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GeezerVison is showing github.com — gh-152741: Publish thread states to the interpreter's thread list only after they are fully initialized by kumaraditya303 · Pull Request #156202 · python/cpython

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@kumaraditya303

@kumaraditya303 kumaraditya303 commented Aug 21, 2026 •
edited by bedevere-app Bot
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  • Issue: Data race between sys._current_exceptions() and a concurrently attaching thread #152741

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@kumaraditya303
pythongh-152741: Publish thread states to the interpreter's thread li…
6213ab4 
…st only after they are fully initialized
@bedevere-app bedevere-app Bot mentioned this pull request Aug 21, 2026
Data race between sys._current_exceptions() and a concurrently attaching thread #152741
Open
@kumaraditya303 kumaraditya303 added the skip news label Aug 21, 2026
@kumaraditya303
fix eval breaker version
5d1fcf7
@kumaraditya303
kumaraditya303 marked this pull request as ready for review August 22, 2026 07:50
@kumaraditya303
kumaraditya303 requested review from FFY00, ZeroIntensity and ericsnowcurrently as code owners August 22, 2026 07:50
@bedevere-app bedevere-app Bot added the awaiting core review label Aug 22, 2026
@kumaraditya303
kumaraditya303 requested a review from mpage September 9, 2026 16:11
@kumaraditya303
Merge branch 'main' into pythongh-152741-defer-tstate-publish
ea15c1d
@kumaraditya303 kumaraditya303 added the topic-free-threading label Sep 9, 2026
@ambv ambv mentioned this pull request Oct 20, 2026
gh-152741: Fix data race on PyThreadState.thread_id during thread bind #152755
Closed
@kumaraditya303
Merge remote-tracking branch 'upstream/main' into pythongh-152741-def…
5ba1e0f 
…er-tstate-publish

# Conflicts:
#	Python/pystate.c
mpage
mpage requested changes Nov 11, 2026
View reviewed changes
Comment thread Python/pystate.c
Comment on lines -1718 to -1720
// Add the new thread state to the interpreter.
PyThreadState *old_head = interp->threads.head;
add_threadstate(interp, (PyThreadState *)tstate, old_head);

@mpage mpage Nov 11, 2026

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Codex flagged that moving add_threadstate() into bind_tstate() introduces a potential use after free caused by a race with interpreter shutdown. I think it's right. Here's the race:

  1. A new daemon thread, D, is started, but something causes a delay between thread creation and when it's bound.
  2. Another thread finalizes the interpreter, but because D's thread state hasn't been inserted into the thread list, finalization doesn't see it and doesn't set its state to _Py_THREAD_SHUTTING_DOWN.
  3. D resumes. Its state is still _Py_THREAD_DETACHED so it continues normal execution and attempts to dereference tstate->interp. This results in either interacting with a finalized interpreter (the main interpreter) or freed memory (a subinterpreter).

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@bedevere-app bedevere-app Bot added awaiting changes and removed awaiting core review labels Nov 11, 2026
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bedevere-app Bot commented Nov 11, 2026

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@mpage mpage mpage requested changes
@ericsnowcurrently ericsnowcurrently Awaiting requested review from ericsnowcurrently ericsnowcurrently is a code owner
@ZeroIntensity ZeroIntensity Awaiting requested review from ZeroIntensity ZeroIntensity is a code owner
@FFY00 FFY00 Awaiting requested review from FFY00 FFY00 is a code owner

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@kumaraditya303 @mpage
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