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GeezerVison is showing github.com — gh-116738: Test re module for free threading by yoney · Pull Request #141923 · python/cpython

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@yoney

@yoney yoney commented Nov 24, 2025 •
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  • Added atomic operations to scanner_begin() and scanner_end() to prevent race conditions on the executing flag in free-threaded builds.
  • Added tests for concurrent usage of the re module.

Without the atomic operations, test_scanner_concurrent_access() triggers assert(self->executing) failures, or a thread sanitizer run emits errors.

cc: @mpage @colesbury

  • Issue: Audit all built-in modules for thread safety #116738

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@yoney
pythongh-116738: Test re module for free threading
81a459c
@bedevere-app bedevere-app Bot mentioned this pull request Nov 24, 2025
Audit all built-in modules for thread safety #116738
Open
@yoney
yoney marked this pull request as ready for review November 24, 2025 22:23
@bedevere-app bedevere-app Bot added the awaiting review label Nov 24, 2025
colesbury
colesbury reviewed Nov 24, 2025
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I'd be inclined to include a NEWS entry. It can be something like:

Make the :func:`re.finditer` reentrancy detection thread-safe.

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Comment thread Modules/_sre/sre.c Resolved

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Comment thread Modules/_sre/sre.c Resolved

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@yoney
Replace critical sections with atomic operations
4c1e940
@yoney

yoney commented Nov 25, 2025

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@colesbury Thank you for the review. I have updated the code to use atomics.
(I re-ran the tests under tsan build after the update.)
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colesbury
colesbury approved these changes Nov 26, 2025
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Thanks!

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@bedevere-app bedevere-app Bot added awaiting merge and removed awaiting review labels Nov 26, 2025
@colesbury
colesbury merged commit bc9e63d into python:main Nov 26, 2025
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@bedevere-app bedevere-app Bot removed the awaiting merge label Nov 26, 2025
@colesbury colesbury added the needs backport to 3.14 bugs and security fixes label Nov 26, 2025
@miss-islington-app

miss-islington-app Bot commented Nov 26, 2025

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Thanks @yoney for the PR, and @colesbury for merging it 🌮🎉.. I'm working now to backport this PR to: 3.14.
🐍🍒⛏🤖
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miss-islington pushed a commit to miss-islington/cpython that referenced this pull request Nov 26, 2025
@yoney @miss-islington
pythongh-116738: Fix thread-safety issue in re module for free thread…
c8cff69 
…ing (pythongh-141923)

Added atomic operations to `scanner_begin()` and `scanner_end()` to prevent
race conditions on the `executing` flag in free-threaded builds. Also added
tests for concurrent usage of the `re` module.

Without the atomic operations, `test_scanner_concurrent_access()` triggers
`assert(self->executing)` failures, or a thread sanitizer run emits errors.
(cherry picked from commit bc9e63d)

Co-authored-by: Alper <[email protected]>
@bedevere-app

bedevere-app Bot commented Nov 26, 2025

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GH-141990 is a backport of this pull request to the 3.14 branch.
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@bedevere-app bedevere-app Bot removed the needs backport to 3.14 bugs and security fixes label Nov 26, 2025
colesbury pushed a commit that referenced this pull request Nov 26, 2025
@miss-islington @yoney
[3.14] gh-116738: Fix thread-safety issue in re module for free threa…
f47e928 
…ding (gh-141923) (gh-141990)

Added atomic operations to `scanner_begin()` and `scanner_end()` to prevent
race conditions on the `executing` flag in free-threaded builds. Also added
tests for concurrent usage of the `re` module.

Without the atomic operations, `test_scanner_concurrent_access()` triggers
`assert(self->executing)` failures, or a thread sanitizer run emits errors.
(cherry picked from commit bc9e63d)

Co-authored-by: Alper <[email protected]>
StanFromIreland pushed a commit to StanFromIreland/cpython that referenced this pull request Dec 6, 2025
@yoney @StanFromIreland
pythongh-116738: Fix thread-safety issue in re module for free thread…
bb957eb 
…ing (pythongh-141923)

Added atomic operations to `scanner_begin()` and `scanner_end()` to prevent
race conditions on the `executing` flag in free-threaded builds. Also added
tests for concurrent usage of the `re` module.

Without the atomic operations, `test_scanner_concurrent_access()` triggers
`assert(self->executing)` failures, or a thread sanitizer run emits errors.
@yoney
yoney deleted the ft_sre branch January 27, 2026 17:07
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@colesbury colesbury colesbury approved these changes

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2 participants

@yoney @colesbury
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