操作系统OS，Python

参考：

1. https://stackoverflow.com/questions/49859287/what-is-the-need-of-threading-lock-when-cpython-has-gil
2. https://stackoverflow.com/questions/40072873/why-do-we-need-locks-for-threads-if-we-have-gil
3. https://en.wikipedia.org/wiki/Global_interpreter_lock
4. https://www.zhihu.com/question/23030421/answer/93789486 **通俗解释
5. https://softwareengineering.stackexchange.com/questions/186889/why-was-python-written-with-the-gil

1. 问题：在CPython中，既然有了GIL，为什么还要lock?

2. 答案：GIL保证了在同一时刻只能有一个线程运行，而lock保证共享数据的安全。lock实现了当某个线程进入临界区时，其他线程必须等待。