Stowage/cpython
2
0
Fork 0
mirror of https://github.com/python/cpython.git synced 2026-06-28 03:41:13 +00:00
Code Issues Projects Releases Packages Wiki Activity

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

Browse source 
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
No known key found for this signature in database
GPG key ID: B5690EEEBB952194
3 changed files with 20 additions and 4 deletions
Download patch file Download diff file Expand all files Collapse all files

7
Include/internal/pycore_critical_section.h
View file

@ -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;

1
Misc/NEWS.d/next/Core_and_Builtins/2026-06-08-13-14-42.gh-issue-150902.-CWZ66.rst Normal file
View file

@ -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.

16
Python/critical_section.c
View file

@ -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;