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ProactorEventLoop ignores Ctrl+C after closing unrelated loop #91170
Description
| BPO | 47014 |
|---|---|
| Nosy | @asvetlov, @1st1, @mhils |
| Files |
Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.
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GitHub fields:
assignee = None
closed_at = <Date 2022-03-23.21:49:14.208>
created_at = <Date 2022-03-14.17:14:47.999>
labels = ['type-bug', '3.10', 'expert-asyncio']
title = 'ProactorEventLoop ignores Ctrl+C after closing unrelated loop'
updated_at = <Date 2022-03-23.21:49:14.207>
user = 'https://github.com/mhils'bugs.python.org fields:
activity = <Date 2022-03-23.21:49:14.207>
actor = 'asvetlov'
assignee = 'none'
closed = True
closed_date = <Date 2022-03-23.21:49:14.208>
closer = 'asvetlov'
components = ['asyncio']
creation = <Date 2022-03-14.17:14:47.999>
creator = 'mhils'
dependencies = []
files = ['50675']
hgrepos = []
issue_num = 47014
keywords = []
message_count = 2.0
messages = ['415169', '415200']
nosy_count = 3.0
nosy_names = ['asvetlov', 'yselivanov', 'mhils']
pr_nums = []
priority = 'normal'
resolution = 'wont fix'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue47014'
versions = ['Python 3.10']
Activity
mhils commentedon Mar 14, 2022
When a (second) ProactorEventLoop is garbage-collected, the current ProactorEventLoop starts to ignore Ctrl+C on Windows until it is woken up. The attached repro shows a minimal example. Uncommenting the
create_taskcall or not using a second event loop fixes the behavior.I couldn't find any shared/global objects in asyncio/windows_events.py, so I'm not sure what is causing this, or why the wakeup task helps.
FWIW, the second event loop in our code base originated from a stray
get_event_loop()call, one more example that speaks in favor ofget_running_loop()!asvetlov commentedon Mar 14, 2022
Ctrl-C handling is added by bpo-23057
It uses signal.set_wakeup_fd() https://github.com/asvetlov/cpython/blob/main/Lib/asyncio/proactor_events.py#L631-L634
So, the last event loop steals Ctrl+C handling.
Not sure if we can improve it.
Running two concurrent loops in the same thread is a bad idea for many reasons. Ctrl+C is not the only reason.