https://github.com/python/cpython/commit/e8e044eda343b4b3dd7a7e532c88c2c97242000d
commit: e8e044eda343b4b3dd7a7e532c88c2c97242000d
branch: main
author: Sam Gross <[email protected]>
committer: colesbury <[email protected]>
date: 2025-12-24T08:02:19-05:00
summary:
gh-143100: Fix memcpy data race in setobject.c (gh-143127)
files:
M Objects/setobject.c
M Tools/tsan/suppressions_free_threading.txt
diff --git a/Objects/setobject.c b/Objects/setobject.c
index 5f868c858273ee..55e30fe2cdd8f7 100644
--- a/Objects/setobject.c
+++ b/Objects/setobject.c
@@ -1420,6 +1420,17 @@ set_new(PyTypeObject *type, PyObject *args, PyObject
*kwds)
return make_new_set(type, NULL);
}
+#ifdef Py_GIL_DISABLED
+static void
+copy_small_table(setentry *dest, setentry *src)
+{
+ for (Py_ssize_t i = 0; i < PySet_MINSIZE; i++) {
+ _Py_atomic_store_ptr_release(&dest[i].key, src[i].key);
+ _Py_atomic_store_ssize_relaxed(&dest[i].hash, src[i].hash);
+ }
+}
+#endif
+
/* set_swap_bodies() switches the contents of any two sets by moving their
internal data pointers and, if needed, copying the internal smalltables.
Semantically equivalent to:
@@ -1462,8 +1473,13 @@ set_swap_bodies(PySetObject *a, PySetObject *b)
if (a_table == a->smalltable || b_table == b->smalltable) {
memcpy(tab, a->smalltable, sizeof(tab));
+#ifndef Py_GIL_DISABLED
memcpy(a->smalltable, b->smalltable, sizeof(tab));
memcpy(b->smalltable, tab, sizeof(tab));
+#else
+ copy_small_table(a->smalltable, b->smalltable);
+ copy_small_table(b->smalltable, tab);
+#endif
}
if (PyType_IsSubtype(Py_TYPE(a), &PyFrozenSet_Type) &&
diff --git a/Tools/tsan/suppressions_free_threading.txt
b/Tools/tsan/suppressions_free_threading.txt
index f05e0ded9865f8..a3e1e54284f0ae 100644
--- a/Tools/tsan/suppressions_free_threading.txt
+++ b/Tools/tsan/suppressions_free_threading.txt
@@ -20,6 +20,3 @@ thread:pthread_create
# PyObject_Realloc internally does memcpy which isn't atomic so can race
# with non-locking reads. See #132070
race:PyObject_Realloc
-
-# gh-143100: set_swap_bodies in setobject.c calls memcpy, which isn't atomic
-race:set_swap_bodies
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