Description

assignee = None
closed_at = None
created_at = <Date 2020-01-28.13:04:56.485>
labels = ['type-bug']
title = 'multiprocessing Pool maxtasksperchild=0 raises exception with endless traceback'
updated_at = <Date 2020-01-28.13:48:42.667>
user = 'https://bugs.python.org/jeyekomon'

activity = <Date 2020-01-28.13:48:42.667>
actor = 'xtreak'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = []
creation = <Date 2020-01-28.13:04:56.485>
creator = 'jeyekomon'
dependencies = []
files = []
hgrepos = []
issue_num = 39477
keywords = []
message_count = 1.0
messages = ['360872']
nosy_count = 3.0
nosy_names = ['pitrou', 'davin', 'jeyekomon']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue39477'
versions = []

Activity

1. jeyekomon commented on Jan 28, 2020

   

   jeyekomonmannequin

   on Jan 28, 2020

   MannequinAuthor

   More actions

   The following code is expected to fail:

   import multiprocessing
   
   def f(x):
   	return x
   
   if __name__ == '__main__':
   	with multiprocessing.Pool(2, maxtasksperchild=0) as pool:
   		pool.map(f, range(3))

   since it uses a wrong value of the 'maxtasksperchild' parameter. I expect it to raise a ValueError but instead it starts to fill the stderr with practically endless traceback:

   Process ForkPoolWorker-2:
   Process ForkPoolWorker-1:
   Traceback (most recent call last):
     File "/usr/lib/python3.6/multiprocessing/process.py", line 258, in _bootstrap
       self.run()
     File "/usr/lib/python3.6/multiprocessing/process.py", line 93, in run
       self._target(*self._args, **self._kwargs)
     File "/usr/lib/python3.6/multiprocessing/pool.py", line 95, in worker
       assert maxtasks is None or (type(maxtasks) == int and maxtasks > 0)
   Traceback (most recent call last):
   AssertionError
     File "/usr/lib/python3.6/multiprocessing/process.py", line 258, in _bootstrap
       self.run()
     File "/usr/lib/python3.6/multiprocessing/process.py", line 93, in run
       self._target(*self._args, **self._kwargs)
     File "/usr/lib/python3.6/multiprocessing/pool.py", line 95, in worker
       assert maxtasks is None or (type(maxtasks) == int and maxtasks > 0)
   AssertionError
   Process ForkPoolWorker-4:
   Process ForkPoolWorker-3:
   ...

   I don't think this is expected behavior.
   Tested with Python 3.6.9 on Ubuntu 18.04.3.
2. jeyekomon

   added

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

   on Jan 28, 2020
3. ezio-melotti

   transferred this issue fromon Apr 10, 2022
4. serhiy-storchaka

   added this to Multiprocessing issueson May 20, 2022
5. iritkatriel

   added a commit that references this issue on May 30, 2022

   pythongh-83658: make multiprocessing.Pool raise an exception if maxta…

   ad25815
6. vstinner

   added

   topic-multiprocessing

   on Jun 6, 2022
7. miss-islington

   closed this as completedin #93364on Jun 17, 2022
8. miss-islington

   moved this to Done in Multiprocessing issueson Jun 17, 2022
9. miss-islington

   added 3 commits that reference this issue on Jun 17, 2022

   GH-83658: make multiprocessing.Pool raise an exception if maxtasksper…

   e37a158

   pythonGH-83658: make multiprocessing.Pool raise an exception if maxta…

   055e0eb

   pythonGH-83658: make multiprocessing.Pool raise an exception if maxta…

   a49809d
10. iritkatriel

    added 2 commits that reference this issue on Jun 17, 2022

    GH-83658: make multiprocessing.Pool raise an exception if maxtasksper…

    2b7fc1b

    GH-83658: make multiprocessing.Pool raise an exception if maxtasksper…

    2d33d21
11. serhiy-storchaka

    added a commit that references this issue on Jun 26, 2022

    Revert 30935 defer bpo45162 to 312 (#94285)

    1ffde3e

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