From: sobolevn <mail@sobolevn.me>
Date: Thu, 6 Feb 2025 13:22:41 +0000 (+0300)
Subject: [3.13] gh-129643: Fix `PyList_Insert` in free-threading builds (GH-129680) (#129725)
X-Git-Tag: v3.13.3~313
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=8529d6414f637a168e970e89815d83759d1211dc;p=thirdparty%2FPython%2Fcpython.git

[3.13] gh-129643: Fix `PyList_Insert` in free-threading builds (GH-129680) (#129725)

(cherry picked from commit 63f0406d5ad25a55e49c3903b29407c50a17cfd5)
---

diff --git a/Misc/NEWS.d/next/Core and Builtins/2025-02-05-11-29-52.gh-issue-129643.4mGzvg.rst b/Misc/NEWS.d/next/Core and Builtins/2025-02-05-11-29-52.gh-issue-129643.4mGzvg.rst
new file mode 100644
index 000000000000..420e1fb9781f
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2025-02-05-11-29-52.gh-issue-129643.4mGzvg.rst	
@@ -0,0 +1 @@
+Fix thread safety of :c:func:`PyList_Insert` in free-threading builds.
diff --git a/Objects/listobject.c b/Objects/listobject.c
index d581fc8b0b29..65a8b06d978d 100644
--- a/Objects/listobject.c
+++ b/Objects/listobject.c
@@ -498,8 +498,8 @@ ins1(PyListObject *self, Py_ssize_t where, PyObject *v)
         where = n;
     items = self->ob_item;
     for (i = n; --i >= where; )
-        items[i+1] = items[i];
-    items[where] = Py_NewRef(v);
+        FT_ATOMIC_STORE_PTR_RELAXED(items[i+1], items[i]);
+    FT_ATOMIC_STORE_PTR_RELEASE(items[where], Py_NewRef(v));
     return 0;
 }