gh-128759: fix data race in type_modified_unlocked (GH-128764)

sobolevn · miss-islington · commit acf7da9f5a4b · 2025-01-13T07:41:04.000Z
(cherry picked from commit 6e1e780) Co-authored-by: sobolevn <mail@sobolevn.me>
diff --git a/Objects/typeobject.c b/Objects/typeobject.c
@@ -996,7 +996,7 @@ type_modified_unlocked(PyTypeObject *type)
        We don't assign new version tags eagerly, but only as
        needed.
      */
-    if (type->tp_version_tag == 0) {
+    if (FT_ATOMIC_LOAD_UINT_RELAXED(type->tp_version_tag) == 0) {
         return;
     }
     // Cannot modify static builtin types.

Original file line number	Diff line number	Diff line change
`@@ -996,7 +996,7 @@ type_modified_unlocked(PyTypeObject *type)`
`996`	`996`	`We don't assign new version tags eagerly, but only as`
`997`	`997`	`needed.`
`998`	`998`	`*/`
`999`		`- if (type->tp_version_tag == 0) {`
	`999`	`+ if (FT_ATOMIC_LOAD_UINT_RELAXED(type->tp_version_tag) == 0) {`
`1000`	`1000`	`return;`
`1001`	`1001`	`}`
`1002`	`1002`	`// Cannot modify static builtin types.`