gh-146536: docs: Clarify that PyMutex is not re-entrant#146543
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dagangtj wants to merge 1 commit intopython:mainfrom
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gh-146536: docs: Clarify that PyMutex is not re-entrant#146543dagangtj wants to merge 1 commit intopython:mainfrom
dagangtj wants to merge 1 commit intopython:mainfrom
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Add explicit documentation that PyMutex is not re-entrant (recursive): - Add note to PyMutex type explaining it will deadlock on re-entry - Add warning to PyMutex_Lock about deadlock if already held - Clarify PyMutex_Unlock must be called by the locking thread Fixes python#146536
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Summary
This PR clarifies the documentation for :c:type:
PyMutexto explicitly state that it is not re-entrant (recursive).Changes
PyMutextype documentation explaining that it will deadlock if a thread attempts to acquire a lock it already holdsPyMutex_Lockabout deadlock behavior on re-entryPyMutex_Unlockmust be called by the same thread that acquired the lockBackground
The original issue reported confusion about whether PyMutex supports re-entrant locking. Since PyMutex occupies only one byte and uses atomic operations without tracking thread ownership, it cannot support re-entrancy. This documentation update makes this limitation explicit and suggests using :c:func:
Py_BEGIN_CRITICAL_SECTIONas an alternative for re-entrant locking scenarios.Fixes #146536
📚 Documentation preview 📚: https://cpython-previews--146543.org.readthedocs.build/