If the decrement leaves threadcount at zero, we know that there are no threads running, so it's time to exit.

如果互斥量threadcount的值减小到了零，我们知道这时已经没有线程在运行了，该退出程序了。

youdao

One way would be to increment a variable every time a thread is created, and decrement it whenever a thread terminates. When it reaches zero again, close the whole process.

一种解决方法是增加一个变量，每创建一个新的线程该变量就加1，每终止一个线程该变量就减1，当该变量再次为零时，就关闭整个进程。

youdao

If after the decrement it is zero, reset the lock to unlocked.

如果减少为零后，复位锁解锁。

youdao