gh-132917: Fix data race detected by tsan #133508
Merged
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
(https://github.com/python/cpython/actions/runs/14857021107/job/41712717208?pr=133502): young.count can be modified by other threads even while the gcstate is locked. This is the simplest fix to (potentially) unblock beta 1, although this particular code path seems like it could just be an atomic swap followed by an atomic add, without having the lock at all.
|
Looks okay to me. |
|
I think the mutex is still needed to reliably update deferred_count. E.g. this interleaving loses the count value. T1: read and zero count, young_count = non zero |
|
Well, that's why I suggested a swap and an add :) T1: read and zero count, young_count = non zero The two sequential operations probably aren't noticeably faster than the locking though. |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Fix data race detected by tsan (https://github.com/python/cpython/actions/runs/14857021107/job/41712717208?pr=133502): young.count can be modified by other threads even while the gcstate is locked.
This is the simplest fix to (potentially) unblock beta 1, although this particular code path seems like it could just be an atomic swap followed by an atomic add, without having the lock at all.