSwapUintptr(ptr *uintptr, old, new uintptr) bool
+TEXT ·RaceUncheckedAtomicCompareAndSwapUintptr(SB),NOSPLIT,$0-25
+	MOVQ ptr+0(FP), DI
+	MOVQ old+8(FP), AX
+	MOVQ new+16(FP), SI
+
+	LOCK
+	CMPXCHGQ SI, 0(DI)
+
+	SETEQ AX
+	MOVB AX, ret+24(FP)
+
+	RET
+
diff --git a/pkg/sync/race_arm64.s b/pkg/sync/race_arm64.s
new file mode 100644
index 000000000..88f091fda
--- /dev/null
+++ b/pkg/sync/race_arm64.s
@@ -0,0 +1,35 @@
+// Copyright 2020 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 race
+// +build arm64
+
+#include "textflag.h"
+
+// func RaceUncheckedAtomicCompareAndSwapUintptr(ptr *uintptr, old, new uintptr) bool
+TEXT ·RaceUncheckedAtomicCompareAndSwapUintptr(SB),NOSPLIT,$0-25
+	MOVD ptr+0(FP), R0
+	MOVD old+8(FP), R1
+	MOVD new+16(FP), R1
+again:
+	LDAXR (R0), R3
+	CMP R1, R3
+	BNE ok
+	STLXR R2, (R0), R3
+	CBNZ R3, again
+ok:
+	CSET EQ, R0
+	MOVB R0, ret+24(FP)
+	RET
+
diff --git a/pkg/sync/race_unsafe.go b/pkg/sync/race_unsafe.go
index 31d8fa9a6..59985c270 100644
--- a/pkg/sync/race_unsafe.go
+++ b/pkg/sync/race_unsafe.go
@@ -39,3 +39,9 @@ func RaceRelease(addr unsafe.Pointer) {
 func RaceReleaseMerge(addr unsafe.Pointer) {
 	runtime.RaceReleaseMerge(addr)
 }
+
+// RaceUncheckedAtomicCompareAndSwapUintptr is equivalent to
+// sync/atomic.CompareAndSwapUintptr, but is not checked by the race detector.
+// This is necessary when implementing gopark callbacks, since no race context
+// is available during their execution.
+func RaceUncheckedAtomicCompareAndSwapUintptr(ptr *uintptr, old, new uintptr) bool
diff --git a/pkg/sync/runtime_unsafe.go b/pkg/sync/runtime_unsafe.go
new file mode 100644
index 000000000..7ad6a4434
--- /dev/null
+++ b/pkg/sync/runtime_unsafe.go
@@ -0,0 +1,76 @@
+// 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.
+
+// +build go1.13
+// +build !go1.17
+
+// Check function signatures and constants when updating Go version.
+
+package sync
+
+import (
+	"unsafe"
+)
+
+// Note that go:linkname silently doesn't work if the local name is exported,
+// necessitating an indirection for exported functions.
+
+// Memmove is runtime.memmove, exported for SeqAtomicLoad/SeqAtomicTryLoad<T>.
+//
+//go:nosplit
+func Memmove(to, from unsafe.Pointer, n uintptr) {
+	memmove(to, from, n)
+}
+
+//go:linkname memmove runtime.memmove
+//go:noescape
+func memmove(to, from unsafe.Pointer, n uintptr)
+
+// Gopark is runtime.gopark. Gopark calls unlockf(pointer to runtime.g, lock);
+// if unlockf returns true, Gopark blocks until Goready(pointer to runtime.g)
+// is called. unlockf and its callees must be nosplit and norace, since stack
+// splitting and race context are not available where it is called.
+//
+//go:nosplit
+func Gopark(unlockf func(uintptr, unsafe.Pointer) bool, lock unsafe.Pointer, reason uint8, traceEv byte, traceskip int) {
+	gopark(unlockf, lock, reason, traceEv, traceskip)
+}
+
+//go:linkname gopark runtime.gopark
+func gopark(unlockf func(uintptr, unsafe.Pointer) bool, lock unsafe.Pointer, reason uint8, traceEv byte, traceskip int)
+
+// Goready is runtime.goready.
+//
+//go:nosplit
+func Goready(gp uintptr, traceskip int) {
+	goready(gp, traceskip)
+}
+
+//go:linkname goready runtime.goready
+func goready(gp uintptr, traceskip int)
+
+// Values for the reason argument to gopark, from Go's src/runtime/runtime2.go.
+const (
+	WaitReasonSelect uint8 = 9
+)
+
+// Values for the traceEv argument to gopark, from Go's src/runtime/trace.go.
+const (
+	TraceEvGoBlockSelect byte = 24
+)
+
+// These functions are only used within the sync package.
+
+//go:linkname semacquire sync.runtime_Semacquire
+func semacquire(s *uint32)
+
+//go:linkname semrelease sync.runtime_Semrelease
+func semrelease(s *uint32, handoff bool, skipframes int)
+
+//go:linkname canSpin sync.runtime_canSpin
+func canSpin(i int) bool
+
+//go:linkname doSpin sync.runtime_doSpin
+func doSpin()
diff --git a/pkg/sync/rwmutex_unsafe.go b/pkg/sync/rwmutex_unsafe.go
index fa023f5bb..dacd7772c 100644
--- a/pkg/sync/rwmutex_unsafe.go
+++ b/pkg/sync/rwmutex_unsafe.go
@@ -3,11 +3,6 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build go1.13
-// +build !go1.17
-
-// 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:
@@ -23,16 +18,10 @@ import (
 	"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)
-
 // RWMutex is identical to sync.RWMutex, but adds the DowngradeLock,
 // TryLock and TryRLock methods.
 type RWMutex struct {
-	// w is held if there are pending writers
+	// w is held by writers.
 	//
 	// We use CrossGoroutineMutex rather than Mutex because the lock
 	// annotation instrumentation in Mutex will trigger false positives in
@@ -78,7 +67,7 @@ func (rw *RWMutex) RLock() {
 	}
 	if atomic.AddInt32(&rw.readerCount, 1) < 0 {
 		// A writer is pending, wait for it.
-		runtimeSemacquire(&rw.readerSem)
+		semacquire(&rw.readerSem)
 	}
 	if RaceEnabled {
 		RaceEnable()
@@ -99,7 +88,7 @@ func (rw *RWMutex) RUnlock() {
 		// A writer is pending.
 		if atomic.AddInt32(&rw.readerWait, -1) == 0 {
 			// The last reader unblocks the writer.
-			runtimeSemrelease(&rw.writerSem, false, 0)
+			semrelease(&rw.writerSem, false, 0)
 		}
 	}
 	if RaceEnabled {
@@ -146,7 +135,7 @@ func (rw *RWMutex) Lock() {
 	r := atomic.AddInt32(&rw.readerCount, -rwmutexMaxReaders) + rwmutexMaxReaders
 	// Wait for active readers.
 	if r != 0 && atomic.AddInt32(&rw.readerWait, r) != 0 {
-		runtimeSemacquire(&rw.writerSem)
+		semacquire(&rw.writerSem)
 	}
 	if RaceEnabled {
 		RaceEnable()
@@ -168,7 +157,7 @@ func (rw *RWMutex) Unlock() {
 	}
 	// Unblock blocked readers, if any.
 	for i := 0; i < int(r); i++ {
-		runtimeSemrelease(&rw.readerSem, false, 0)
+		semrelease(&rw.readerSem, false, 0)
 	}
 	// Allow other writers to proceed.
 	rw.w.Unlock()
@@ -191,7 +180,7 @@ func (rw *RWMutex) DowngradeLock() {
 	// 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)
+		semrelease(&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