gh-134381: Improve thread safety in _PyThread_AfterFork by preserving not-started handles by zangjiucheng · Pull Request #134514 · python/cpython

zangjiucheng · 2025-05-22T14:37:24Z

Issue: Not able to start an instantiated Thread in a child process through multiprocessing.Process in python 3.13 #134381

…d handles

python-cla-bot · 2025-05-22T14:37:29Z

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bedevere-app · 2025-05-22T14:37:31Z

Most changes to Python require a NEWS entry. Add one using the blurb_it web app or the blurb command-line tool.

If this change has little impact on Python users, wait for a maintainer to apply the skip news label instead.

ZeroIntensity

Could you add a test for this? Something like the repro in the issue is probably fine.

Misc/NEWS.d/next/Core_and_Builtins/2025-05-22-14-48-19.gh-issue-134381.2BXhth.rst

zangjiucheng · 2025-05-22T16:09:07Z

Could you add a test for this? Something like the repro in the issue is probably fine.

I did add a similar test case, but not sure if that's good enough to cover the issue similar to the issue mentioned. Please take a review.

Modules/_threadmodule.c

Lib/test/test_thread.py

colesbury

Tests looks good. Some comments about how to structure it in the multiprocessing test suite below.

Lib/test/_test_multiprocessing.py

colesbury

Thanks for the fix, LGTM

bedevere-bot · 2025-05-23T17:12:43Z

🤖 New build scheduled with the buildbot fleet by @colesbury for commit ca06d61 🤖

Results will be shown at:

https://buildbot.python.org/all/#/grid?branch=refs%2Fpull%2F134514%2Fmerge

If you want to schedule another build, you need to add the 🔨 test-with-refleak-buildbots label again.

ZeroIntensity

Tiny little formatting suggestion.

Modules/_threadmodule.c

miss-islington-app · 2025-05-23T19:22:18Z

Thanks @zangjiucheng for the PR, and @colesbury for merging it 🌮🎉.. I'm working now to backport this PR to: 3.13, 3.14.
🐍🍒⛏🤖

…d after fork (pythongh-134514) (cherry picked from commit 9a2346d) Co-authored-by: Jiucheng(Oliver) <git.jiucheng@gmail.com>

bedevere-app · 2025-05-23T19:22:28Z

GH-134596 is a backport of this pull request to the 3.14 branch.

bedevere-app · 2025-05-23T19:22:32Z

GH-134597 is a backport of this pull request to the 3.13 branch.

…ad after fork (gh-134514) (gh-134597) (cherry picked from commit 9a2346d) Co-authored-by: Jiucheng(Oliver) <git.jiucheng@gmail.com>

…ad after fork (gh-134514) (gh-134596) (cherry picked from commit 9a2346d) Co-authored-by: Jiucheng(Oliver) <git.jiucheng@gmail.com>

…d after fork (pythongh-134514)

Improve thread safety in _PyThread_AfterFork by preserving not-starte…

c20f566

…d handles

bedevere-app bot mentioned this pull request May 22, 2025

Not able to start an instantiated Thread in a child process through multiprocessing.Process in python 3.13 #134381

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bedevere-app bot added the awaiting review label May 22, 2025

📜🤖 Added by blurb_it.

c144379

ZeroIntensity reviewed May 22, 2025

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Misc/NEWS.d/next/Core_and_Builtins/2025-05-22-14-48-19.gh-issue-134381.2BXhth.rst Outdated Show resolved Hide resolved

Add a test case, and improve the NEWS.d

40da262

Rearrage test location, skip fork test on windows

be1f512

colesbury reviewed May 22, 2025

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colesbury added needs backport to 3.13 bugs and security fixes needs backport to 3.14 bugs and security fixes labels May 22, 2025

Enhance comment message, recreate test scenario in _test_multiprocessing

9c8f303

zangjiucheng requested a review from gpshead as a code owner May 22, 2025 22:58

zangjiucheng requested review from ZeroIntensity and colesbury May 22, 2025 23:19

colesbury reviewed May 23, 2025

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zangjiucheng added 2 commits May 23, 2025 00:01

Enhance test case setup, skip if get_start_method() is not set to 'fork'

5e0158c

Merge branch 'main' into pythongh-134381-main

ca06d61

colesbury approved these changes May 23, 2025

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bedevere-app bot added awaiting merge and removed awaiting review labels May 23, 2025

colesbury added the 🔨 test-with-refleak-buildbots Test PR w/ refleak buildbots; report in status section label May 23, 2025

bedevere-bot removed the 🔨 test-with-refleak-buildbots Test PR w/ refleak buildbots; report in status section label May 23, 2025

colesbury self-assigned this May 23, 2025

ZeroIntensity approved these changes May 23, 2025

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Addressed formatting

9827b43

colesbury merged commit 9a2346d into python:main May 23, 2025
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bedevere-app bot removed the awaiting merge label May 23, 2025

bedevere-app bot removed the needs backport to 3.14 bugs and security fixes label May 23, 2025

bedevere-app bot removed the needs backport to 3.13 bugs and security fixes label May 23, 2025

colesbury pushed a commit that referenced this pull request May 23, 2025

[3.13] gh-134381: Fix RuntimeError when starting not-yet started Thre…

e4c4ecc

…ad after fork (gh-134514) (gh-134597) (cherry picked from commit 9a2346d) Co-authored-by: Jiucheng(Oliver) <git.jiucheng@gmail.com>

colesbury pushed a commit that referenced this pull request May 23, 2025

[3.14] gh-134381: Fix RuntimeError when starting not-yet started Thre…

09a34f1

…ad after fork (gh-134514) (gh-134596) (cherry picked from commit 9a2346d) Co-authored-by: Jiucheng(Oliver) <git.jiucheng@gmail.com>

Pranjal095 pushed a commit to Pranjal095/cpython that referenced this pull request Jul 12, 2025

pythongh-134381: Fix RuntimeError when starting not-yet started Threa…

1dc1b72

…d after fork (pythongh-134514)

taegyunkim pushed a commit to taegyunkim/cpython that referenced this pull request Aug 4, 2025

pythongh-134381: Fix RuntimeError when starting not-yet started Threa…

1261548

…d after fork (pythongh-134514)

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