https://github.com/python/cpython/commit/57f45ee2d8ee23c2a1d1daba4095a5a044169419
commit: 57f45ee2d8ee23c2a1d1daba4095a5a044169419
branch: main
author: Sam Gross <[email protected]>
committer: colesbury <[email protected]>
date: 2025-02-12T09:34:40-05:00
summary:
gh-128759: Fix accesses to `tp_version_tag`. (GH-129750)
We should use a relaxed atomic load in the free threading build in
`PyType_Modified()` because that's called without the type lock held.
It's not necessary to use atomics in `type_modified_unlocked()`.
We should also use `FT_ATOMIC_STORE_UINT_RELAXED()` instead of the
`UINT32` variant because `tp_version_tag` is declared as `unsigned int`.
files:
M Objects/typeobject.c
diff --git a/Objects/typeobject.c b/Objects/typeobject.c
index 59ea2e3331ff54..1484d9b33417b2 100644
--- a/Objects/typeobject.c
+++ b/Objects/typeobject.c
@@ -1010,7 +1010,7 @@ set_version_unlocked(PyTypeObject *tp, unsigned int
version)
_Py_atomic_add_uint16(&tp->tp_versions_used, 1);
}
#endif
- FT_ATOMIC_STORE_UINT32_RELAXED(tp->tp_version_tag, version);
+ FT_ATOMIC_STORE_UINT_RELAXED(tp->tp_version_tag, version);
#ifndef Py_GIL_DISABLED
if (version != 0) {
PyTypeObject **slot =
@@ -1039,7 +1039,8 @@ type_modified_unlocked(PyTypeObject *type)
We don't assign new version tags eagerly, but only as
needed.
*/
- if (FT_ATOMIC_LOAD_UINT_RELAXED(type->tp_version_tag) == 0) {
+ ASSERT_TYPE_LOCK_HELD();
+ if (type->tp_version_tag == 0) {
return;
}
// Cannot modify static builtin types.
@@ -1094,7 +1095,7 @@ void
PyType_Modified(PyTypeObject *type)
{
// Quick check without the lock held
- if (type->tp_version_tag == 0) {
+ if (FT_ATOMIC_LOAD_UINT_RELAXED(type->tp_version_tag) == 0) {
return;
}
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