New submission from Thomas Grainger <tagr...@gmail.com>:
with the following demo script I can get a IndexError: pop from empty list
```
import itertools
import asyncio
import concurrent.futures
import sys
import threading
threads = 200
def test_all_tasks_threading() -> None:
async def foo() -> None:
await asyncio.sleep(0)
async def create_tasks() -> None:
for i in range(1000):
asyncio.create_task(foo())
await asyncio.sleep(0)
results = []
with concurrent.futures.ThreadPoolExecutor(threads) as tpe:
for f in concurrent.futures.as_completed(
tpe.submit(asyncio.run, create_tasks()) for i in range(threads)
):
results.append(f.result())
assert results == [None] * threads
def main():
for i in itertools.count():
test_all_tasks_threading()
print(f"worked {i}")
return 0
if __name__ == "__main__":
sys.exit(main())
```
```
worked 0
worked 1
worked 2
worked 3
worked 4
worked 5
worked 6
worked 7
worked 8
worked 9
worked 10
worked 11
worked 12
worked 13
worked 14
worked 15
worked 16
worked 17
worked 18
Traceback (most recent call last):
File "/home/graingert/projects/asyncio-demo/demo.py", line 36, in <module>
sys.exit(main())
File "/home/graingert/projects/asyncio-demo/demo.py", line 30, in main
test_all_tasks_threading()
File "/home/graingert/projects/asyncio-demo/demo.py", line 24, in
test_all_tasks_threading
results.append(f.result())
File "/usr/lib/python3.9/concurrent/futures/_base.py", line 438, in result
return self.__get_result()
File "/usr/lib/python3.9/concurrent/futures/_base.py", line 390, in
__get_result
raise self._exception
File "/usr/lib/python3.9/concurrent/futures/thread.py", line 52, in run
result = self.fn(*self.args, **self.kwargs)
File "/usr/lib/python3.9/asyncio/runners.py", line 48, in run
loop.run_until_complete(loop.shutdown_asyncgens())
File "/usr/lib/python3.9/asyncio/base_events.py", line 621, in
run_until_complete
future = tasks.ensure_future(future, loop=self)
File "/usr/lib/python3.9/asyncio/tasks.py", line 667, in ensure_future
task = loop.create_task(coro_or_future)
File "/usr/lib/python3.9/asyncio/base_events.py", line 433, in create_task
task = tasks.Task(coro, loop=self, name=name)
File "/usr/lib/python3.9/_weakrefset.py", line 84, in add
self._commit_removals()
File "/usr/lib/python3.9/_weakrefset.py", line 57, in _commit_removals
discard(l.pop())
IndexError: pop from empty list
sys:1: RuntimeWarning: coroutine 'BaseEventLoop.shutdown_asyncgens' was never
awaited
Task was destroyed but it is pending!
task: <Task pending name='Task-74178' coro=<BaseEventLoop.shutdown_asyncgens()
running at /usr/lib/python3.9/asyncio/base_events.py:530>>
```
here's a live demo on github actions:
https://github.com/graingert/asyncio-backport/runs/3380502247#step:5:90
----------
components: asyncio
messages: 399969
nosy: asvetlov, graingert, yselivanov
priority: normal
severity: normal
status: open
title: asyncio.create_task weakrefset race condition
versions: Python 3.8, Python 3.9
_______________________________________
Python tracker <rep...@bugs.python.org>
<https://bugs.python.org/issue44962>
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