Consolidate most synchronization primitive linknames in the sync package.

PiperOrigin-RevId: 345359823

pkg/sleep/BUILD

@@ -5,10 +5,6 @@ package(licenses = ["notice"])
 go_library(
     name = "sleep",
     srcs = [
-        "commit_amd64.s",
-        "commit_arm64.s",
-        "commit_asm.go",
-        "commit_noasm.go",
         "sleep_unsafe.go",
     ],
     visibility = ["//:sandbox"],

pkg/sleep/commit_amd64.s

@@ -1,35 +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.
-
-#include "textflag.h"
-
-#define preparingG 1
-
-// See commit_noasm.go for a description of commitSleep.
-//
-// func commitSleep(g uintptr, waitingG *uintptr) bool
-TEXT ·commitSleep(SB),NOSPLIT,$0-24
-	MOVQ waitingG+8(FP), CX
-	MOVQ g+0(FP), DX
-
-	// Store the G in waitingG if it's still preparingG. If it's anything
-	// else it means a waker has aborted the sleep.
-	MOVQ $preparingG, AX
-	LOCK
-	CMPXCHGQ DX, 0(CX)
-
-	SETEQ AX
-	MOVB AX, ret+16(FP)
-
-	RET

pkg/sleep/commit_arm64.s

@@ -1,38 +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.
-
-#include "textflag.h"
-
-#define preparingG 1
-
-// See commit_noasm.go for a description of commitSleep.
-//
-// func commitSleep(g uintptr, waitingG *uintptr) bool
-TEXT ·commitSleep(SB),NOSPLIT,$0-24
-	MOVD waitingG+8(FP), R0
-	MOVD $preparingG, R1
-	MOVD G+0(FP), R2
-
-	// Store the G in waitingG if it's still preparingG. If it's anything
-	// else it means a waker has aborted the sleep.
-again:
-        LDAXR   (R0), R3
-        CMP     R1, R3
-        BNE     ok
-        STLXR   R2, (R0), R3
-        CBNZ    R3, again
-ok:
-        CSET    EQ, R0
-        MOVB    R0, ret+16(FP)
-        RET

pkg/sleep/commit_asm.go

@@ -1,20 +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.
-
-// +build amd64 arm64
-
-package sleep
-
-// See commit_noasm.go for a description of commitSleep.
-func commitSleep(g uintptr, waitingG *uintptr) bool

pkg/sleep/commit_noasm.go

@@ -1,33 +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.
-
-// +build !race
-// +build !amd64,!arm64
-
-package sleep
-
-import "sync/atomic"
-
-// commitSleep signals to wakers that the given g is now sleeping. Wakers can
-// then fetch it and wake it.
-//
-// The commit may fail if wakers have been asserted after our last check, in
-// which case they will have set s.waitingG to zero.
-//
-// It is written in assembly because it is called from g0, so it doesn't have
-// a race context.
-func commitSleep(g uintptr, waitingG *uintptr) bool {
-	// Try to store the G so that wakers know who to wake.
-	return atomic.CompareAndSwapUintptr(waitingG, preparingG, g)
-}

pkg/sleep/empty.s

@@ -1,15 +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.
-
-// Empty assembly file so empty func definitions work.

pkg/sleep/sleep_unsafe.go

@@ -12,11 +12,6 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-// +build go1.11
-// +build !go1.17
-
-// Check go:linkname function signatures when updating Go version.
-
 // Package sleep allows goroutines to efficiently sleep on multiple sources of
 // notifications (wakers). It offers O(1) complexity, which is different from
 // multi-channel selects which have O(n) complexity (where n is the number of
@@ -91,12 +86,6 @@ var (
 	assertedSleeper Sleeper
 )
 
-//go:linkname gopark runtime.gopark
-func gopark(unlockf func(uintptr, *uintptr) bool, wg *uintptr, reason uint8, traceEv byte, traceskip int)
-
-//go:linkname goready runtime.goready
-func goready(g uintptr, traceskip int)
-
 // Sleeper allows a goroutine to sleep and receive wake up notifications from
 // Wakers in an efficient way.
 //
@@ -189,7 +178,7 @@ func (s *Sleeper) nextWaker(block bool) *Waker {
 			// See:runtime2.go in the go runtime package for
 			// the values to pass as the waitReason here.
 			const waitReasonSelect = 9
-			gopark(commitSleep, &s.waitingG, waitReasonSelect, traceEvGoBlockSelect, 0)
+			sync.Gopark(commitSleep, unsafe.Pointer(&s.waitingG), sync.WaitReasonSelect, sync.TraceEvGoBlockSelect, 0)
 		}
 
 		// Pull the shared list out and reverse it in the local
@@ -212,6 +201,18 @@ func (s *Sleeper) nextWaker(block bool) *Waker {
 	return w
 }
 
