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[3.13] gh-127582: Make object resurrection thread-safe for free threading. (GH-127612) (GH-127659)

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Objects may be temporarily "resurrected" in destructors when calling
finalizers or watcher callbacks. We previously undid the resurrection
by decrementing the reference count using `Py_SET_REFCNT`. This was not
thread-safe because other threads might be accessing the object
(modifying its reference count) if it was exposed by the finalizer,
watcher callback, or temporarily accessed by a racy dictionary or list
access.

This adds internal-only thread-safe functions for temporary object
resurrection during destructors.
(cherry picked from commit f4f530804b)
This commit is contained in:
Sam Gross 2024-12-05 23:49:33 +00:00 • committed by GitHub
parent 304111e967
commit 69bb1c6c41
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GPG key ID: B5690EEEBB952194
6 changed files with 87 additions and 20 deletions
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7
Objects/codeobject.c
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@ -1845,14 +1845,11 @@ free_monitoring_data(_PyCoMonitoringData *data)
static void
code_dealloc(PyCodeObject *co)
{
assert(Py_REFCNT(co) == 0);
Py_SET_REFCNT(co, 1);
_PyObject_ResurrectStart((PyObject *)co);
notify_code_watchers(PY_CODE_EVENT_DESTROY, co);
if (Py_REFCNT(co) > 1) {
Py_SET_REFCNT(co, Py_REFCNT(co) - 1);
if (_PyObject_ResurrectEnd((PyObject *)co)) {
return;
}
Py_SET_REFCNT(co, 0);
#ifdef Py_GIL_DISABLED
PyObject_GC_UnTrack(co);