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gh-118727: Don't drop the GIL in drop_gil() unless the current thread holds it #118745

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Merged
merged 10 commits into from
May 23, 2024
Merged

gh-118727: Don't drop the GIL in drop_gil() unless the current thread holds it #118745

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1d21956
Don't drop the GIL during thread deletion unless the current thread h…
swtaarrs May 7, 2024
b91a1d5
Store holds_gil flag on PyThreadState instead, and use it where appro…
swtaarrs May 8, 2024
402ab90
Merge remote-tracking branch 'upstream/main' into cpython-drop-gil
swtaarrs May 8, 2024
29c853d
Account for tstate == NULL case
swtaarrs May 8, 2024
694926f
Always track holds_gil, related cleanup
swtaarrs May 8, 2024
480c07d
Fix ASAN error, pull drop_gil_impl() back into drop_gil()
swtaarrs May 9, 2024
d28bf13
Rename thread_dying to final_release
swtaarrs May 9, 2024
43f64d7
Merge remote-tracking branch 'upstream/main' into cpython-drop-gil
swtaarrs May 9, 2024
d056a46
Restore drop_gil_impl(), clear GIL drop request when disabling GIL
swtaarrs May 13, 2024
f32a503
Merge remote-tracking branch 'upstream/main' into cpython-drop-gil
swtaarrs May 13, 2024
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Always track holds_gil, related cleanup
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@swtaarrs
swtaarrs committed May 8, 2024
commit 694926fac8fce7067260a967b8c93769277c2dce
4 changes: 0 additions & 4 deletions Include/cpython/pystate.h
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Original file line number Diff line number Diff line change
Expand Up @@ -83,12 +83,8 @@ struct _ts {
unsigned int bound_gilstate:1;
/* Currently in use (maybe holds the GIL). */
unsigned int active:1;
#ifdef Py_GIL_DISABLED
/* Currently holds the GIL. */
unsigned int holds_gil:1;
#else
unsigned int _unused:1;
#endif

/* various stages of finalization */
unsigned int finalizing:1;
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26 changes: 12 additions & 14 deletions Python/ceval_gil.c
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Expand Up @@ -211,11 +211,9 @@ drop_gil_impl(PyThreadState *tstate, struct _gil_runtime_state *gil)
MUTEX_LOCK(gil->mutex);
_Py_ANNOTATE_RWLOCK_RELEASED(&gil->locked, /*is_write=*/1);
_Py_atomic_store_int_relaxed(&gil->locked, 0);
#ifdef Py_GIL_DISABLED
if (tstate != NULL) {
tstate->_status.holds_gil = 0;
}
#endif
COND_SIGNAL(gil->cond);
MUTEX_UNLOCK(gil->mutex);
}
Expand Down Expand Up @@ -377,9 +375,7 @@ take_gil(PyThreadState *tstate)
MUTEX_LOCK(gil->switch_mutex);
#endif
/* We now hold the GIL */
#ifdef Py_GIL_DISABLED
tstate->_status.holds_gil = 1;
#endif
_Py_atomic_store_int_relaxed(&gil->locked, 1);
_Py_ANNOTATE_RWLOCK_ACQUIRED(&gil->locked, /*is_write=*/1);

Expand All @@ -402,6 +398,8 @@ take_gil(PyThreadState *tstate)
in take_gil() while the main thread called
wait_for_thread_shutdown() from Py_Finalize(). */
MUTEX_UNLOCK(gil->mutex);
/* tstate could be a dangling pointer, so don't pass it to
drop_gil(). */
drop_gil(interp, NULL, 1);
PyThread_exit_thread();
}
Expand Down Expand Up @@ -458,17 +456,17 @@ PyEval_ThreadsInitialized(void)
static inline int
current_thread_holds_gil(struct _gil_runtime_state *gil, PyThreadState *tstate)
{
if (((PyThreadState*)_Py_atomic_load_ptr_relaxed(&gil->last_holder)) != tstate) {
#ifdef Py_GIL_DISABLED
assert(!tstate->_status.holds_gil);
#endif
return 0;
}
int holds_gil = tstate->_status.holds_gil;

// holds_gil is the source of truth; check that last_holder and gil->locked
// are consistent with it.
int locked = _Py_atomic_load_int_relaxed(&gil->locked);
#ifdef Py_GIL_DISABLED
assert(!tstate->_status.holds_gil || locked);
#endif
return locked;
int is_last_holder =
((PyThreadState*)_Py_atomic_load_ptr_relaxed(&gil->last_holder)) == tstate;
assert(!holds_gil || locked);
assert(!holds_gil || is_last_holder);

return holds_gil;
}
#endif

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3 changes: 1 addition & 2 deletions Python/pystate.c
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Expand Up @@ -2070,12 +2070,11 @@ _PyThreadState_Attach(PyThreadState *tstate)
}

#ifdef Py_GIL_DISABLED
if (_PyEval_IsGILEnabled(tstate) != tstate->_status.holds_gil) {
if (_PyEval_IsGILEnabled(tstate) && !tstate->_status.holds_gil) {
// The GIL was enabled between our call to _PyEval_AcquireLock()
// and when we attached (the GIL can't go from enabled to disabled
// here because only a thread holding the GIL can disable
// it). Detach and try again.
assert(!tstate->_status.holds_gil);
tstate_set_detached(tstate, _Py_THREAD_DETACHED);
tstate_deactivate(tstate);
current_fast_clear(&_PyRuntime);
Expand Down