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gh-156910: fix deadlock in type_set_abstractmethods under free-threading #156948

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Merged
kumaraditya303 merged 2 commits into from
Sep 9, 2026
+6 −0
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gh-156910: fix deadlock in type_set_abstractmethods under free-threading #156948

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31e364a
fix deadlock in type_set_abstractmethods
kumaraditya303 Sep 4, 2026
eda5e81
add news
kumaraditya303 Sep 4, 2026
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3 changes: 3 additions & 0 deletions Misc/NEWS.d/next/Core_and_Builtins/2026-09-04-22-00-00.gh-issue-156910.aBcD3f.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,3 @@
Fix a deadlock in the :term:`free threaded <free threading>` build when
setting ``__abstractmethods__`` on a type while another thread holds the
type lock.
3 changes: 3 additions & 0 deletions Objects/typeobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1706,14 +1706,17 @@ type_set_abstractmethods(PyObject *tp, PyObject *value, void *Py_UNUSED(closure)
return -1;
}

pinned_mutexes_t pinned;
BEGIN_TYPE_LOCK();
_PyType_Modified_Unlocked(type);
type_lock_prevent_release(&pinned);
types_stop_world();
if (abstract)
type_add_flags(type, Py_TPFLAGS_IS_ABSTRACT);
else
type_clear_flags(type, Py_TPFLAGS_IS_ABSTRACT);
types_start_world();
type_lock_allow_release(&pinned);
ASSERT_TYPE_LOCK_HELD();
END_TYPE_LOCK();

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