diff options
Diffstat (limited to 'libgo/go/sync/rwmutex.go')
-rw-r--r-- | libgo/go/sync/rwmutex.go | 59 |
1 files changed, 59 insertions, 0 deletions
diff --git a/libgo/go/sync/rwmutex.go b/libgo/go/sync/rwmutex.go index 3012b5548e4..f0d4c9771a0 100644 --- a/libgo/go/sync/rwmutex.go +++ b/libgo/go/sync/rwmutex.go @@ -68,6 +68,34 @@ func (rw *RWMutex) RLock() { } } +// TryRLock tries to lock rw for reading and reports whether it succeeded. +// +// Note that while correct uses of TryRLock do exist, they are rare, +// and use of TryRLock is often a sign of a deeper problem +// in a particular use of mutexes. +func (rw *RWMutex) TryRLock() bool { + if race.Enabled { + _ = rw.w.state + race.Disable() + } + for { + c := atomic.LoadInt32(&rw.readerCount) + if c < 0 { + if race.Enabled { + race.Enable() + } + return false + } + if atomic.CompareAndSwapInt32(&rw.readerCount, c, c+1) { + if race.Enabled { + race.Enable() + race.Acquire(unsafe.Pointer(&rw.readerSem)) + } + return true + } + } +} + // RUnlock undoes a single RLock call; // it does not affect other simultaneous readers. // It is a run-time error if rw is not locked for reading @@ -122,6 +150,37 @@ func (rw *RWMutex) Lock() { } } +// TryLock tries to lock rw for writing and reports whether it succeeded. +// +// Note that while correct uses of TryLock do exist, they are rare, +// and use of TryLock is often a sign of a deeper problem +// in a particular use of mutexes. +func (rw *RWMutex) TryLock() bool { + if race.Enabled { + _ = rw.w.state + race.Disable() + } + if !rw.w.TryLock() { + if race.Enabled { + race.Enable() + } + return false + } + if !atomic.CompareAndSwapInt32(&rw.readerCount, 0, -rwmutexMaxReaders) { + rw.w.Unlock() + if race.Enabled { + race.Enable() + } + return false + } + if race.Enabled { + race.Enable() + race.Acquire(unsafe.Pointer(&rw.readerSem)) + race.Acquire(unsafe.Pointer(&rw.writerSem)) + } + return true +} + // Unlock unlocks rw for writing. It is a run-time error if rw is // not locked for writing on entry to Unlock. // |