8000 bpo-26180: Fix multiple registration of ForkAwareLocal atfork cleaner by orivej · Pull Request #13986 · python/cpython · GitHub
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bpo-26180: Fix multiple registration of ForkAwareLocal atfork cleaner #13986

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bpo-26180: Fix multiple registration of ForkAwareLocal atfork cleaner #13986

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orivej
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8000 orivej commented Jun 11, 2019 •
edited by bedevere-bot
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threading.local instance __init__ method is called multiple times, once per
thread where the instance is used, but ForkAwareLocal atfork handler needs to be
registered just once when its instance is created. If it is registered many
times, the registrations bloat _afterfork_registry as long as the instance is
alive, and can exhaust all memory.

https://bugs.python.org/issue26180

@orivej
bpo-26180: Fix multiple registration of ForkAwareLocal atfork cleaner
adb9923 
`threading.local` instance `__init__` method is called multiple times, once per
thread where the instance is used, but ForkAwareLocal atfork handler needs to be
registered just once when its instance is created. If it is registered many
times, the registrations bloat `_afterfork_registry` as long as the instance is
alive, and can exhaust all memory.
@asvetlov
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A test for the change would be awesome

@orivej
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orivej 8000 commented Jun 11, 2019

I have added a test TestForkAwareLocal modeled (and placed) after TestForkAwareThreadLock.

@orivej
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orivej commented Jun 11, 2019

Added a NEWS blurb. Feel free to edit or squash commits as you see fit.

jdemeyer
jdemeyer approved these changes Jun 14, 2019
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The change and test look good to me. The only thing that I'm not sure about is whether this is the best fix for the problem: as I mentioned on bpo-26810 I wonder if we could ensure that __init__ is not called multiple times.

@orivej
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orivej commented Jun 14, 2019

__init__ is called multiple times by design of threading.local: https://github.com/python/cpython/blob/v3.7.3/Lib/_threading_local.py#L65-L67 . Since https://docs.python.org/3.7/library/threading.html#threading.local refers to this docstring, I guess this is a documented behaviour and changing it would be breaking.

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OK, you convinced me.

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orivej commented Jul 2, 2019

What shall happen next?

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jdemeyer commented Jul 2, 2019

We need a core developer to review your PR.

@orivej
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orivej commented Aug 3, 2019

Monthly ping.

@orivej orivej mentioned this pull request Sep 9, 2019
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@mzamazal mzamazal mannequin mentioned this pull request Apr 10, 2022
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@orivej @asvetlov @jdemeyer @the-knights-who-say-ni @ezio-melotti @bedevere-bot
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