1·When signal is received thread1 continues execution (after it reacquires the mutex).
当信号接收线程1继续执行(后重新获取互斥)。
2·Optionally exits the synchronization domain for the synchronized context before the wait and reacquires the domain afterward.
在等候之前和重新取得领域之后，可选择性地结束同步化内容的同步处理领域。