[issue32576] concurrent.futures.thread potential deadlock due to Queue in weakref callback

[Mark Dickinson]

Mark Dickinson  added the comment:

See also https://bugs.python.org/issue21009

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nosy: +mark.dickinson

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[issue32576] concurrent.futures.thread potential deadlock due to Queue in weakref callback

[Antoine Pitrou]

Change by Antoine Pitrou :


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keywords: +patch
pull_requests: +5069
stage: needs patch -> patch review

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[issue32576] concurrent.futures.thread potential deadlock due to Queue in weakref callback

[Antoine Pitrou]

Antoine Pitrou  added the comment:

We could also switch multiprocessing.Pool.  Unfortunately some code in 
multiprocessing.Pool relies on internal details of queue.Queue (!).

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[issue32576] concurrent.futures.thread potential deadlock due to Queue in weakref callback

[Gregory P. Smith]

New submission from Gregory P. Smith :

As a follow up to https://bugs.python.org/issue14976 which just introduced 
queue.SimpleQueue:

concurrent.futures.thread currently uses a queue.Queue() from weakref callbacks 
which could in theory lead to a deadlock when periodic gc triggers a cleanup 
invalidating some weakrefed objects at an inopportune time while Python code 
has the queue's lock held.

I don't have a test case proving this (deadlocks are hard).

Switching it to use a SimpleQueue should avoid the problem?

...

This and the C extension module based SimpleQueue would be good to backport to 
https://pypi.python.org/pypi/futures as well.

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messages: 310124
nosy: gregory.p.smith, pitrou
priority: normal
severity: normal
stage: needs patch
status: open
title: concurrent.futures.thread potential deadlock due to Queue in weakref 
callback
type: behavior
versions: Python 3.7

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