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Diffstat (limited to 'Include/cpython/lock.h')
-rw-r--r-- | Include/cpython/lock.h | 63 |
1 files changed, 63 insertions, 0 deletions
diff --git a/Include/cpython/lock.h b/Include/cpython/lock.h new file mode 100644 index 0000000..8ee03e8 --- /dev/null +++ b/Include/cpython/lock.h @@ -0,0 +1,63 @@ +#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 |