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gh-129732: Fix race on shared->array in qsbr code under free-threading (gh-129738)

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The read of `shared->array` should happen under the lock to avoid a race.
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Peter Hawkins 2025-02-06 13:49:29 -05:00 • committed by GitHub
parent 78377c788e
commit b4ff8b22b3
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2 changed files with 7 additions and 6 deletions
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Misc/NEWS.d/next/Core_and_Builtins/2025-02-06-17-57-33.gh-issue-129732.yl97oq.rst Normal file
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@ -0,0 +1 @@
Fixed a race in ``_Py_qsbr_reserve`` in the free threading build.

12
Python/qsbr.c
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@ -205,15 +205,15 @@ _Py_qsbr_reserve(PyInterpreterState *interp)
} }
_PyEval_StartTheWorld(interp); _PyEval_StartTheWorld(interp);
} }
PyMutex_Unlock(&shared->mutex);
if (qsbr == NULL) {
return -1;
}
// Return an index rather than the pointer because the array may be // Return an index rather than the pointer because the array may be
// resized and the pointer invalidated. // resized and the pointer invalidated.
return (struct _qsbr_pad *)qsbr - shared->array; Py_ssize_t index = -1;
if (qsbr != NULL) {
index = (struct _qsbr_pad *)qsbr - shared->array;
}
PyMutex_Unlock(&shared->mutex);
return index;
} }
void void