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gh-103758: Add test for multiple os.register_at_fork registrations - #159705

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plfj:gh-103758-fork-order

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gh-103758: Add test for multiple os.register_at_fork registrations#159705
plfj wants to merge 1 commit into
python:mainfrom
plfj:gh-103758-fork-order

plfj commented Oct 19, 2026 •

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Fixes gh-103758.
Supersedes and closes gh-103759.

Summary

Adds a regression test to Lib/test/test_os/test_posix.py to ensure multiple callbacks are handled correctly when registering multiple callbacks with os.register_at_fork().

The test ensures that:

before callbacks are called in reverse order (LIFO).
after_in_parent callbacks are called in order (FIFO).
after_in_child callbacks are called in order (FIFO).
Callbacks registered after forks will be registered and called alongside previous generations.

Notes

Original issue raised by @itsankitkp. Original code can be seen in #103759.

This PR replaces #103759 by addressing reliability concerns from the earlier attempt:

Ensures there are no race conditions between processes by verifying events correctly in memory.
Avoids deadlocks due to pipe starvation on child exit.
All children are cleaned up with test.support.wait_process and their exit status checked.
Original author noted in the commit trailer.

Checklist

Tested locally: ./python -m test -v test_os.test_posix
All CI checks passed
No NEWS entry: Test-only change (see Devguide)

python-cla-bot Bot commented Oct 19, 2026 •

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All commit authors signed the Contributor License Agreement.

bedevere-app Bot added the type-feature label

bedevere-app Bot mentioned this pull request

Add test case in os.register_at_fork to verify new and old forkers get executed #103758

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bedevere-app Bot added awaiting review tests labels

bedevere-app Bot commented Oct 19, 2026

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.

plfj force-pushed the gh-103758-fork-order branch from 5e815cc to 6f97f0a Compare

October 19, 2026 15:30

bedevere-app Bot commented Oct 19, 2026

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.

plfj force-pushed the gh-103758-fork-order branch from 6f97f0a to df98a97 Compare

October 20, 2026 10:35

bedevere-app Bot commented Oct 20, 2026

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.

plfj force-pushed the gh-103758-fork-order branch 3 times, most recently from c9d2617 to a7dd836 Compare

October 20, 2026 16:20

bedevere-app Bot commented Oct 20, 2026

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.


          pythongh-103758: Test that os.register_at_fork handlers accumulate ac…

e177458

…ross forks

Add a test verifying that handlers registered after an earlier fork()
run together with previously registered handlers in subsequent forks,
preserving LIFO order for 'before' handlers and FIFO order for 'after_*'
handlers.

Co-authored-by: Ankit Kumar Pandey <itsankitkp@users.noreply.github.com>

plfj force-pushed the gh-103758-fork-order branch from a7dd836 to e177458 Compare

October 24, 2026 17:10

bedevere-app Bot commented Oct 24, 2026

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.

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awaiting review tests type-feature