[Python-checkins] gh-132213: use relaxed atomics for set hash (#132215)

[kumaraditya303]

https://github.com/python/cpython/commit/ed99e28d5b5613f7c13691fd854195719d7bff1f
commit: ed99e28d5b5613f7c13691fd854195719d7bff1f
branch: main
author: Kumar Aditya <kumaradi...@python.org>
committer: kumaraditya303 <kumaradi...@python.org>
date: 2025-04-07T21:59:24+05:30
summary:

gh-132213: use relaxed atomics for set hash (#132215)

files:
M Objects/setobject.c

diff --git a/Objects/setobject.c b/Objects/setobject.c
index f65d458f7924c3..acbb53aafc0a26 100644
--- a/Objects/setobject.c
+++ b/Objects/setobject.c
@@ -417,7 +417,7 @@ set_empty_to_minsize(PySetObject *so)
     FT_ATOMIC_STORE_SSIZE_RELAXED(so->used, 0);
     so->mask = PySet_MINSIZE - 1;
     so->table = so->smalltable;
-    so->hash = -1;
+    FT_ATOMIC_STORE_SSIZE_RELAXED(so->hash, -1);
 }
 
 static int
@@ -1243,10 +1243,12 @@ set_swap_bodies(PySetObject *a, PySetObject *b)
 
     if (PyType_IsSubtype(Py_TYPE(a), &PyFrozenSet_Type)  &&
         PyType_IsSubtype(Py_TYPE(b), &PyFrozenSet_Type)) {
-        h = a->hash;     a->hash = b->hash;  b->hash = h;
+        h = FT_ATOMIC_LOAD_SSIZE_RELAXED(a->hash);
+        FT_ATOMIC_STORE_SSIZE_RELAXED(a->hash, 
FT_ATOMIC_LOAD_SSIZE_RELAXED(b->hash));
+        FT_ATOMIC_STORE_SSIZE_RELAXED(b->hash, h);
     } else {
-        a->hash = -1;
-        b->hash = -1;
+        FT_ATOMIC_STORE_SSIZE_RELAXED(a->hash, -1);
+        FT_ATOMIC_STORE_SSIZE_RELAXED(b->hash, -1);
     }
 }
 
@@ -2141,9 +2143,9 @@ set_richcompare(PyObject *self, PyObject *w, int op)
     case Py_EQ:
         if (PySet_GET_SIZE(v) != PySet_GET_SIZE(w))
             Py_RETURN_FALSE;
-        if (v->hash != -1  &&
-            ((PySetObject *)w)->hash != -1 &&
-            v->hash != ((PySetObject *)w)->hash)
+        Py_hash_t v_hash = FT_ATOMIC_LOAD_SSIZE_RELAXED(v->hash);
+        Py_hash_t w_hash = FT_ATOMIC_LOAD_SSIZE_RELAXED(((PySetObject 
*)w)->hash);
+        if (v_hash != -1 && w_hash != -1 && v_hash != w_hash)
             Py_RETURN_FALSE;
         return set_issubset((PyObject*)v, w);
     case Py_NE:

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