[issue36456] task.cancel unbound recursion if task is deadlocked

[Dima Tisnek]

Change by Dima Tisnek :


--
title: task.cancel unbound recursion -> task.cancel unbound recursion if task 
is deadlocked

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue36456] task.cancel unbound recursion

[Dima Tisnek]

Dima Tisnek  added the comment:

Py3.10: tested on v3.10.0a3:8bae2a958e and v3.10.0a4:445f7f54b1

--
versions: +Python 3.10

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue36456] task.cancel unbound recursion

[Chris Jerdonek]

Change by Chris Jerdonek :


--
nosy: +chris.jerdonek

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue36456] task.cancel unbound recursion

[Guido Imperiale]

Change by Guido Imperiale :


--
nosy: +crusaderky

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue36456] task.cancel unbound recursion

[Dima Tisnek]

New submission from Dima Tisnek :

Cancelling a deadlocked group of tasks results in MaximumRecursionError

Inspired by 
https://stackoverflow.com/questions/55341189/handling-asyncio-deadlocks

Given the following test-asyncio.py:

```
import asyncio


async def test():
async def f():
await g_task

async def g():
await f_task

f_task = asyncio.create_task(f())
g_task = asyncio.create_task(g())

async def release():
await asyncio.sleep(5)
f_task.cancel()

await asyncio.gather(f_task, g_task, release())

asyncio.run(test())
```

Results in:

```
Traceback (most recent call last):
  File ".../python3.8/asyncio/runners.py", line 43, in run
return loop.run_until_complete(main)
  File ".../python3.8/asyncio/base_events.py", line 589, in run_until_complete
return future.result()
  File "test-asyncio.py", line 18, in test
await asyncio.gather(f_task, g_task, release())
  File "test-asyncio.py", line 16, in release
f_task.cancel()
RecursionError: maximum recursion depth exceeded while calling a Python object

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "test-asyncio.py", line 20, in 
asyncio.run(test())
  File ".../python3.8/asyncio/runners.py", line 46, in run
_cancel_all_tasks(loop)
  File ".../python3.8/asyncio/runners.py", line 59, in _cancel_all_tasks
task.cancel()
RecursionError: maximum recursion depth exceeded while calling a Python object
Exception in default exception handler
Traceback (most recent call last):
  File ".../python3.8/asyncio/base_events.py", line 1644, in 
call_exception_handler
self.default_exception_handler(context)
  File ".../python3.8/asyncio/base_events.py", line 1615, in 
default_exception_handler
value = repr(value)
  File ".../python3.8/asyncio/base_tasks.py", line 21, in _task_repr_info
info.insert(3, f'wait_for={task._fut_waiter!r}')
  File ".../python3.8/asyncio/base_tasks.py", line 21, in _task_repr_info
info.insert(3, f'wait_for={task._fut_waiter!r}')
  File ".../python3.8/asyncio/base_tasks.py", line 21, in _task_repr_info
info.insert(3, f'wait_for={task._fut_waiter!r}')
  [Previous line repeated 326 more times]
  File ".../python3.8/asyncio/base_tasks.py", line 9, in _task_repr_info
info = base_futures._future_repr_info(task)
  File ".../python3.8/asyncio/base_futures.py", line 57, in _future_repr_info
info.append(_format_callbacks(future._callbacks))
  File ".../python3.8/asyncio/base_futures.py", line 36, in _format_callbacks
cb = '{}, {}'.format(format_cb(cb[0][0]), format_cb(cb[1][0]))
  File ".../python3.8/asyncio/base_futures.py", line 31, in format_cb
return format_helpers._format_callback_source(callback, ())
  File ".../python3.8/asyncio/format_helpers.py", line 23, in 
_format_callback_source
func_repr = _format_callback(func, args, None)
  File ".../python3.8/asyncio/format_helpers.py", line 56, in _format_callback
func_repr += _format_args_and_kwargs(args, kwargs)
  File ".../python3.8/asyncio/format_helpers.py", line 41, in 
_format_args_and_kwargs
return '({})'.format(', '.join(items))
RecursionError: maximum recursion depth exceeded while calling a Python object
Exception in default exception handler
Traceback (most recent call last):
  File ".../python3.8/asyncio/base_events.py", line 1644, in 
call_exception_handler
self.default_exception_handler(context)
  File ".../python3.8/asyncio/base_events.py", line 1615, in 
default_exception_handler
value = repr(value)
  File ".../python3.8/asyncio/base_tasks.py", line 21, in _task_repr_info
info.insert(3, f'wait_for={task._fut_waiter!r}')
  File ".../python3.8/asyncio/base_tasks.py", line 21, in _task_repr_info
info.insert(3, f'wait_for={task._fut_waiter!r}')
  File ".../python3.8/asyncio/base_tasks.py", line 21, in _task_repr_info
info.insert(3, f'wait_for={task._fut_waiter!r}')
  [Previous line repeated 326 more times]
  File ".../python3.8/asyncio/base_tasks.py", line 9, in _task_repr_info
info = base_futures._future_repr_info(task)
  File ".../python3.8/asyncio/base_futures.py", line 57, in _future_repr_info
info.append(_format_callbacks(future._callbacks))
  File ".../python3.8/asyncio/base_futures.py", line 36, in _format_callbacks
cb = '{}, {}'.format(format_cb(cb[0][0]), format_cb(cb[1][0]))
  File ".../python3.8/asyncio/base_futures.py", line 31, in format_cb
return format_helpers._format_callback_source(callback, ())
  File ".../python3.8/asyncio/format_helpers.py", line 23, in 
_format_callback_source
func_repr = _format_callback(func, args, None)
  File ".../python3.8/asyncio/format_helpers.py", line 56, in _format_callback
func_repr += _format_args_and_kwargs(args, kwargs)
  File ".../python3.8/asyncio/format_helpers.py", line 41, in 
_format_args_and_kwargs
return '({})'.format(', '.join(items))
RecursionError: maximum recursion depth exceeded while