https://github.com/python/cpython/commit/13835888e697e7412b905a55d78755ed7a1... commit: 13835888e697e7412b905a55d78755ed7a132c5c branch: 3.13 author: Thomas Grainger <tagrain@gmail.com> committer: kumaraditya303 <kumaraditya@python.org> date: 2025-01-08T18:16:43+05:30 summary: [3.13] gh-128552: fix refcycles in eager task creation (#128553) (#128585) gh-128552: fix refcycles in eager task creation (#128553) (cherry picked from commit 61b9811ac6843e22b5896ef96030d421b79cd892) files: A Misc/NEWS.d/next/Library/2025-01-06-18-41-08.gh-issue-128552.fV-f8j.rst M Lib/asyncio/base_events.py M Lib/asyncio/taskgroups.py M Lib/test/test_asyncio/test_taskgroups.py diff --git a/Lib/asyncio/base_events.py b/Lib/asyncio/base_events.py index 91434042685239..ca29792dc89825 100644 --- a/Lib/asyncio/base_events.py +++ b/Lib/asyncio/base_events.py @@ -477,7 +477,12 @@ def create_task(self, coro, *, name=None, context=None): task.set_name(name) - return task + try: + return task + finally: + # gh-128552: prevent a refcycle of + # task.exception().__traceback__->BaseEventLoop.create_task->task + del task def set_task_factory(self, factory): """Set a task factory that will be used by loop.create_task(). diff --git a/Lib/asyncio/taskgroups.py b/Lib/asyncio/taskgroups.py index 9fa772ca9d02cc..8af199d6dcc41a 100644 --- a/Lib/asyncio/taskgroups.py +++ b/Lib/asyncio/taskgroups.py @@ -205,7 +205,12 @@ def create_task(self, coro, *, name=None, context=None): else: self._tasks.add(task) task.add_done_callback(self._on_task_done) - return task + try: + return task + finally: + # gh-128552: prevent a refcycle of + # task.exception().__traceback__->TaskGroup.create_task->task + del task # Since Python 3.8 Tasks propagate all exceptions correctly, # except for KeyboardInterrupt and SystemExit which are diff --git a/Lib/test/test_asyncio/test_taskgroups.py b/Lib/test/test_asyncio/test_taskgroups.py index 138f59ebf57ef7..e52061aac923cc 100644 --- a/Lib/test/test_asyncio/test_taskgroups.py +++ b/Lib/test/test_asyncio/test_taskgroups.py @@ -1,6 +1,8 @@ # Adapted with permission from the EdgeDB project; # license: PSFL. +import weakref +import sys import gc import asyncio import contextvars @@ -28,7 +30,25 @@ def get_error_types(eg): return {type(exc) for exc in eg.exceptions} -class TestTaskGroup(unittest.IsolatedAsyncioTestCase): +def set_gc_state(enabled): + was_enabled = gc.isenabled() + if enabled: + gc.enable() + else: + gc.disable() + return was_enabled + + +@contextlib.contextmanager +def disable_gc(): + was_enabled = set_gc_state(enabled=False) + try: + yield + finally: + set_gc_state(enabled=was_enabled) + + +class BaseTestTaskGroup: async def test_taskgroup_01(self): @@ -822,15 +842,15 @@ async def test_taskgroup_without_parent_task(self): with self.assertRaisesRegex(RuntimeError, "has not been entered"): tg.create_task(coro) - def test_coro_closed_when_tg_closed(self): + async def test_coro_closed_when_tg_closed(self): async def run_coro_after_tg_closes(): async with taskgroups.TaskGroup() as tg: pass coro = asyncio.sleep(0) with self.assertRaisesRegex(RuntimeError, "is finished"): tg.create_task(coro) - loop = asyncio.get_event_loop() - loop.run_until_complete(run_coro_after_tg_closes()) + + await run_coro_after_tg_closes() async def test_cancelling_level_preserved(self): async def raise_after(t, e): @@ -955,6 +975,30 @@ async def coro_fn(): self.assertIsInstance(exc, _Done) self.assertListEqual(gc.get_referrers(exc), []) + + async def test_exception_refcycles_parent_task_wr(self): + """Test that TaskGroup deletes self._parent_task and create_task() deletes task""" + tg = asyncio.TaskGroup() + exc = None + + class _Done(Exception): + pass + + async def coro_fn(): + async with tg: + raise _Done + + with disable_gc(): + try: + async with asyncio.TaskGroup() as tg2: + task_wr = weakref.ref(tg2.create_task(coro_fn())) + except* _Done as excs: + exc = excs.exceptions[0].exceptions[0] + + self.assertIsNone(task_wr()) + self.assertIsInstance(exc, _Done) + self.assertListEqual(gc.get_referrers(exc), []) + async def test_exception_refcycles_propagate_cancellation_error(self): """Test that TaskGroup deletes propagate_cancellation_error""" tg = asyncio.TaskGroup() @@ -988,5 +1032,16 @@ class MyKeyboardInterrupt(KeyboardInterrupt): self.assertListEqual(gc.get_referrers(exc), []) +class TestTaskGroup(BaseTestTaskGroup, unittest.IsolatedAsyncioTestCase): + loop_factory = asyncio.EventLoop + +class TestEagerTaskTaskGroup(BaseTestTaskGroup, unittest.IsolatedAsyncioTestCase): + @staticmethod + def loop_factory(): + loop = asyncio.EventLoop() + loop.set_task_factory(asyncio.eager_task_factory) + return loop + + if __name__ == "__main__": unittest.main() diff --git a/Misc/NEWS.d/next/Library/2025-01-06-18-41-08.gh-issue-128552.fV-f8j.rst b/Misc/NEWS.d/next/Library/2025-01-06-18-41-08.gh-issue-128552.fV-f8j.rst new file mode 100644 index 00000000000000..83816f775da9c5 --- /dev/null +++ b/Misc/NEWS.d/next/Library/2025-01-06-18-41-08.gh-issue-128552.fV-f8j.rst @@ -0,0 +1 @@ +Fix cyclic garbage introduced by :meth:`asyncio.loop.create_task` and :meth:`asyncio.TaskGroup.create_task` holding a reference to the created task if it is eager.