[Python-checkins] bpo-37658: Actually return result in race condition (GH-29202)
asvetlov
webhook-mailer at python.org
Mon Nov 29 03:13:14 EST 2021
https://github.com/python/cpython/commit/934a82623793e9d52b85f74d5395d65927a52205
commit: 934a82623793e9d52b85f74d5395d65927a52205
branch: main
author: Sam Bull <aa6bs0 at sambull.org>
committer: asvetlov <andrew.svetlov at gmail.com>
date: 2021-11-29T10:12:57+02:00
summary:
bpo-37658: Actually return result in race condition (GH-29202)
files:
A Misc/NEWS.d/next/Library/2021-11-28-15-30-34.bpo-37658.8Hno7d.rst
M Lib/asyncio/tasks.py
M Lib/test/test_asyncio/test_tasks.py
diff --git a/Lib/asyncio/tasks.py b/Lib/asyncio/tasks.py
index 9a9d0d6e3cc26..53eef84427be1 100644
--- a/Lib/asyncio/tasks.py
+++ b/Lib/asyncio/tasks.py
@@ -415,11 +415,9 @@ async def wait_for(fut, timeout):
await _cancel_and_wait(fut, loop=loop)
try:
- fut.result()
+ return fut.result()
except exceptions.CancelledError as exc:
raise exceptions.TimeoutError() from exc
- else:
- raise exceptions.TimeoutError()
waiter = loop.create_future()
timeout_handle = loop.call_later(timeout, _release_waiter, waiter)
@@ -455,11 +453,9 @@ async def wait_for(fut, timeout):
# exception, we should re-raise it
# See https://bugs.python.org/issue40607
try:
- fut.result()
+ return fut.result()
except exceptions.CancelledError as exc:
raise exceptions.TimeoutError() from exc
- else:
- raise exceptions.TimeoutError()
finally:
timeout_handle.cancel()
diff --git a/Lib/test/test_asyncio/test_tasks.py b/Lib/test/test_asyncio/test_tasks.py
index 362fbf8df08ca..a88cb89e4e6ee 100644
--- a/Lib/test/test_asyncio/test_tasks.py
+++ b/Lib/test/test_asyncio/test_tasks.py
@@ -1009,20 +1009,16 @@ def gen():
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
+ async def inner():
+ with contextlib.suppress(asyncio.CancelledError):
+ await asyncio.sleep(1)
+ return 1
- loop = self.new_test_loop(gen)
+ async def main():
+ result = await asyncio.wait_for(inner(), timeout=.01)
+ assert result == 1
- 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")
+ asyncio.run(main())
def test_wait_for_waits_for_task_cancellation(self):
loop = asyncio.new_event_loop()
@@ -1101,24 +1097,6 @@ async def inner():
with self.assertRaises(FooException):
loop.run_until_complete(foo())
- def test_wait_for_raises_timeout_error_if_returned_during_cancellation(self):
- loop = asyncio.new_event_loop()
- self.addCleanup(loop.close)
-
- async def foo():
- async def inner():
- try:
- await asyncio.sleep(0.2)
- except asyncio.CancelledError:
- return 42
-
- inner_task = self.new_task(loop, inner())
-
- await asyncio.wait_for(inner_task, timeout=_EPSILON)
-
- with self.assertRaises(asyncio.TimeoutError):
- loop.run_until_complete(foo())
-
def test_wait_for_self_cancellation(self):
loop = asyncio.new_event_loop()
self.addCleanup(loop.close)
diff --git a/Misc/NEWS.d/next/Library/2021-11-28-15-30-34.bpo-37658.8Hno7d.rst b/Misc/NEWS.d/next/Library/2021-11-28-15-30-34.bpo-37658.8Hno7d.rst
new file mode 100644
index 0000000000000..97d1e961ac2be
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2021-11-28-15-30-34.bpo-37658.8Hno7d.rst
@@ -0,0 +1,3 @@
+Fix issue when on certain conditions ``asyncio.wait_for()`` may allow a
+coroutine to complete successfully, but fail to return the result,
+potentially causing memory leaks or other issues.
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