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gh-144356: Make set iterator __length_hint__ and iternext race-safe under no-gil #144357

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gh-144356: Make set iterator __length_hint__ and iternext race-safe under no-gil #144357

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47d75fe
Fix data race in setiter_len() under no-gil
hyongtao-code Jan 31, 2026
3e3785c
Add test case
hyongtao-code Jan 31, 2026
229ced3
📜🤖 Added by blurb_it.
blurb-it[bot] Jan 31, 2026
cdcf88a
Resovle comments
hyongtao-code Feb 1, 2026
21f1478
Update test case: used_race and exhaust_race
hyongtao-code Feb 1, 2026
a18c698
Add test case
hyongtao-code Feb 6, 2026
79b5fbc
Try to address the comments
hyongtao-code Feb 6, 2026
6ac15e0
Post fix
hyongtao-code Feb 6, 2026
3222eef
Address comments
hyongtao-code Feb 8, 2026
7fb39bc
Post fix
hyongtao-code Feb 8, 2026
78241a8
Update Lib/test/test_free_threading/test_set.py
hyongtao-code Feb 9, 2026
52285a2
Revert "Update Lib/test/test_free_threading/test_set.py"
hyongtao-code Feb 9, 2026
c9ece31
Address comments
hyongtao-code Feb 9, 2026
e41e852
Enhance the test case as test_itertools.py
hyongtao-code Feb 10, 2026
b32b5ec
Update NEWS
hyongtao-code Feb 10, 2026
d14856c
Address comment
hyongtao-code Feb 10, 2026
2a512a8
Address comments
hyongtao-code Feb 10, 2026
1ce898a
Update test cases
hyongtao-code Feb 11, 2026
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Address comments: unused code
hyongtao-code Feb 13, 2026
6120aef
Update Lib/test/test_free_threading/test_set.py
hyongtao-code Feb 13, 2026
afea804
Update Objects/setobject.c
hyongtao-code Feb 13, 2026
dc4eaa6
Remove empyt line
hyongtao-code Feb 14, 2026
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Address comments
hyongtao-code Mar 11, 2026
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Merge branch 'main' into fix-data-race
hyongtao-code May 19, 2026
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Update test case: used_race and exhaust_race
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hyongtao-code committed Feb 1, 2026
commit 21f1478423e09eee0ea7c082d46fe5d6291e2cc3
22 changes: 20 additions & 2 deletions Objects/setobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1056,9 +1056,23 @@ setiter_len(PyObject *op, PyObject *Py_UNUSED(ignored))
{
setiterobject *si = (setiterobject*)op;
Py_ssize_t len = 0;
PySetObject *so = si->si_set;
if (so != NULL && si->si_used == FT_ATOMIC_LOAD_SSIZE_RELAXED(so->used))
#ifdef Py_GIL_DISABLED
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PyObject *so_obj = FT_ATOMIC_LOAD_PTR_ACQUIRE(si->si_set);
if (so_obj != NULL) {
/* Turn borrowed si->si_set into a strong ref safely. */
if (_Py_TryIncrefCompare((PyObject **)&si->si_set, so_obj)) {
PySetObject *so = (PySetObject *)so_obj;
if (si->si_used == FT_ATOMIC_LOAD_SSIZE_RELAXED(so->used)) {
len = si->len;
}
Py_DECREF(so_obj);
}
}
#else
if (si->si_set != NULL && si->si_used == si->si_set->used) {
len = si->len;
}
#endif
return PyLong_FromSsize_t(len);
}

Expand Down Expand Up @@ -1125,7 +1139,11 @@ static PyObject *setiter_iternext(PyObject *self)
Py_END_CRITICAL_SECTION();
si->si_pos = i+1;
if (key == NULL) {
#ifdef Py_GIL_DISABLED
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FT_ATOMIC_STORE_PTR_RELEASE(si->si_set, NULL);
#else
si->si_set = NULL;
#endif
Py_DECREF(so);

@eendebakpt eendebakpt Feb 10, 2026

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Can you move the decref to the section

       /* exhausted */
        si->si_pos = -1;
        si->len = 0;

?

@hyongtao-code hyongtao-code Feb 13, 2026

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I’d prefer not to move the Py_DECREF into the Py_BEGIN_CRITICAL_SECTION block.

return NULL;
}
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