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[3.15] gh-159739: Preserve ContextVar cache updates from finalizers (GH-160197) - #160330
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…ythonGH-160197) 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.
(cherry picked from commit f4f8b93)
Co-authored-by: Jelle Zijlstra jelle@openai.com