Description

assignee = None
closed_at = None
created_at = <Date 2021-04-19.18:36:19.433>
labels = ['type-bug', '3.8']
title = 'Deadlock when mixing event loops and subprocesses'
updated_at = <Date 2021-04-19.18:36:19.433>
user = 'https://github.com/ehrmann'

activity = <Date 2021-04-19.18:36:19.433>
actor = 'thomas'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = []
creation = <Date 2021-04-19.18:36:19.433>
creator = 'thomas'
dependencies = []
files = ['49967']
hgrepos = []
issue_num = 43890
keywords = []
message_count = 1.0
messages = ['391386']
nosy_count = 1.0
nosy_names = ['thomas']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue43890'
versions = ['Python 3.8']

Activity

1. ehrmann commented on Apr 19, 2021

   

   ehrmannmannequin

   on Apr 19, 2021

   MannequinAuthor

   More actions

   When mixing code that spawns subprocesses with code that creates event loops, Python appears to deadlock.

   In the attached example, when WORKERS = 16 and ASYNC_WORKERS = 8, Python will sometimes (50% of the time?) deadlock, never exiting, with no exceptions raised. Oddly, if ASYNC_WORKERS is set to 0 or 16 (i.e., only subprocesses or only event loops), it runs reliably.

   I tested this in an x86_64 Ubuntu 20.04.2 VM with Python 3.8.6. I was only able to reproduce it when the VM had more than one CPU, and I was unable to reproduce it on x86_64 MacOS.
2. ehrmann

   added

   3.8 (EOL)end of lifeend of life

   type-bugAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error

   on Apr 19, 2021
3. ezio-melotti

   transferred this issue fromon Apr 10, 2022
4. kumaraditya303

   added

   3.11only security fixesonly security fixes

   3.10 (EOL)end of lifeend of life

   3.9 (EOL)end of lifeend of life

   and removed

   3.8 (EOL)end of lifeend of life

   on Apr 16, 2022
5. kumaraditya303 commented on Apr 16, 2022

   

   kumaraditya303

   on Apr 16, 2022

   Contributor

   More actions

   Reproduced on 3.11, I think it is because of fork
6. AlexWaygood

   added

   topic-asyncio

   on Apr 16, 2022
7. kumaraditya303 commented on Apr 16, 2022

   

   kumaraditya303

   on Apr 16, 2022

   Contributor

   More actions

   Duplicate of #90368

   So after some investigation, this issue is a duplicate of #90368 and if you remove the print calls it is fixed. Moreover the fix in #30310 fixes this issue so closing as duplicate.
8. kumaraditya303

   closed this as completedon Apr 16, 2022

Issue actions