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gh-159739: Preserve ContextVar cache updates from finalizers - #160197
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JelleZijlstra merged 1 commit intoOct 22, 2026
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Resetting a ContextVar can finalize the replaced value, whose finalizer may set the variable again. Updating the lookup cache after releasing the old context root overwrites that newer cached value, so get() can return a stale value or use a freed object. Update the cache before the old root can be released. Backport to 3.15 and 3.14.
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Thanks @jelle-openai for the PR, and @JelleZijlstra for merging it 🌮🎉.. I'm working now to backport this PR to: 3.14. |
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Thanks @jelle-openai for the PR, and @JelleZijlstra for merging it 🌮🎉.. I'm working now to backport this PR to: 3.15. |
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GH-160329 is a backport of this pull request to the 3.14 branch. |
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GH-160330 is a backport of this pull request to the 3.15 branch. |
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JelleZijlstra
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…H-160197) (#160329) Resetting a ContextVar can finalize the replaced value, whose finalizer may set the variable again. Updating the lookup cache after releasing the old context root overwrites that newer cached value, so get() can return a stale value or use a freed object. Update the cache before the old root can be released. Backport to 3.15 and 3.14. (cherry picked from commit f4f8b93) Co-authored-by: Jelle Zijlstra <jelle@openai.com>
JelleZijlstra
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that referenced
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Oct 22, 2026
…H-160197) (#160330) Resetting a ContextVar can finalize the replaced value, whose finalizer may set the variable again. Updating the lookup cache after releasing the old context root overwrites that newer cached value, so get() can return a stale value or use a freed object. Update the cache before the old root can be released. Backport to 3.15 and 3.14. (cherry picked from commit f4f8b93) Co-authored-by: Jelle Zijlstra <jelle@openai.com>
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Resetting a ContextVar can finalize the replaced value, whose finalizer may set the variable again. Updating the lookup cache after releasing the old context root overwrites that newer cached value, so get() can return a stale value or use a freed object. Update the cache before the old root can be released. Backport to 3.15 and 3.14.