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bpo-39877: Refactor take_gil() function (GH-18885)

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* Remove ceval parameter of take_gil(): get it from tstate.
* Move exit_thread_if_finalizing() call inside take_gil(). Replace
  exit_thread_if_finalizing() with tstate_must_exit(): the caller is
  now responsible to call PyThread_exit_thread().
* Move is_tstate_valid() assertion inside take_gil(). Remove
  is_tstate_valid(): inline code into take_gil().
* Move gil_created() assertion inside take_gil().
This commit is contained in:
Victor Stinner 2020-03-09 22:12:04 +01:00 • committed by GitHub
parent 363fab83b8
commit 85f5a69ae1
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2 changed files with 53 additions and 66 deletions
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41
Python/ceval_gil.h
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@ -180,17 +180,55 @@ drop_gil(struct _ceval_runtime_state *ceval, PyThreadState *tstate)
#endif
}
/* Check if a Python thread must exit immediately, rather than taking the GIL
if Py_Finalize() has been called.
When this function is called by a daemon thread after Py_Finalize() has been
called, the GIL does no longer exist.
tstate must be non-NULL. */
static inline int
tstate_must_exit(PyThreadState *tstate)
{
/* bpo-39877: Access _PyRuntime directly rather than using
tstate->interp->runtime to support calls from Python daemon threads.
After Py_Finalize() has been called, tstate can be a dangling pointer:
point to PyThreadState freed memory. */
_PyRuntimeState *runtime = &_PyRuntime;
PyThreadState *finalizing = _PyRuntimeState_GetFinalizing(runtime);
return (finalizing != NULL && finalizing != tstate);
}
/* Take the GIL.
The function saves errno at entry and restores its value at exit.
tstate must be non-NULL. */
static void
take_gil(struct _ceval_runtime_state *ceval, PyThreadState *tstate)
take_gil(PyThreadState *tstate)
{
int err = errno;
assert(tstate != NULL);
/* Check if we should make a quick exit. */
if (tstate_must_exit(tstate)) {
PyThread_exit_thread();
}
/* Ensure that tstate is valid: sanity check for PyEval_AcquireThread() and
PyEval_RestoreThread(). Detect if tstate memory was freed. */
assert(!_PyMem_IsPtrFreed(tstate));
assert(!_PyMem_IsPtrFreed(tstate->interp));
struct _ceval_runtime_state *ceval = &tstate->interp->runtime->ceval;
struct _gil_runtime_state *gil = &ceval->gil;
/* Check that _PyEval_InitThreads() was called to create the lock */
assert(gil_created(gil));
MUTEX_LOCK(gil->mutex);
if (!_Py_atomic_load_relaxed(&gil->locked)) {
@ -215,6 +253,7 @@ take_gil(struct _ceval_runtime_state *ceval, PyThreadState *tstate)
SET_GIL_DROP_REQUEST(ceval);
}
}
_ready:
#ifdef FORCE_SWITCHING
/* This mutex must be taken before modifying gil->last_holder: