diff options
Diffstat (limited to 'libgo/go/sync/rwmutex.go')
| -rw-r--r-- | libgo/go/sync/rwmutex.go | 33 |
1 files changed, 22 insertions, 11 deletions
diff --git a/libgo/go/sync/rwmutex.go b/libgo/go/sync/rwmutex.go index 06fd0b0ffb2..9248b4b0370 100644 --- a/libgo/go/sync/rwmutex.go +++ b/libgo/go/sync/rwmutex.go @@ -4,6 +4,8 @@ package sync +import "sync/atomic" + // An RWMutex is a reader/writer mutual exclusion lock. // The lock can be held by an arbitrary number of readers // or a single writer. @@ -14,9 +16,9 @@ package sync // Writers take priority over Readers: no new RLocks // are granted while a blocked Lock call is waiting. type RWMutex struct { - w Mutex // held if there are pending readers or writers - r Mutex // held if the w is being rd - readerCount uint32 // number of pending readers + w Mutex // held if there are pending readers or writers + r Mutex // held if the w is being rd + readerCount int32 // number of pending readers } // RLock locks rw for reading. @@ -33,7 +35,7 @@ func (rw *RWMutex) RLock() { // B: rw.RUnlock() // ... (new readers come and go indefinitely, W is starving) rw.r.Lock() - if xadd(&rw.readerCount, 1) == 1 { + if atomic.AddInt32(&rw.readerCount, 1) == 1 { // The first reader locks rw.w, so writers will be blocked // while the readers have the RLock. rw.w.Lock() @@ -46,7 +48,7 @@ func (rw *RWMutex) RLock() { // It is a run-time error if rw is not locked for reading // on entry to RUnlock. func (rw *RWMutex) RUnlock() { - if xadd(&rw.readerCount, -1) == 0 { + if atomic.AddInt32(&rw.readerCount, -1) == 0 { // last reader finished, enable writers rw.w.Unlock() } @@ -64,12 +66,21 @@ func (rw *RWMutex) Lock() { rw.r.Unlock() } -// Unlock unlocks rw for writing. -// It is a run-time error if rw is not locked for writing -// on entry to Unlock. +// Unlock unlocks rw for writing. It is a run-time error if rw is +// not locked for writing on entry to Unlock. // -// Like for Mutexes, -// a locked RWMutex is not associated with a particular goroutine. -// It is allowed for one goroutine to RLock (Lock) an RWMutex and then +// As with Mutexes, a locked RWMutex is not associated with a particular +// goroutine. One goroutine may RLock (Lock) an RWMutex and then // arrange for another goroutine to RUnlock (Unlock) it. func (rw *RWMutex) Unlock() { rw.w.Unlock() } + +// RLocker returns a Locker interface that implements +// the Lock and Unlock methods by calling rw.RLock and rw.RUnlock. +func (rw *RWMutex) RLocker() Locker { + return (*rlocker)(rw) +} + +type rlocker RWMutex + +func (r *rlocker) Lock() { (*RWMutex)(r).RLock() } +func (r *rlocker) Unlock() { (*RWMutex)(r).RUnlock() } |
