From 0d03a185ac784ffb057885022aa3000b294e66f3 Mon Sep 17 00:00:00 2001 From: Daniele Parmeggiani Date: Mon, 8 Jun 2026 14:11:17 +0100 Subject: [PATCH 1/3] gh-150902: Optimize `PyCriticalSection2` to skip locking the same locks as the ones held by the current CS2 --- Python/critical_section.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+) diff --git a/Python/critical_section.c b/Python/critical_section.c index 98e23eda7cdd77e..a2673f51fe73180 100644 --- a/Python/critical_section.c +++ b/Python/critical_section.c @@ -72,6 +72,21 @@ _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(m1 < m2); + assert(prev2->_cs_base._cs_mutex < 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; From b61696ed0d137d2cd4ac40bf59a0bf48af9a2764 Mon Sep 17 00:00:00 2001 From: "blurb-it[bot]" <43283697+blurb-it[bot]@users.noreply.github.com> Date: Mon, 8 Jun 2026 13:14:46 +0000 Subject: [PATCH 2/3] =?UTF-8?q?=F0=9F=93=9C=F0=9F=A4=96=20Added=20by=20blu?= =?UTF-8?q?rb=5Fit.?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- .../2026-06-08-13-14-42.gh-issue-150902.-CWZ66.rst | 1 + 1 file changed, 1 insertion(+) create mode 100644 Misc/NEWS.d/next/Core_and_Builtins/2026-06-08-13-14-42.gh-issue-150902.-CWZ66.rst 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 000000000000000..e3b7cd387b439fe --- /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. From 5dd3cf364a51702143bcdf8c60ea923b4c97f3f4 Mon Sep 17 00:00:00 2001 From: Daniele Parmeggiani Date: Tue, 16 Jun 2026 17:24:58 +0100 Subject: [PATCH 3/3] review comments --- Include/internal/pycore_critical_section.h | 7 +++---- Python/critical_section.c | 5 +++-- 2 files changed, 6 insertions(+), 6 deletions(-) diff --git a/Include/internal/pycore_critical_section.h b/Include/internal/pycore_critical_section.h index 2a2846b1296b901..51d99d74ca159f6 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/Python/critical_section.c b/Python/critical_section.c index a2673f51fe73180..dbee6f236a73bea 100644 --- a/Python/critical_section.c +++ b/Python/critical_section.c @@ -78,8 +78,9 @@ _PyCriticalSection2_BeginSlow(PyThreadState *tstate, PyCriticalSection2 *c, PyMu tstate->critical_section & _Py_CRITICAL_SECTION_TWO_MUTEXES) { PyCriticalSection2 *prev2 = (PyCriticalSection2 *) untag_critical_section(tstate->critical_section); - assert(m1 < m2); - assert(prev2->_cs_base._cs_mutex < prev2->_cs_mutex2); + 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;