#ifndef Py_CPYTHON_LOCK_H # error "this header file must not be included directly" #endif #define _Py_UNLOCKED 0 #define _Py_LOCKED 1 // A mutex that occupies one byte. The lock can be zero initialized to // represent the unlocked state. // // Typical initialization: // PyMutex m = (PyMutex){0}; // // Or initialize as global variables: // static PyMutex m; // // Typical usage: // PyMutex_Lock(&m); // ... // PyMutex_Unlock(&m); // // The contents of the PyMutex are not part of the public API, but are // described to aid in understanding the implementation and debugging. Only // the two least significant bits are used. The remaining bits are always zero: // 0b00: unlocked // 0b01: locked // 0b10: unlocked and has parked threads // 0b11: locked and has parked threads typedef struct PyMutex { uint8_t _bits; // (private) } PyMutex; // exported function for locking the mutex PyAPI_FUNC(void) PyMutex_Lock(PyMutex *m); // exported function for unlocking the mutex PyAPI_FUNC(void) PyMutex_Unlock(PyMutex *m); // Locks the mutex. // // If the mutex is currently locked, the calling thread will be parked until // the mutex is unlocked. If the current thread holds the GIL, then the GIL // will be released while the thread is parked. static inline void _PyMutex_Lock(PyMutex *m) { uint8_t expected = _Py_UNLOCKED; if (!_Py_atomic_compare_exchange_uint8(&m->_bits, &expected, _Py_LOCKED)) { PyMutex_Lock(m); } } #define PyMutex_Lock _PyMutex_Lock // Unlocks the mutex. static inline void _PyMutex_Unlock(PyMutex *m) { uint8_t expected = _Py_LOCKED; if (!_Py_atomic_compare_exchange_uint8(&m->_bits, &expected, _Py_UNLOCKED)) { PyMutex_Unlock(m); } } #define PyMutex_Unlock _PyMutex_Unlock