https://github.com/python/cpython/commit/59cba59b153b2980930999d20ccf97e44fb6edf5
commit: 59cba59b153b2980930999d20ccf97e44fb6edf5
branch: main
author: Duprat <[email protected]>
committer: kumaraditya303 <[email protected]>
date: 2026-09-11T18:06:33+05:30
summary:
gh-108549: fix asyncio.Task cancellation swallowing SystemExit and
KeyboardInterrupt (#156309)
files:
A Misc/NEWS.d/next/Library/2026-08-24-14-28-47.gh-issue-108549.XZ34WD.rst
M Lib/asyncio/tasks.py
M Lib/test/test_asyncio/test_tasks.py
M Modules/_asynciomodule.c
diff --git a/Lib/asyncio/tasks.py b/Lib/asyncio/tasks.py
index f432cf0afa895a2..8f4dce831c5ccce 100644
--- a/Lib/asyncio/tasks.py
+++ b/Lib/asyncio/tasks.py
@@ -268,7 +268,9 @@ def __step(self, exc=None):
raise exceptions.InvalidStateError(
f'__step(): already done: {self!r}, {exc!r}')
if self._must_cancel:
- if not isinstance(exc, exceptions.CancelledError):
+ # gh-108549: do not swallow SystemExit and KeyboardInterrupt.
+ if not isinstance(exc, (exceptions.CancelledError,
+ SystemExit, KeyboardInterrupt)):
exc = self._make_cancelled_error()
self._must_cancel = False
self._fut_waiter = None
diff --git a/Lib/test/test_asyncio/test_tasks.py
b/Lib/test/test_asyncio/test_tasks.py
index 9c111da8c27f162..fa3eaef0ac03375 100644
--- a/Lib/test/test_asyncio/test_tasks.py
+++ b/Lib/test/test_asyncio/test_tasks.py
@@ -1891,6 +1891,30 @@ async def notmuch():
self.loop.run_until_complete(task),
'ko')
+ def test_step_dont_swallow_systemexit_or_keyboardinterrupt(self):
+ # see gh-108549: do not swallow SystemExit and KeyboardInterrupt
+ # in Task.__step when the current task must be cancelled.
+ async def sub_task(exc):
+ raise exc
+
+ async def current_task(exc):
+ try:
+ await asyncio.create_task(sub_task(exc))
+ except exc:
+ pass
+ except BaseException as e:
+ self.fail(f'{exc} is expected, instead of {type(e)}')
+ return "ok"
+
+ for exc in (SystemExit, KeyboardInterrupt):
+ with self.subTest(exc):
+ t = self.new_task(self.loop, current_task(exc))
+ self.assertRaises(exc, self.loop.run_until_complete, t)
+ t.cancel()
+ test_utils.run_briefly(self.loop)
+ self.assertTrue(not t.cancelled())
+ self.assertEqual(t.result(), "ok")
+
def test_step_result_future(self):
# If coroutine returns future, task waits on this future.
diff --git
a/Misc/NEWS.d/next/Library/2026-08-24-14-28-47.gh-issue-108549.XZ34WD.rst
b/Misc/NEWS.d/next/Library/2026-08-24-14-28-47.gh-issue-108549.XZ34WD.rst
new file mode 100644
index 000000000000000..c6b7605f1b0eb56
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2026-08-24-14-28-47.gh-issue-108549.XZ34WD.rst
@@ -0,0 +1,3 @@
+Fix :class:`asyncio.Task`, when the task has a pending cancellation,
+replace **exc** exception with a :exc:`asyncio.CancelledError` unless it is
+:exc:`SystemExit` or :exc:`KeyboardInterrupt`, which must propagate unchanged.
diff --git a/Modules/_asynciomodule.c b/Modules/_asynciomodule.c
index a380f8ac72b32f4..8c90b0b1517ae4e 100644
--- a/Modules/_asynciomodule.c
+++ b/Modules/_asynciomodule.c
@@ -3051,8 +3051,13 @@ task_step_impl(asyncio_state *state, TaskObj *task,
PyObject *exc)
if (task->task_must_cancel) {
assert(exc != Py_None);
- if (!exc || !PyErr_GivenExceptionMatches(exc,
state->asyncio_CancelledError)) {
- /* exc was not a CancelledError */
+ /* Replace exc with a CancelledError unless it already is one, or
+ it is SystemExit/KeyboardInterrupt, which must propagate
+ unchanged (gh-108549). */
+ if (!exc ||
+ (!PyErr_GivenExceptionMatches(exc, state->asyncio_CancelledError)
&&
+ !PyErr_GivenExceptionMatches(exc, PyExc_KeyboardInterrupt) &&
+ !PyErr_GivenExceptionMatches(exc, PyExc_SystemExit))) {
exc = create_cancelled_error(state, (FutureObj*)task);
if (!exc) {
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