From: Miss Islington (bot) <31488909+miss-islington@users.noreply.github.com>
Date: Fri, 22 Nov 2024 14:51:40 +0000 (+0100)
Subject: [3.13] gh-127065: Make `methodcaller` thread-safe in free threading build (GH-127109... 
X-Git-Tag: v3.13.1~67
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=5468d219df65d4fe3335e2bcc09d2f6032a32c70;p=thirdparty%2FPython%2Fcpython.git

[3.13] gh-127065: Make `methodcaller` thread-safe in free threading build (GH-127109) (GH-127150)

The `methodcaller` C vectorcall implementation uses an arguments array
that is shared across calls. The first argument is modified on every
invocation. This isn't thread-safe in the free threading build. I think
it's also not safe in general, but for now just disable it in the free
threading build.
(cherry picked from commit f83ca6962af973fff6a3124f4bd3d45fea4dd5b8)

Co-authored-by: Sam Gross <colesbury@gmail.com>
---

diff --git a/Misc/NEWS.d/next/Library/2024-11-21-16-23-16.gh-issue-127065.cfL1zd.rst b/Misc/NEWS.d/next/Library/2024-11-21-16-23-16.gh-issue-127065.cfL1zd.rst
new file mode 100644
index 000000000000..83457da467ff
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2024-11-21-16-23-16.gh-issue-127065.cfL1zd.rst
@@ -0,0 +1,2 @@
+Fix crash when calling a :func:`operator.methodcaller` instance from
+multiple threads in the free threading build.
diff --git a/Modules/_operator.c b/Modules/_operator.c
index 793a2d0dfc64..261b5cf64a4a 100644
--- a/Modules/_operator.c
+++ b/Modules/_operator.c
@@ -1572,6 +1572,7 @@ typedef struct {
     vectorcallfunc vectorcall;
 } methodcallerobject;
 
+#ifndef Py_GIL_DISABLED
 static int _methodcaller_initialize_vectorcall(methodcallerobject* mc)
 {
     PyObject* args = mc->xargs;
@@ -1634,6 +1635,7 @@ methodcaller_vectorcall(
             (PyTuple_GET_SIZE(mc->xargs)) | PY_VECTORCALL_ARGUMENTS_OFFSET,
             mc->vectorcall_kwnames);
 }
+#endif
 
 
 /* AC 3.5: variable number of arguments, not currently support by AC */
@@ -1673,7 +1675,14 @@ methodcaller_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
     mc->vectorcall_args = 0;
 
 
+#ifdef Py_GIL_DISABLED
+    // gh-127065: The current implementation of methodcaller_vectorcall
+    // is not thread-safe because it modifies the `vectorcall_args` array,
+    // which is shared across calls.
+    mc->vectorcall = NULL;
+#else
     mc->vectorcall = (vectorcallfunc)methodcaller_vectorcall;
+#endif
 
     PyObject_GC_Track(mc);
     return (PyObject *)mc;