// Unlock 为 rw 的写入将其解锁。
// 若 rw 并没有为写入而锁定，调用 Unlock 就会引发一个运行时错误。
//
// 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.
// 正如 Mutex 一样，已锁定的 RWMutex 并不与特定的Go程相关联。一个Go程可
// RLock（Lock）一个 RWMutex，然后安排其它Go程来 RUnlock（Unlock）它。
func (rw *RWMutex) Unlock() {
if race.Enabled {
_ = rw.w.state
race.Release(unsafe.Pointer(&rw.readerSem))
race.Release(unsafe.Pointer(&rw.writerSem))
race.Disable()
}
// Announce to readers there is no active writer.
// 通知读取器现在没有活动的写入器。
r := atomic.AddInt32(&rw.readerCount, rwmutexMaxReaders)
if r >= rwmutexMaxReaders {
race.Enable()
panic("sync: Unlock of unlocked RWMutex")
}
// Unblock blocked readers, if any.
// 若有，就 Unblock 已锁定的读取器。
for i := 0; i < int(r); i++ {
runtime_Semrelease(&rw.readerSem)
}
// Allow other writers to proceed.
// 允许其它写入器继续。
rw.w.Unlock()
if race.Enabled {
race.Enable()
}
}
// Unlock unlocks m.
// It is a run-time error if m is not locked on entry to Unlock.
//
// A locked Mutex is not associated with a particular goroutine.
// It is allowed for one goroutine to lock a Mutex and then
// arrange for another goroutine to unlock it.
func (m *Mutex) Unlock() {
if race.Enabled {
_ = m.state
race.Release(unsafe.Pointer(m))
}
// Fast path: drop lock bit.
new := atomic.AddInt32(&m.state, -mutexLocked)
if (new+mutexLocked)&mutexLocked == 0 {
panic("sync: unlock of unlocked mutex")
}
old := new
for {
// If there are no waiters or a goroutine has already
// been woken or grabbed the lock, no need to wake anyone.
if old>>mutexWaiterShift == 0 || old&(mutexLocked|mutexWoken) != 0 {
return
}
// Grab the right to wake someone.
new = (old - 1<<mutexWaiterShift) | mutexWoken
if atomic.CompareAndSwapInt32(&m.state, old, new) {
runtime_Semrelease(&m.sema)
return
}
old = m.state
}
}
// Unlock unlocks rw for writing. It is a run-time error if rw is
// not locked for writing on entry to Unlock.
//
// 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() {
if race.Enabled {
_ = rw.w.state
race.Release(unsafe.Pointer(&rw.readerSem))
race.Release(unsafe.Pointer(&rw.writerSem))
race.Disable()
}
// Announce to readers there is no active writer.
r := atomic.AddInt32(&rw.readerCount, rwmutexMaxReaders)
if r >= rwmutexMaxReaders {
race.Enable()
throw("sync: Unlock of unlocked RWMutex")
}
// Unblock blocked readers, if any.
for i := 0; i < int(r); i++ {
runtime_Semrelease(&rw.readerSem)
}
// Allow other writers to proceed.
rw.w.Unlock()
if race.Enabled {
race.Enable()
}
}