https://github.com/python/cpython/commit/80d7626c74c1e455a9a2e0d34a06bf29b9970487 commit: 80d7626c74c1e455a9a2e0d34a06bf29b9970487 branch: 3.15 author: Miss Islington (bot) <[email protected]> committer: colesbury <[email protected]> date: 2026-06-19T09:52:07-04:00 summary:
[3.15] gh-150902: Optimize PyCriticalSection2 to skip locking the same locks held by the current CS2 (gh-151554) This mimics an optimization already present for the single-mutex critical section. (cherry picked from commit c2ca7724af94df6e078a4b2e86d1be8c410d9940) Co-authored-by: Daniele Parmeggiani <[email protected]> files: A Misc/NEWS.d/next/Core_and_Builtins/2026-06-08-13-14-42.gh-issue-150902.-CWZ66.rst M Include/internal/pycore_critical_section.h M Python/critical_section.c diff --git a/Include/internal/pycore_critical_section.h b/Include/internal/pycore_critical_section.h index 2a2846b1296b90..51d99d74ca159f 100644 --- a/Include/internal/pycore_critical_section.h +++ b/Include/internal/pycore_critical_section.h @@ -196,10 +196,9 @@ _PyCriticalSection2_Begin(PyThreadState *tstate, PyCriticalSection2 *c, PyObject static inline void _PyCriticalSection2_End(PyThreadState *tstate, PyCriticalSection2 *c) { - // if mutex1 is NULL, we used the fast path in - // _PyCriticalSection_BeginSlow for mutexes that are already held, - // which should only happen when mutex1 and mutex2 were the same mutex, - // and mutex2 should also be NULL. + // if mutex1 is NULL, we used the fast path in either + // _PyCriticalSection_BeginSlow or _PyCriticalSection2_BeginSlow for mutexes + // that are already held, and mutex2 should also be NULL. if (c->_cs_base._cs_mutex == NULL) { assert(c->_cs_mutex2 == NULL); return; diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2026-06-08-13-14-42.gh-issue-150902.-CWZ66.rst b/Misc/NEWS.d/next/Core_and_Builtins/2026-06-08-13-14-42.gh-issue-150902.-CWZ66.rst new file mode 100644 index 00000000000000..e3b7cd387b439f --- /dev/null +++ b/Misc/NEWS.d/next/Core_and_Builtins/2026-06-08-13-14-42.gh-issue-150902.-CWZ66.rst @@ -0,0 +1 @@ +Apply an existing optimization of PyCriticalSection (single mutex) to PyCriticalSection2: avoid acquiring the same locks that the current CS has already acquired. diff --git a/Python/critical_section.c b/Python/critical_section.c index 98e23eda7cdd77..dbee6f236a73be 100644 --- a/Python/critical_section.c +++ b/Python/critical_section.c @@ -72,6 +72,22 @@ _PyCriticalSection2_BeginSlow(PyThreadState *tstate, PyCriticalSection2 *c, PyMu c->_cs_base._cs_prev = 0; return; } + // Same optimization as in _PyCriticalSection_BeginSlow: skip locking when + // recursively acquiring the same locks. + if (tstate->critical_section && + tstate->critical_section & _Py_CRITICAL_SECTION_TWO_MUTEXES) { + PyCriticalSection2 *prev2 = (PyCriticalSection2 *) + untag_critical_section(tstate->critical_section); + assert((uintptr_t)m1 < (uintptr_t)m2); + assert((uintptr_t)prev2->_cs_base._cs_mutex < + (uintptr_t)prev2->_cs_mutex2); + if (prev2->_cs_base._cs_mutex == m1 && prev2->_cs_mutex2 == m2) { + c->_cs_base._cs_mutex = NULL; + c->_cs_mutex2 = NULL; + c->_cs_base._cs_prev = 0; + return; + } + } c->_cs_base._cs_mutex = NULL; c->_cs_mutex2 = NULL; c->_cs_base._cs_prev = tstate->critical_section; _______________________________________________ Python-checkins mailing list -- [email protected] To unsubscribe send an email to [email protected] https://mail.python.org/mailman3//lists/python-checkins.python.org Member address: [email protected]
