1 files changed, 46 insertions, 5 deletions
diff --git a/pkg/sync/mutex_unsafe.go b/pkg/sync/mutex_unsafe.go
index f4c2e9642..21084b857 100644
--- a/pkg/sync/mutex_unsafe.go
+++ b/pkg/sync/mutex_unsafe.go
@@ -17,8 +17,9 @@ import (
 	"unsafe"
 )
 
-// Mutex is a try lock.
-type Mutex struct {
+// 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
 }
 
@@ -27,7 +28,7 @@ type syncMutex struct {
 	sema  uint32
 }
 
-func (m *Mutex) state() *int32 {
+func (m *CrossGoroutineMutex) state() *int32 {
 	return &(*syncMutex)(unsafe.Pointer(&m.Mutex)).state
 }
 
@@ -36,9 +37,9 @@ const (
 	mutexLocked   = 1
 )
 
-// TryLock tries to aquire the mutex. It returns true if it succeeds and false
+// TryLock tries to acquire the mutex. It returns true if it succeeds and false
 // otherwise. TryLock does not block.
-func (m *Mutex) TryLock() bool {
+func (m *CrossGoroutineMutex) TryLock() bool {
 	if atomic.CompareAndSwapInt32(m.state(), mutexUnlocked, mutexLocked) {
 		if RaceEnabled {
 			RaceAcquire(unsafe.Pointer(&m.Mutex))
@@ -47,3 +48,43 @@ func (m *Mutex) TryLock() bool {
 	}
 	return false
 }
+
+// Mutex is a mutual exclusion lock. The zero value for a Mutex is an unlocked
+// mutex.
+//
+// A Mutex must not be copied after first use.
+//
+// A Mutex must be unlocked by the same goroutine that locked it. This
+// invariant is enforced with the 'checklocks' build tag.
+type Mutex struct {
+	m CrossGoroutineMutex
+}
+
+// Lock locks m. If the lock is already in use, the calling goroutine blocks
+// until the mutex is available.
+func (m *Mutex) Lock() {
+	noteLock(unsafe.Pointer(m))
+	m.m.Lock()
+}
+
+// Unlock unlocks m.
+//
+// Preconditions:
+// * m is locked.
+// * m was locked by this goroutine.
+func (m *Mutex) Unlock() {
+	noteUnlock(unsafe.Pointer(m))
+	m.m.Unlock()
+}
+
+// TryLock tries to acquire the mutex. It returns true if it succeeds and false
+// otherwise. TryLock does not block.
+func (m *Mutex) TryLock() bool {
+	// Note lock first to enforce proper locking even if unsuccessful.
+	noteLock(unsafe.Pointer(m))
+	locked := m.m.TryLock()
+	if !locked {
+		noteUnlock(unsafe.Pointer(m))
+	}
+	return locked
+}