gh-132013: use relaxed atomics in hash of frozenset (#132014)

kumaraditya303 · web-flow · commit 76f6b5e64a8b · 2025-04-02T20:01:05.000+05:30
Use relaxed atomics in hash of `frozenset` to fix TSAN warning.
diff --git a/Objects/setobject.c b/Objects/setobject.c
@@ -793,12 +793,12 @@ frozenset_hash(PyObject *self)
     PySetObject *so = _PySet_CAST(self);
     Py_uhash_t hash;
 
-    if (so->hash != -1) {
-        return so->hash;
+    if (FT_ATOMIC_LOAD_SSIZE_RELAXED(so->hash) != -1) {
+        return FT_ATOMIC_LOAD_SSIZE_RELAXED(so->hash);
     }
 
     hash = frozenset_hash_impl(self);
-    so->hash = hash;
+    FT_ATOMIC_STORE_SSIZE_RELAXED(so->hash, hash);
     return hash;
 }
 

Original file line number	Diff line number	Diff line change
`@@ -793,12 +793,12 @@ frozenset_hash(PyObject *self)`
`793`	`793`	`PySetObject *so = _PySet_CAST(self);`
`794`	`794`	`Py_uhash_t hash;`
`795`	`795`
`796`		`- if (so->hash != -1) {`
`797`		`- return so->hash;`
	`796`	`+ if (FT_ATOMIC_LOAD_SSIZE_RELAXED(so->hash) != -1) {`
	`797`	`+ return FT_ATOMIC_LOAD_SSIZE_RELAXED(so->hash);`
`798`	`798`	`}`
`799`	`799`
`800`	`800`	`hash = frozenset_hash_impl(self);`
`801`		`- so->hash = hash;`
	`801`	`+ FT_ATOMIC_STORE_SSIZE_RELAXED(so->hash, hash);`
`802`	`802`	`return hash;`
`803`	`803`	`}`
`804`	`804`