cpython/Include/internal/pycore_gil.h

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#ifndef Py_INTERNAL_GIL_H
#define Py_INTERNAL_GIL_H
#ifdef __cplusplus
extern "C" {
#endif
#ifndef Py_BUILD_CORE
# error "this header requires Py_BUILD_CORE define"
#endif
#include "pycore_condvar.h" // PyCOND_T
#ifndef Py_HAVE_CONDVAR
# error You need either a POSIX-compatible or a Windows system!
#endif
/* Enable if you want to force the switching of threads at least
every `interval`. */
#undef FORCE_SWITCHING
#define FORCE_SWITCHING
struct _gil_runtime_state {
#ifdef Py_GIL_DISABLED
/* If this GIL is disabled, enabled == 0.
If this GIL is enabled transiently (most likely to initialize a module
of unknown safety), enabled indicates the number of active transient
requests.
If this GIL is enabled permanently, enabled == INT_MAX.
It must not be modified directly; use _PyEval_EnableGILTransiently(),
_PyEval_EnableGILPermanently(), and _PyEval_DisableGIL()
It is always read and written atomically, but a thread can assume its
value will be stable as long as that thread is attached or knows that no
other threads are attached (e.g., during a stop-the-world.). */
int enabled;
#endif
/* microseconds (the Python API uses seconds, though) */
unsigned long interval;
/* Last PyThreadState holding / having held the GIL. This helps us
know whether anyone else was scheduled after we dropped the GIL. */
PyThreadState* last_holder;
/* Whether the GIL is already taken (-1 if uninitialized). This is
atomic because it can be read without any lock taken in ceval.c. */
int locked;
/* Number of GIL switches since the beginning. */
unsigned long switch_number;
/* This condition variable allows one or several threads to wait
until the GIL is released. In addition, the mutex also protects
the above variables. */
PyCOND_T cond;
PyMUTEX_T mutex;
#ifdef FORCE_SWITCHING
/* This condition variable helps the GIL-releasing thread wait for
a GIL-awaiting thread to be scheduled and take the GIL. */
PyCOND_T switch_cond;
PyMUTEX_T switch_mutex;
#endif
};
#ifdef __cplusplus
}
#endif
#endif /* !Py_INTERNAL_GIL_H */