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))
}