Use standard library sync.Mutex.TryLock.

iangudger · iangudger · commit 288fcb821822 · 2022-10-15T23:55:24.000-07:00
The standard library sync.Mutex has included a TryLock method since Go 1.18. There is no longer a need to implement a parallel version with unsafe. Using the standard library version reduces the ongoing maintenance cost of this package. https://pkg.go.dev/sync#Mutex.TryLock https://tip.golang.org/doc/go1.18#minor_library_changes
diff --git a/.github/workflows/go.yml b/.github/workflows/go.yml
@@ -45,7 +45,7 @@ jobs:
         fetch-depth: 0
     - uses: actions/setup-go@v2
       with:
-        go-version: 1.17
+        go-version: 1.18
     - run: tools/go_branch.sh
     - run: git checkout go && git clean -xf . && go build ./...
     - if: github.event_name == 'push'
diff --git a/pkg/sync/BUILD b/pkg/sync/BUILD
@@ -42,7 +42,6 @@ go_test(
     size = "small",
     srcs = [
         "gate_test.go",
-        "mutex_test.go",
         "rwmutex_test.go",
         "seqcount_test.go",
     ],
diff --git a/pkg/sync/mutex_test.go b/pkg/sync/mutex_test.go
diff --git a/pkg/sync/mutex_unsafe.go b/pkg/sync/mutex_unsafe.go
@@ -3,62 +3,35 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build go1.13 && !go1.21
-// +build go1.13,!go1.21
-
-// When updating the build constraint (above), check that syncMutex matches the
-// standard library sync.Mutex definition.
-
 package sync
 
 import (
 	"sync"
-	"sync/atomic"
 	"unsafe"
 )
 
 // CrossGoroutineMutex is equivalent to Mutex, but it need not be unlocked by a
 // the same goroutine that locked the mutex.
 type CrossGoroutineMutex struct {
-	sync.Mutex
-}
-
-type syncMutex struct {
-	state int32
-	sema  uint32
-}
-
-func (m *CrossGoroutineMutex) state() *int32 {
-	return &(*syncMutex)(unsafe.Pointer(&m.Mutex)).state
+	m sync.Mutex
 }
 
 // Lock locks the underlying Mutex.
 // +checklocksignore
 func (m *CrossGoroutineMutex) Lock() {
-	m.Mutex.Lock()
+	m.m.Lock()
 }
 
 // Unlock unlocks the underlying Mutex.
 // +checklocksignore
 func (m *CrossGoroutineMutex) Unlock() {
-	m.Mutex.Unlock()
+	m.m.Unlock()
 }
 
-const (
-	mutexUnlocked = 0
-	mutexLocked   = 1
-)
-
 // TryLock tries to acquire the mutex. It returns true if it succeeds and false
 // otherwise. TryLock does not block.
 func (m *CrossGoroutineMutex) TryLock() bool {
-	if atomic.CompareAndSwapInt32(m.state(), mutexUnlocked, mutexLocked) {
-		if RaceEnabled {
-			RaceAcquire(unsafe.Pointer(&m.Mutex))
-		}
-		return true
-	}
-	return false
+	return m.m.TryLock()
 }
 
 // Mutex is a mutual exclusion lock. The zero value for a Mutex is an unlocked
