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gh-155400: Fix deadlock with type_lock_prevent_release() - #155401
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nascheme wants to merge 1 commit into
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gh-155400: Fix deadlock with type_lock_prevent_release()#155401nascheme wants to merge 1 commit into
nascheme wants to merge 1 commit into
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Two threads assigning to a special method of the same class could deadlock in the free-threaded build. If type_lock_prevent_release() only acts on TYPE_LOCK then we can get lock inversion. This happens when BEGIN_TYPE_DICT_LOCK() is used and the critical section holds both mutexes. We need to prevent release of both mutexes. Assisted-by: Claude
nascheme
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Aug 9, 2026
MemberAuthor
This PR requires GH-155370 to be merged first otherwise the unit test added exposes data-races. |
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Two threads assigning to a special method of the same class could deadlock in the free-threaded build. If type_lock_prevent_release() only acts on TYPE_LOCK then we can get lock inversion. This happens when BEGIN_TYPE_DICT_LOCK() is used and the critical section holds both mutexes. We need to prevent release of both mutexes.