From: Sam Gross <colesbury@gmail.com>
Date: Fri, 16 Jan 2026 16:55:40 +0000 (-0500)
Subject: [3.14] gh-143880: Fix data race in `functools.partial` in free threading build (... 
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=0042384bd56cf88c9bf868776247ef00b34719de;p=thirdparty%2FPython%2Fcpython.git

[3.14] gh-143880: Fix data race in `functools.partial` in free threading build (#143882)

gh-143880: Fix data race in `functools.partial` in free threading build

The assignment to `pto->vectorcall` isn't thread-safe in the free
threading build. Note that this is already fixed in the main branch.
---

diff --git a/Misc/NEWS.d/next/Library/2026-01-15-13-03-22.gh-issue-143880.sWoLsf.rst b/Misc/NEWS.d/next/Library/2026-01-15-13-03-22.gh-issue-143880.sWoLsf.rst
new file mode 100644
index 000000000000..b77f86e5eb8f
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2026-01-15-13-03-22.gh-issue-143880.sWoLsf.rst
@@ -0,0 +1 @@
+Fix data race in :func:`functools.partial` in the :term:`free threading` build.
diff --git a/Modules/_functoolsmodule.c b/Modules/_functoolsmodule.c
index 3420e7d8c37b..490c6b83d217 100644
--- a/Modules/_functoolsmodule.c
+++ b/Modules/_functoolsmodule.c
@@ -375,7 +375,9 @@ partial_vectorcall_fallback(PyThreadState *tstate, partialobject *pto,
                             PyObject *const *args, size_t nargsf,
                             PyObject *kwnames)
 {
+#ifndef Py_GIL_DISABLED
     pto->vectorcall = NULL;
+#endif
     Py_ssize_t nargs = PyVectorcall_NARGS(nargsf);
     return _PyObject_MakeTpCall(tstate, (PyObject *)pto, args, nargs, kwnames);
 }