gh-132542: Set native thread ID after fork

[noamcohen97]

Since most of Python's runtime state, including thread-related data, is only consistent after PyOS_AfterFork_Child() is called, updating native_id in the after_fork handler ensures correctness and aligns with Python’s existing fork-handling mechanisms.

• Issue: threading.Thread.native_id for forking thread wrong after fork #132542

[ZeroIntensity]

Needs a blurb entry.

[bedevere-bot]

🤖 New build scheduled with the buildbot fleet by 6ebd095 🤖

Results will be shown at:

https://buildbot.python.org/all/#/grid?branch=refs%2Fpull%2F132701%2Fmerge

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

[ZeroIntensity]

LGTM

[serhiy-storchaka]

LGTM. 👍👍

[miss-islington-app]

Thanks @serhiy-storchaka for merging it 🌮🎉.. I'm working now to backport this PR to: 3.13, 3.14.
🐍🍒⛏🤖

[miss-islington-app]

Sorry, @serhiy-storchaka, I could not cleanly backport this to 3.13 due to a conflict.
Please backport using cherry_picker on command line.

cherry_picker 6b735023132a4ac9dc5b849d982104eeb1e8bdad 3.13

[bedevere-app]

3.14 branch.

[bedevere-app]

3.13 branch.

[kulikjak]

Hi, the newly added test fails on systems without native_id:

Traceback (most recent call last):
  File "<string>", line 6, in <module>
    parent_thread_native_id = threading.current_thread().native_id
                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: '_MainThread' object has no attribute 'native_id'

(while Lib/threading.py does check for its existence, the test does not)

[noamcohen97]

@kulikjak Thank you for noticing. I apologize for that.
I have created #134408 to address the issue.

@serhiy-storchaka Can you please help with merging the fix?

[kulikjak]

No worries, thanks for the fix!