如果到超时时间段结束时还没有被唤醒，读线程需要唤醒自身并释放互斥锁。

If not awake otherwise, at the end of the timeout, the reader needs to wake itself up and release the mutex.

youdao

虽然旋转锁是cpu密集型的，显得效率低下，但是如果争夺的锁被持有的时间非常短，那么旋转锁要比暂挂线程然后再唤醒它更有效率。

While spin locks are CPU-intensive and appear inefficient, they can be more efficient than suspending the thread and subsequently waking it up if the lock in question is held for a very short time.

youdao

当拥有锁的线程离开临界区的时候，挂起的线程需要被重新唤醒，然后重新被调用，并交换上下文，回到CPU调度中。

When the thread that has the lock leaves the critical section, the suspended thread needs to be woken up. The thread will need to be re-scheduling and context switched back into the CPU.

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