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bpo-39877: 4th take_gil() fix for daemon threads #19080

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Merged
merged 1 commit into from
Mar 19, 2020
Merged

bpo-39877: 4th take_gil() fix for daemon threads #19080

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45 changes: 23 additions & 22 deletions Python/ceval_gil.h
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Original file line number Diff line number Diff line change
Expand Up @@ -196,8 +196,7 @@ tstate_must_exit(PyThreadState *tstate)
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);
PyThreadState *finalizing = _PyRuntimeState_GetFinalizing(&_PyRuntime);
return (finalizing != NULL && finalizing != tstate);
}

Expand Down Expand Up @@ -243,20 +242,23 @@ take_gil(PyThreadState *tstate)
}

while (_Py_atomic_load_relaxed(&gil->locked)) {
int timed_out = 0;
unsigned long saved_switchnum;

saved_switchnum = gil->switch_number;

unsigned long saved_switchnum = gil->switch_number;

unsigned long interval = (gil->interval >= 1 ? gil->interval : 1);
int timed_out = 0;
COND_TIMED_WAIT(gil->cond, gil->mutex, interval, timed_out);

/* If we timed out and no switch occurred in the meantime, it is time
to ask the GIL-holding thread to drop it. */
if (timed_out &&
_Py_atomic_load_relaxed(&gil->locked) &&
gil->switch_number == saved_switchnum)
{
if (tstate_must_exit(tstate)) {
MUTEX_UNLOCK(gil->mutex);
PyThread_exit_thread();
}

SET_GIL_DROP_REQUEST(ceval);
}
}
Expand All @@ -281,6 +283,19 @@ take_gil(PyThreadState *tstate)
MUTEX_UNLOCK(gil->switch_mutex);
#endif

if (tstate_must_exit(tstate)) {
/* bpo-36475: If Py_Finalize() has been called and tstate is not
the thread which called Py_Finalize(), exit immediately the
thread.

This code path can be reached by a daemon thread which was waiting
in take_gil() while the main thread called
wait_for_thread_shutdown() from Py_Finalize(). */
MUTEX_UNLOCK(gil->mutex);
drop_gil(ceval, ceval2, tstate);
PyThread_exit_thread();
}

if (_Py_atomic_load_relaxed(&ceval->gil_drop_request)) {
RESET_GIL_DROP_REQUEST(ceval, ceval2);
}
Expand All @@ -293,27 +308,13 @@ take_gil(PyThreadState *tstate)
COMPUTE_EVAL_BREAKER(ceval, ceval2);
}

int must_exit = tstate_must_exit(tstate);

/* Don't access tstate if the thread must exit */
if (!must_exit && tstate->async_exc != NULL) {
if (tstate->async_exc != NULL) {
_PyEval_SignalAsyncExc(tstate);
}

MUTEX_UNLOCK(gil->mutex);

if (must_exit) {
/* bpo-36475: If Py_Finalize() has been called and tstate is not
the thread which called Py_Finalize(), exit immediately the
thread.

This code path can be reached by a daemon thread which was waiting
in take_gil() while the main thread called
wait_for_thread_shutdown() from Py_Finalize(). */
drop_gil(ceval, ceval2, tstate);
PyThread_exit_thread();
}

errno = err;
}

Expand Down