15.7 从C扩展中释放全局锁

## 问题 You have C extension code in that you want to execute concurrently with other threadsin the Python interpreter. To do this, you need to release and reacquire the global in‐terpreter lock (GIL). ## 解决方案 In C extension code, the GIL can be released and reacquired by inserting the followingmacros in the code: #include “Python.h”... PyObject [*](#)pyfunc(PyObject [*](#)self, PyObject [*](#)args) {...Py_BEGIN_ALLOW_THREADS// Threaded C code. Must not use Python API functions...Py_END_ALLOW_THREADS...return result; } ## 讨论 The GIL can only safely be released if you can guarantee that no Python C API functionswill be executed in the C code. Typical examples where the GIL might be released arein computationally intensive code that performs calculations on C arrays (e.g., in ex‐tensions such as numpy) or in code where blocking I/O operations are going to be per‐formed (e.g., reading or writing on a file descriptor).While the GIL is released, other Python threads are allowed to execute in the interpreter.The Py_END_ALLOW_THREADS macro blocks execution until the calling threads reacquiresthe GIL in the interpreter.