[issue21009] Potential deadlock in concurrent futures when garbage collection occurs during Queue.get

[Simon Jagoe]

Simon Jagoe added the comment:

In the script attached to the original issue, the weakref callback that causes the hang is the callback defined in ThreadPoolExecutor._adjust_thread_count

Attached is a faulthandler stack captured from Python 3.6.1. The script submitted here uses a patched queue.get() method to force garbage collection to reliably trigger the issue, but this deadlock was observed in a real application using threadpool executors.

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Added file: https://bugs.python.org/file47132/executor-hang-faulthandler.txt

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue21009>
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