https://github.com/python/cpython/commit/009c8c052f5eb9f869c09029724ef194d8c161ca
commit: 009c8c052f5eb9f869c09029724ef194d8c161ca
branch: main
author: Pieter Eendebak <[email protected]>
committer: colesbury <[email protected]>
date: 2026-02-04T13:38:45-05:00
summary:
gh-123471: Make concurrent iteration over `itertools.permutations` and
`itertools.combinations_with_replacement` thread-safe (gh-144402)
files:
A Misc/NEWS.d/next/Library/2026-02-03-08-50-58.gh-issue-123471.yF1Gym.rst
M Lib/test/test_free_threading/test_itertools.py
M Modules/itertoolsmodule.c
diff --git a/Lib/test/test_free_threading/test_itertools.py
b/Lib/test/test_free_threading/test_itertools.py
index 9d366041917bb3..bb6047e8669475 100644
--- a/Lib/test/test_free_threading/test_itertools.py
+++ b/Lib/test/test_free_threading/test_itertools.py
@@ -1,94 +1,59 @@
import unittest
-from threading import Thread, Barrier
-from itertools import batched, chain, cycle
+from itertools import batched, chain, combinations_with_replacement, cycle,
permutations
from test.support import threading_helper
threading_helper.requires_working_threading(module=True)
-class ItertoolsThreading(unittest.TestCase):
-
- @threading_helper.reap_threads
- def test_batched(self):
- number_of_threads = 10
- number_of_iterations = 20
- barrier = Barrier(number_of_threads)
- def work(it):
- barrier.wait()
- while True:
- try:
- next(it)
- except StopIteration:
- break
- data = tuple(range(1000))
- for it in range(number_of_iterations):
- batch_iterator = batched(data, 2)
- worker_threads = []
- for ii in range(number_of_threads):
- worker_threads.append(
- Thread(target=work, args=[batch_iterator]))
+def work_iterator(it):
+ while True:
+ try:
+ next(it)
+ except StopIteration:
+ break
- with threading_helper.start_threads(worker_threads):
- pass
- barrier.reset()
+class ItertoolsThreading(unittest.TestCase):
@threading_helper.reap_threads
- def test_cycle(self):
- number_of_threads = 6
+ def test_batched(self):
number_of_iterations = 10
- number_of_cycles = 400
+ for _ in range(number_of_iterations):
+ it = batched(tuple(range(1000)), 2)
+ threading_helper.run_concurrently(work_iterator, nthreads=10,
args=[it])
- barrier = Barrier(number_of_threads)
+ @threading_helper.reap_threads
+ def test_cycle(self):
def work(it):
- barrier.wait()
- for _ in range(number_of_cycles):
- try:
- next(it)
- except StopIteration:
- pass
+ for _ in range(400):
+ next(it)
- data = (1, 2, 3, 4)
- for it in range(number_of_iterations):
- cycle_iterator = cycle(data)
- worker_threads = []
- for ii in range(number_of_threads):
- worker_threads.append(
- Thread(target=work, args=[cycle_iterator]))
-
- with threading_helper.start_threads(worker_threads):
- pass
-
- barrier.reset()
+ number_of_iterations = 6
+ for _ in range(number_of_iterations):
+ it = cycle((1, 2, 3, 4))
+ threading_helper.run_concurrently(work, nthreads=6, args=[it])
@threading_helper.reap_threads
def test_chain(self):
- number_of_threads = 6
- number_of_iterations = 20
-
- barrier = Barrier(number_of_threads)
- def work(it):
- barrier.wait()
- while True:
- try:
- next(it)
- except StopIteration:
- break
-
- data = [(1, )] * 200
- for it in range(number_of_iterations):
- chain_iterator = chain(*data)
- worker_threads = []
- for ii in range(number_of_threads):
- worker_threads.append(
- Thread(target=work, args=[chain_iterator]))
-
- with threading_helper.start_threads(worker_threads):
- pass
+ number_of_iterations = 10
+ for _ in range(number_of_iterations):
+ it = chain(*[(1,)] * 200)
+ threading_helper.run_concurrently(work_iterator, nthreads=6,
args=[it])
- barrier.reset()
+ @threading_helper.reap_threads
+ def test_combinations_with_replacement(self):
+ number_of_iterations = 6
+ for _ in range(number_of_iterations):
+ it = combinations_with_replacement(tuple(range(2)), 2)
+ threading_helper.run_concurrently(work_iterator, nthreads=6,
args=[it])
+ @threading_helper.reap_threads
+ def test_permutations(self):
+ number_of_iterations = 6
+ for _ in range(number_of_iterations):
+ it = permutations(tuple(range(4)), 2)
+ threading_helper.run_concurrently(work_iterator, nthreads=6,
args=[it])
if __name__ == "__main__":
diff --git
a/Misc/NEWS.d/next/Library/2026-02-03-08-50-58.gh-issue-123471.yF1Gym.rst
b/Misc/NEWS.d/next/Library/2026-02-03-08-50-58.gh-issue-123471.yF1Gym.rst
new file mode 100644
index 00000000000000..85e9a03426e1fc
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2026-02-03-08-50-58.gh-issue-123471.yF1Gym.rst
@@ -0,0 +1 @@
+Make concurrent iteration over
:class:`itertools.combinations_with_replacement` and
:class:`itertools.permutations` safe under free-threading.
diff --git a/Modules/itertoolsmodule.c b/Modules/itertoolsmodule.c
index 8685eff8be65c3..7e73f76bc20b58 100644
--- a/Modules/itertoolsmodule.c
+++ b/Modules/itertoolsmodule.c
@@ -2587,7 +2587,7 @@ cwr_traverse(PyObject *op, visitproc visit, void *arg)
}
static PyObject *
-cwr_next(PyObject *op)
+cwr_next_lock_held(PyObject *op)
{
cwrobject *co = cwrobject_CAST(op);
PyObject *elem;
@@ -2666,6 +2666,16 @@ cwr_next(PyObject *op)
return NULL;
}
+static PyObject *
+cwr_next(PyObject *op)
+{
+ PyObject *result;
+ Py_BEGIN_CRITICAL_SECTION(op);
+ result = cwr_next_lock_held(op);
+ Py_END_CRITICAL_SECTION()
+ return result;
+}
+
static PyMethodDef cwr_methods[] = {
{"__sizeof__", cwr_sizeof, METH_NOARGS, sizeof_doc},
{NULL, NULL} /* sentinel */
@@ -2846,7 +2856,7 @@ permutations_traverse(PyObject *op, visitproc visit, void
*arg)
}
static PyObject *
-permutations_next(PyObject *op)
+permutations_next_lock_held(PyObject *op)
{
permutationsobject *po = permutationsobject_CAST(op);
PyObject *elem;
@@ -2936,6 +2946,16 @@ permutations_next(PyObject *op)
return NULL;
}
+static PyObject *
+permutations_next(PyObject *op)
+{
+ PyObject *result;
+ Py_BEGIN_CRITICAL_SECTION(op);
+ result = permutations_next_lock_held(op);
+ Py_END_CRITICAL_SECTION()
+ return result;
+}
+
static PyMethodDef permuations_methods[] = {
{"__sizeof__", permutations_sizeof, METH_NOARGS, sizeof_doc},
{NULL, NULL} /* sentinel */
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