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gh-150902: Optimize PyCriticalSection2 to skip locking the same locks held by the current CS2

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This mimics an optimization already present for the single-mutex critical section.
This commit is contained in:
Daniele Parmeggiani
2026-06-16 17:56:37 +01:00
committed by GitHub
parent 7edcaedc53
commit c2ca7724af
3 changed files with 20 additions and 4 deletions
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Python/critical_section.c
+16
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@@ -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;