https://github.com/python/cpython/commit/b4ff8b22b3066b814c3758f87eaddfa923e657ed
commit: b4ff8b22b3066b814c3758f87eaddfa923e657ed
branch: main
author: Peter Hawkins <[email protected]>
committer: colesbury <[email protected]>
date: 2025-02-06T18:49:29Z
summary:
gh-129732: Fix race on `shared->array` in qsbr code under free-threading
(gh-129738)
The read of `shared->array` should happen under the lock to avoid a race.
files:
A
Misc/NEWS.d/next/Core_and_Builtins/2025-02-06-17-57-33.gh-issue-129732.yl97oq.rst
M Python/qsbr.c
diff --git
a/Misc/NEWS.d/next/Core_and_Builtins/2025-02-06-17-57-33.gh-issue-129732.yl97oq.rst
b/Misc/NEWS.d/next/Core_and_Builtins/2025-02-06-17-57-33.gh-issue-129732.yl97oq.rst
new file mode 100644
index 00000000000000..a4b104af61692a
--- /dev/null
+++
b/Misc/NEWS.d/next/Core_and_Builtins/2025-02-06-17-57-33.gh-issue-129732.yl97oq.rst
@@ -0,0 +1 @@
+Fixed a race in ``_Py_qsbr_reserve`` in the free threading build.
diff --git a/Python/qsbr.c b/Python/qsbr.c
index a40219acfe2c29..0df1285cc8e063 100644
--- a/Python/qsbr.c
+++ b/Python/qsbr.c
@@ -205,15 +205,15 @@ _Py_qsbr_reserve(PyInterpreterState *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
// 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
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