在src/sync/rwmutex.go文件中的implementions,我們可以看到的 「鎖定」 的定義如下:RWMutex.Lock()在golang
func (rw *RWMutex) Lock() {
if race.Enabled {
_ = rw.w.state
race.Disable()
}
// First, resolve competition with other writers.
rw.w.Lock()
// Announce to readers there is a pending writer.
r := atomic.AddInt32(&rw.readerCount, -rwmutexMaxReaders) + rwmutexMaxReaders
// Wait for active readers.
if r != 0 && atomic.AddInt32(&rw.readerWait, r) != 0 {
runtime_Semacquire(&rw.writerSem)
}
if race.Enabled {
race.Enable()
race.Acquire(unsafe.Pointer(&rw.readerSem))
race.Acquire(unsafe.Pointer(&rw.writerSem))
}
}
所以,我真的不知道什麼
atomic.AddInt32(&rw.readerCount, -rwmutexMaxReaders) + rwmutexMaxReaders
這句話手段。正如它所說,如何向讀者公佈?如何理解它?
rw.readerCount <= rwmutexMaxReaders,因此rw.readerCount-rwmutexMaxReaders使readerCount 0或negativ(信號)。加回rwmutxMaxReaders使r等於readerWait的實數。 – Volker