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