From a2118a14627256197bddcf4fcecad4c264c1e39d Mon Sep 17 00:00:00 2001 From: Elvis Pranskevichus Date: Wed, 26 Aug 2020 09:42:45 -0700 Subject: bpo-37658: Fix asyncio.wait_for() to respect waited task status (#21894) Currently, if `asyncio.wait_for()` itself is cancelled it will always raise `CancelledError` regardless if the underlying task is still running. This is similar to a race with the timeout, which is handled already. --- Lib/asyncio/tasks.py | 9 ++++++--- Lib/test/test_asyncio/test_tasks.py | 16 ++++++++++++++++ .../Library/2020-08-15-15-21-40.bpo-37658.f9nivB.rst | 2 ++ 3 files changed, 24 insertions(+), 3 deletions(-) create mode 100644 Misc/NEWS.d/next/Library/2020-08-15-15-21-40.bpo-37658.f9nivB.rst diff --git a/Lib/asyncio/tasks.py b/Lib/asyncio/tasks.py index 7ecec96..8b05434 100644 --- a/Lib/asyncio/tasks.py +++ b/Lib/asyncio/tasks.py @@ -465,9 +465,12 @@ async def wait_for(fut, timeout, *, loop=None): try: await waiter except exceptions.CancelledError: - fut.remove_done_callback(cb) - fut.cancel() - raise + if fut.done(): + return fut.result() + else: + fut.remove_done_callback(cb) + fut.cancel() + raise if fut.done(): return fut.result() diff --git a/Lib/test/test_asyncio/test_tasks.py b/Lib/test/test_asyncio/test_tasks.py index 511961c..74fc1e4 100644 --- a/Lib/test/test_asyncio/test_tasks.py +++ b/Lib/test/test_asyncio/test_tasks.py @@ -1120,6 +1120,22 @@ class BaseTaskTests: res = loop.run_until_complete(task) self.assertEqual(res, "ok") + def test_wait_for_cancellation_race_condition(self): + def gen(): + yield 0.1 + yield 0.1 + yield 0.1 + yield 0.1 + + loop = self.new_test_loop(gen) + + fut = self.new_future(loop) + loop.call_later(0.1, fut.set_result, "ok") + task = loop.create_task(asyncio.wait_for(fut, timeout=1)) + loop.call_later(0.1, task.cancel) + res = loop.run_until_complete(task) + self.assertEqual(res, "ok") + def test_wait_for_waits_for_task_cancellation(self): loop = asyncio.new_event_loop() self.addCleanup(loop.close) diff --git a/Misc/NEWS.d/next/Library/2020-08-15-15-21-40.bpo-37658.f9nivB.rst b/Misc/NEWS.d/next/Library/2020-08-15-15-21-40.bpo-37658.f9nivB.rst new file mode 100644 index 0000000..694fbbb --- /dev/null +++ b/Misc/NEWS.d/next/Library/2020-08-15-15-21-40.bpo-37658.f9nivB.rst @@ -0,0 +1,2 @@ +:meth:`asyncio.wait_for` now properly handles races between cancellation of +itself and the completion of the wrapped awaitable. -- cgit v0.12