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asyncio event loop hangs if an eager task fails to start #157301
Description
Bug report
Bug description:
Repro 1 - context not a context:
import asyncio
async def child():
return 1
async def main():
asyncio.Task(child(), loop=asyncio.get_running_loop(),
eager_start=True, context=2.14)
asyncio.run(main())Actually the repro will hang, and the displayed exception is not readable and informative about what was wrong:
➜ cpython git:(main) ✗ ./python.exe repro.py
Exception in callback <_asyncio.TaskStepMethWrapper object at 0x104911ba0>()
handle: <Handle <_asyncio.TaskStepMethWrapper object at 0x104911ba0>()>
Traceback (most recent call last):
File "/Users/timofeiivankov/cpython/Lib/asyncio/events.py", line 91, in _run
self._context.run(self._callback, *self._args)
~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
RuntimeError: Invalid attempt to leave task <Task finished name='Task-1' coro=<main() done, defined at /Users/timofeiivankov/cpython/repro.py:6> exception=TypeError('an instance of Context was expected')> while task <Task pending name='Task-2' coro=<child() running at /Users/timofeiivankov/cpython/repro.py:3>> is entered.
Repro 2 - a valid Context that is already entered
import asyncio, contextvars
async def child():
return 1
async def main():
loop = asyncio.get_running_loop()
ctx = contextvars.copy_context()
ctx.run(lambda: asyncio.Task(child(), loop=loop, eager_start=True, context=ctx))
asyncio.run(main())Also hangs - type check alone doesn't cover this path
Expected behaviour: the constructor raises and the loop stays usable
TypeError: a contextvars.Context was expected, got float
Proposed fix: add type check for context, and restore the current task in the _PyContext_Enter failure branch of task_eager_start.
I have fix for this already
CPython versions tested on:
CPython main branch
Operating systems tested on:
macOS
Linked PRs
- gh-157301: Fix asyncio event loop hanging on a failed eager task start #157302
- [3.15] gh-157301: Fix asyncio event loop hanging on a failed eager task start (GH-157302) #157785
- [3.14] gh-157301: Fix asyncio event loop hanging on a failed eager task start #157844
- [3.13] gh-157301: Fix asyncio event loop hanging on a failed eager task start #157845
Activity
Merge branch 'main' into pythongh-157301-hang
gh-157301: Fix asyncio event loop hanging on a failed eager task start (
[3.15] gh-157301: Fix asyncio event loop hanging on a failed eager ta…
[3.13] gh-157301: Fix asyncio event loop hanging on a failed eager ta…