Description

mhsmith

opened on May 24, 2025

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Bug report

Bug description:

Android doesn't support multiprocessing because it doesn't support the System V IPC API, and iOS doesn't support subprocesses at all. However, there are a couple of things that should still work on these platforms, but currently don't:

• multiprocessing.dummy.Pool (aka multiprocessing.pool.ThreadPool) currently depends on the multiprocessing synchronization primitives, when it could use the threading equivalents instead.

• multiprocessing.synchronize throws an exception on import if the synchronization primitives are unavailable. But this breaks some packages like joblib, which imports the primitives but doesn't always use them (joblib/joblib#825).

Chaquopy has some monkey patches to work around these issues, but it would be better if they were fixed upstream.

CPython versions tested on:

CPython main branch

Operating systems tested on:

Other

Linked PRs

• gh-134634: Use a pipe instead of a queue for Pool's change notifier #148050

Activity

1. mhsmith

   added

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

   OS-ios

   OS-android

   on May 24, 2025
2. terryjreedy

   added

   type-featureA feature request or enhancementA feature request or enhancement

   and removed

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

   on May 24, 2025
3. terryjreedy commented on May 24, 2025

   

   terryjreedy

   on May 24, 2025

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   (EDIT) I have no idea is these changed would be acceptible. In any case, we cannot/will-not grab other people's code. Someone with 'ownership' of chaquopy would have to sign our Contributor Licensing Agreement and submit a PR with their code. Or someone else (you?) would have to write new code that does not violate their copyright.
4. freakboy3742 commented on May 25, 2025

   

   freakboy3742

   on May 25, 2025

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   @terryjreedy FTR: @mhsmith is the founder and principal author of Chaquopy.
5. mhsmith commented on May 25, 2025

   

   mhsmith

   on May 25, 2025

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   Yes, I've already signed the CLA, and, if the fact that it's MIT licensed isn't already sufficient, I hereby give permission for anyone to contribute Chaquopy code to CPython.

   However, a proper upstream solution will probably look a bit different to the monkey patches. I only linked to them to demonstrate that this could be fixed with a relatively small change.
6. serhiy-storchaka commented on Apr 4, 2026

   

   serhiy-storchaka

   on Apr 4, 2026

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   I agree that ThreadPool should not depend on shared memory and other IPC. But solution proposed in #148050 while simple, looks heavyweight to me. ThreadPool should not need opening named pipes.

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