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GeezerVison is showing github.com — gh-155519: fix data-race for Context.ctx_vars by nascheme · Pull Request #155522 · python/cpython

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@nascheme

@nascheme nascheme commented Aug 10, 2026 •
edited by bedevere-app Bot
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The HAMT held by a context is immutable, but the pointer to it is not: contextvar_set() and contextvar_del() install a new HAMT and drop the reference to the previous one. Use critical sections to ensure ordering in the free-threaded build.

  • Issue: Data race with Context ctx_vars under free-threading #155519

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@nascheme
pythongh-155519: fix data-race for Context.ctx_vars
84d1261 
The HAMT held by a context is immutable, but the pointer to it is not:
contextvar_set() and contextvar_del() install a new HAMT and drop the
reference to the previous one.  Use critical sections to ensure
ordering in the free-threaded build.
@nascheme nascheme added the topic-free-threading label Aug 10, 2026
@bedevere-app bedevere-app Bot mentioned this pull request Aug 10, 2026
Data race with Context ctx_vars under free-threading #155519
Closed
@nascheme
nascheme marked this pull request as ready for review August 12, 2026 15:20
@nascheme
nascheme requested a review from 1st1 as a code owner August 12, 2026 15:20
@bedevere-app bedevere-app Bot added the awaiting core review label Aug 12, 2026
@nascheme
Reduce verbosity of comments.
3b35dfd
@nascheme
nascheme requested a review from kumaraditya303 August 12, 2026 18:54
kumaraditya303
kumaraditya303 approved these changes Aug 14, 2026
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@bedevere-app bedevere-app Bot added awaiting merge and removed awaiting core review labels Aug 14, 2026
@kumaraditya303
kumaraditya303 merged commit 9ee248c into python:main Aug 15, 2026
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@bedevere-app bedevere-app Bot removed the awaiting merge label Aug 15, 2026
@kumaraditya303 kumaraditya303 added needs backport to 3.14 bugs and security fixes needs backport to 3.15 bugs and security fixes labels Aug 16, 2026
@miss-islington-app

miss-islington-app Bot commented Aug 16, 2026

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Thanks @nascheme for the PR, and @kumaraditya303 for merging it 🌮🎉.. I'm working now to backport this PR to: 3.14.
🐍🍒⛏🤖
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@miss-islington-app

miss-islington-app Bot commented Aug 16, 2026

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Thanks @nascheme for the PR, and @kumaraditya303 for merging it 🌮🎉.. I'm working now to backport this PR to: 3.15.
🐍🍒⛏🤖
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@bedevere-app

bedevere-app Bot commented Aug 16, 2026

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GH-155892 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 Aug 16, 2026
@bedevere-app

bedevere-app Bot commented Aug 16, 2026

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GH-155893 is a backport of this pull request to the 3.15 branch.
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@bedevere-app bedevere-app Bot removed the needs backport to 3.15 bugs and security fixes label Aug 16, 2026
hugovk pushed a commit that referenced this pull request Aug 19, 2026
@miss-islington @nascheme
[3.15] gh-155519: fix data-race for Context.ctx_vars (GH-155522) (#15…
9d0e268 
…5893)

Co-authored-by: Neil Schemenauer <[email protected]>
kumaraditya303 pushed a commit that referenced this pull request Aug 20, 2026
@miss-islington @nascheme
[3.14] gh-155519: fix data-race for Context.ctx_vars (GH-155522) (#15…
8854fbc 
…5892)

gh-155519: fix data-race for Context.ctx_vars (GH-155522)
(cherry picked from commit 9ee248c)

Co-authored-by: Neil Schemenauer <[email protected]>
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@kumaraditya303 kumaraditya303 kumaraditya303 approved these changes
@1st1 1st1 Awaiting requested review from 1st1 1st1 is a code owner

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@nascheme @kumaraditya303
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