From 535b8d6cd511d79b4b37606ef57d1b56521dc244 Mon Sep 17 00:00:00 2001 From: Joseph Tibbertsma Date: Wed, 25 Jun 2025 09:41:36 -0700 Subject: [PATCH] Fix needless spinning in `_PyMutex_LockTimed` with zero timeout (gh-135872) The free threading build could spin unnecessarily on `_Py_yield()` if the initial compare and swap failed. (cherry picked from commit cbfaf41caf135b8598a560854cd59e992a2ccfed) Co-authored-by: Joseph Tibbertsma --- .../2025-06-23-18-08-32.gh-issue-135871.50C528.rst | 2 ++ Python/lock.c | 2 +- 2 files changed, 3 insertions(+), 1 deletion(-) create mode 100644 Misc/NEWS.d/next/Core_and_Builtins/2025-06-23-18-08-32.gh-issue-135871.50C528.rst diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2025-06-23-18-08-32.gh-issue-135871.50C528.rst b/Misc/NEWS.d/next/Core_and_Builtins/2025-06-23-18-08-32.gh-issue-135871.50C528.rst new file mode 100644 index 00000000000000..ce29ddecefe17f --- /dev/null +++ b/Misc/NEWS.d/next/Core_and_Builtins/2025-06-23-18-08-32.gh-issue-135871.50C528.rst @@ -0,0 +1,2 @@ +Non-blocking mutex lock attempts now return immediately when the lock is busy +instead of briefly spinning in the :term:`free threading` build. diff --git a/Python/lock.c b/Python/lock.c index 28a12ad18352d1..3c0804c468e08d 100644 --- a/Python/lock.c +++ b/Python/lock.c @@ -58,7 +58,7 @@ _PyMutex_LockTimed(PyMutex *m, PyTime_t timeout, _PyLockFlags flags) return PY_LOCK_ACQUIRED; } } - else if (timeout == 0) { + if (timeout == 0) { return PY_LOCK_FAILURE; }