`memcpy` data race in `setobject.c`

[colesbury]

Bug report

Seen when running locally. We should use the ptr_wise_atomic_memmove from listobject.c.

WARNING: ThreadSanitizer: data race (pid=833878)
  Write of size 8 at 0x7fffb57ba460 by thread T10318:
    #0 __tsan_memcpy <null> (python+0xf4b62) (BuildId: 62048a720cd5edc7e743b66781182a91a8a5cb4a)
    #1 set_swap_bodies /home/sgross/cpython/Objects/setobject.c:1465:9 (python+0x396739) (BuildId: 62048a720cd5edc7e743b66781182a91a8a5cb4a)
    #2 set_intersection_update /home/sgross/cpython/Objects/setobject.c:1740:5 (python+0x391a91) (BuildId: 62048a720cd5edc7e743b66781182a91a8a5cb4a)
    #3 set_iand /home/sgross/cpython/Objects/setobject.c:1795:14 (python+0x391a91)
...

  Previous atomic read of size 8 at 0x7fffb57ba460 by thread T10317:
    #0 _Py_atomic_load_ptr_acquire /home/sgross/cpython/./Include/cpython/pyatomic_gcc.h:557:18 (python+0x38bb7c) (BuildId: 62048a720cd5edc7e743b66781182a91a8a5cb4a)
    #1 set_compare_threadsafe /home/sgross/cpython/Objects/setobject.c:100:26 (python+0x38bb7c)
    #2 set_do_lookup /home/sgross/cpython/Objects/setobject.c:234:22 (python+0x38bb7c)
    #3 set_lookkey_threadsafe /home/sgross/cpython/Objects/setobject.c:452:14 (python+0x38bb7c)
    #4 set_contains_entry /home/sgross/cpython/Objects/setobject.c:566:12 (python+0x38bb7c)

cpython/Objects/setobject.c

Lines 1463 to 1467 in 6536fab

	if (a_table == a->smalltable || b_table == b->smalltable) {
	memcpy(tab, a->smalltable, sizeof(tab));
	memcpy(a->smalltable, b->smalltable, sizeof(tab));
	memcpy(b->smalltable, tab, sizeof(tab));
	}

cpython/Objects/setobject.c

Lines 96 to 100 in 6536fab

	static inline Py_ALWAYS_INLINE int
	set_compare_threadsafe(PySetObject *so, setentry *table, setentry *ep,
	PyObject *key, Py_hash_t hash)
	{
	PyObject *startkey = FT_ATOMIC_LOAD_PTR_ACQUIRE(ep->key);

Linked PRs

• gh-143100: Add temporary suppression for set_swap_bodies #143114
• gh-143100: Fix memcpy data race in setobject.c #143127