use compare_exchange_strong to protect agianst spurious failures
#40540
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
A `compare_exchange_weak` can spuriously return false, regardless of whether a concurrent access happened. This was causing a null-pointer dereference in TaskGroupImpl::poll in a narrow circumstance. The dereference failure only appears when using the `arm64` slice of the runtime library, since Clang will use `ldxr/stxr` for synchronization on such targets. The weak form does not retry on a spurious failure, but the strong version will. resolves rdar://84192672 (cherry picked from commit 69e80a1)
|
@swift-ci please test |
|
@swift-ci test |
|
Build failed |
|
@swift-ci test macOS |
|
@swift-ci test windows |
|
@swift-ci clean test |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
5 participants
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Outdated suggestions cannot be applied.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.
A
compare_exchange_weakcan spuriously return false, regardless ofwhether a concurrent access happened. This was causing a null-pointer
dereference in TaskGroupImpl::poll in a narrow circumstance.
The dereference failure only appears when using the
arm64slice of the runtime library, since Clang will use
ldxr/stxrforsynchronization on such targets. The weak form does not retry on a
spurious failure, but the strong version will.
resolves rdar://84192672