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GH-116738: document thread-safety of bisect #136555

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merged 7 commits into from
Jul 30, 2025

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@nascheme nascheme commented Jul 11, 2025

I don't think it makes sense to make these functions thread-safe. They are already unsafe when used in the default build. And, given that they can operate on any sequence object, trying to lock the sequence object doesn't make sense.

I added a unit test because I believe these functions should not crash or produce TSAN warnings when they are used on a sequence being mutated in another thread.


📚 Documentation preview 📚: https://cpython-previews--136555.org.readthedocs.build/

@nascheme nascheme added docs Documentation in the Doc dir topic-free-threading labels Jul 11, 2025
@github-project-automation github-project-automation bot moved this to Todo in Docs PRs Jul 11, 2025
@bedevere-app bedevere-app bot added the tests Tests in the Lib/test dir label Jul 11, 2025
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Possible suggestions:

  • Use a .. note:: if you think users should know about it.
  • Use a .. warning:: if you think users should be careful about it.
  • Do not use either of them if you think it's just good that users know about it (a note or a warning is quite visible in the sense that it creates a box where the entire content is inside that box).
  • Use a subsection about thread-safetiness. Or use a small warning box just saying that the functions are not thread-safe, and add a link to a section at the bottom of the page that contains more detailed explanations.

cc @hugovk

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Using "note" seems appropriate to me in this case. In the long term, I suggest it makes sense to have a thread-safety (or concurrency-safety) section for any module that has unusual rules (non-atomic functions, shared state). In the "warnings" doc, I added a "Concurrent safety of Context Managers" section to it. That's a case where the rules are quite complex and a dedicated section makes sense.

@nascheme nascheme marked this pull request as ready for review July 14, 2025 18:50
@nascheme nascheme requested a review from rhettinger as a code owner July 14, 2025 18:50
@rhettinger rhettinger removed their request for review July 15, 2025 03:17
@@ -0,0 +1,57 @@
import unittest
from test.support import import_helper, threading_helper
from threading import Thread, Barrier
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Suggested change
from threading import Thread, Barrier

this would fix lint CI

@kumaraditya303 kumaraditya303 added needs backport to 3.13 bugs and security fixes needs backport to 3.14 bugs and security fixes labels Jul 24, 2025
@nascheme nascheme enabled auto-merge (squash) July 30, 2025 02:21
@nascheme nascheme merged commit 5236b02 into python:main Jul 30, 2025
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@github-project-automation github-project-automation bot moved this from Todo to Done in Docs PRs Jul 30, 2025
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Thanks @nascheme for the PR 🌮🎉.. I'm working now to backport this PR to: 3.13, 3.14.
🐍🍒⛏🤖

miss-islington pushed a commit to miss-islington/cpython that referenced this pull request Jul 30, 2025
(cherry picked from commit 5236b02)

Co-authored-by: Neil Schemenauer <nas-github@arctrix.com>
miss-islington pushed a commit to miss-islington/cpython that referenced this pull request Jul 30, 2025
(cherry picked from commit 5236b02)

Co-authored-by: Neil Schemenauer <nas-github@arctrix.com>
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bedevere-app bot commented Jul 30, 2025

GH-137221 is a backport of this pull request to the 3.14 branch.

@bedevere-app bedevere-app bot removed the needs backport to 3.14 bugs and security fixes label Jul 30, 2025
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bedevere-app bot commented Jul 30, 2025

GH-137222 is a backport of this pull request to the 3.13 branch.

@bedevere-app bedevere-app bot removed the needs backport to 3.13 bugs and security fixes label Jul 30, 2025
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3 participants