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gh-158090: Fix hang at shutdown when a daemon thread resets the GIL drop request #158101

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gh-158090: Fix hang at shutdown when a daemon thread resets the GIL drop request #158101

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gh-158090: Fix hang at shutdown when a daemon thread resets the GIL d… 
…rop request
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@lazerg
lazerg committed Sep 24, 2026
commit 145cf80b799f1ecd67e00e11f214ec649148b01d
2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Core_and_Builtins/2026-09-24-14-57-33.gh-issue-158090.0jWUTp.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
Fix a race condition at interpreter shutdown where a daemon thread waiting
for the GIL could leave the main thread blocked forever in ``drop_gil()``.
2 changes: 1 addition & 1 deletion Python/ceval_gil.c
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Expand Up @@ -343,7 +343,6 @@ take_gil(PyThreadState *tstate)
PyThreadState *holder_tstate =
(PyThreadState*)_Py_atomic_load_ptr_relaxed(&gil->last_holder);
if (_PyThreadState_MustExit(tstate)) {
MUTEX_UNLOCK(gil->mutex);
// gh-96387: If the loop requested a drop request in a previous
// iteration, reset the request. Otherwise, drop_gil() can
// block forever waiting for the thread which exited. Drop
Expand All @@ -353,6 +352,7 @@ take_gil(PyThreadState *tstate)
if (drop_requested) {
_Py_unset_eval_breaker_bit(holder_tstate, _PY_GIL_DROP_REQUEST_BIT);
}
MUTEX_UNLOCK(gil->mutex);
// gh-87135: hang the thread as *thread_exit() is not a safe
// API. It lacks stack unwind and local variable destruction.
_PyThreadState_HangThread(tstate);
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