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gh-130263: fix list iterators to use atomics for storing index #130266

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gh-130263: fix list iterators to use atomics for storing index #130266

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18 changes: 18 additions & 0 deletions Lib/test/test_free_threading/test_list.py
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Original file line number Diff line number Diff line change
Expand Up @@ -71,6 +71,24 @@ def reader_func():
for reader in readers:
reader.join()

def test_list_iterator_reduce(self):
l = list(range(100))

for it in [iter(l), iter(reversed(l))]:

def reduce():
for i in range(100):
it.__reduce__()

def setstate():
for i in range(100):
it.__setstate__(i)

t1 = Thread(target=reduce)
t2 = Thread(target=setstate)

with threading_helper.start_threads([t1, t2]):
pass

if __name__ == "__main__":
unittest.main()
8 changes: 4 additions & 4 deletions Objects/listobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -3988,12 +3988,12 @@ listiter_setstate(PyObject *self, PyObject *state)
Py_ssize_t index = PyLong_AsSsize_t(state);
if (index == -1 && PyErr_Occurred())
return NULL;
if (it->it_seq != NULL) {
if (FT_ATOMIC_LOAD_SSIZE_RELAXED(it->it_index) >= 0) {
if (index < -1)
index = -1;
else if (index > PyList_GET_SIZE(it->it_seq))
index = PyList_GET_SIZE(it->it_seq); /* iterator exhausted */
it->it_index = index;
FT_ATOMIC_STORE_SSIZE_RELAXED(it->it_index, index);
}
Py_RETURN_NONE;
}
Expand Down Expand Up @@ -4140,12 +4140,12 @@ listreviter_setstate(PyObject *self, PyObject *state)
Py_ssize_t index = PyLong_AsSsize_t(state);
if (index == -1 && PyErr_Occurred())
return NULL;
if (it->it_seq != NULL) {
if (FT_ATOMIC_LOAD_SSIZE_RELAXED(it->it_index) >= 0) {
if (index < -1)
index = -1;
else if (index > PyList_GET_SIZE(it->it_seq) - 1)
index = PyList_GET_SIZE(it->it_seq) - 1;
it->it_index = index;
FT_ATOMIC_STORE_SSIZE_RELAXED(it->it_index, index);
}
Py_RETURN_NONE;
}
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