+// commitSleep signals to wakers that the given g is now sleeping. Wakers can
+// then fetch it and wake it.
+//
+// The commit may fail if wakers have been asserted after our last check, in
+// which case they will have set s.waitingG to zero.
+//
+//go:norace
+//go:nosplit
+func commitSleep(g uintptr, waitingG unsafe.Pointer) bool {
+	return sync.RaceUncheckedAtomicCompareAndSwapUintptr((*uintptr)(waitingG), preparingG, g)
+}
+
 // Fetch fetches the next wake-up notification. If a notification is immediately
 // available, it is returned right away. Otherwise, the behavior depends on the
 // value of 'block': if true, the current goroutine blocks until a notification
@@ -311,7 +312,7 @@ func (s *Sleeper) enqueueAssertedWaker(w *Waker) {
 	case 0, preparingG:
 	default:
 		// We managed to get a G. Wake it up.
-		goready(g, 0)
+		sync.Goready(g, 0)
 	}
 }
 

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,

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()

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()

pkg/sync/memmove_unsafe.go

@@ -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)
-}

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)
+}

pkg/sync/race_amd64.s

@@ -12,21 +12,22 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+// +build race
+// +build amd64
+
 #include "textflag.h"
 
-// See waiter_noasm_unsafe.go for a description of waiterUnlock.
-//
-// func waiterUnlock(ptr unsafe.Pointer, wg *unsafe.Pointer) bool
-TEXT ·waiterUnlock(SB),NOSPLIT,$0-24
+// func RaceUncheckedAtomicCompareAndSwapUintptr(ptr *uintptr, old, new uintptr) bool
+TEXT ·RaceUncheckedAtomicCompareAndSwapUintptr(SB),NOSPLIT,$0-25
 	MOVQ ptr+0(FP), DI
-	MOVQ wg+8(FP), SI
+	MOVQ old+8(FP), AX
+	MOVQ new+16(FP), SI
 
-	MOVQ $·preparingG(SB), AX
 	LOCK
-	CMPXCHGQ DI, 0(SI)
+	CMPXCHGQ SI, 0(DI)
 
 	SETEQ AX
-	MOVB AX, ret+16(FP)
+	MOVB AX, ret+24(FP)
 
 	RET
 

pkg/sync/race_arm64.s

@@ -12,15 +12,16 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+// +build race
+// +build arm64
+
 #include "textflag.h"
 
-// See waiter_noasm_unsafe.go for a description of waiterUnlock.
-//
-// func waiterUnlock(ptr unsafe.Pointer, wg *unsafe.Pointer) bool
-TEXT ·waiterUnlock(SB),NOSPLIT,$0-24
-	MOVD wg+8(FP), R0
-	MOVD $·preparingG(SB), R1
-	MOVD ptr+0(FP), R2
+// 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
@@ -29,6 +30,6 @@ again:
 	CBNZ R3, again
 ok:
 	CSET EQ, R0
-	MOVB R0, ret+16(FP)
+	MOVB R0, ret+24(FP)
 	RET
 

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

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()

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

pkg/syncevent/BUILD

@@ -9,10 +9,6 @@ go_library(
         "receiver.go",
         "source.go",
         "syncevent.go",
-        "waiter_amd64.s",
-        "waiter_arm64.s",
-        "waiter_asm_unsafe.go",
-        "waiter_noasm_unsafe.go",
         "waiter_unsafe.go",
     ],
     visibility = ["//:sandbox"],

pkg/syncevent/waiter_asm_unsafe.go

@@ -1,24 +0,0 @@
-// 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 amd64 arm64
-
-package syncevent
-
-import (
-	"unsafe"
-)
-
-// See waiter_noasm_unsafe.go for a description of waiterUnlock.
-func waiterUnlock(ptr unsafe.Pointer, wg *unsafe.Pointer) bool

pkg/syncevent/waiter_noasm_unsafe.go

@@ -1,39 +0,0 @@
-// 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.
-
-// waiterUnlock is called from g0, so when the race detector is enabled,
-// waiterUnlock must be implemented in assembly since no race context is
-// available.
-//
-// +build !race
-// +build !amd64,!arm64
-
-package syncevent
-
-import (
-	"sync/atomic"
-	"unsafe"
-)
-
-// waiterUnlock is the "unlock function" passed to runtime.gopark by
-// Waiter.Wait*. wg is &Waiter.g, and g is a pointer to the calling runtime.g.
-// waiterUnlock returns true if Waiter.Wait should sleep and false if sleeping
-// should be aborted.
-//
-//go:nosplit
-func waiterUnlock(ptr unsafe.Pointer, wg *unsafe.Pointer) bool {
-	// The only way this CAS can fail is if a call to Waiter.NotifyPending()
-	// has replaced *wg with nil, in which case we should not sleep.
-	return atomic.CompareAndSwapPointer(wg, (unsafe.Pointer)(&preparingG), ptr)
-}