[5.6] Fix priority inversions when waiting on a task status lock #40594
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
The existing uses of AWQ don't need arguments during construction, but uses that do almost certainly need to update existing instances if createQueue happens to re-use one. Users probably aren't going to think about this proactively by doing something wild like reading the documentation. We can point this mistake out to them by making their code not compile if they call createQueue with arguments without providing a special method. This pattern also makes the actual update code much easier to write, since callers don't need to specially detect this case.
Add a tryReloadAndWait method to Worker (which can only be used when not the worker thread). Revise the docs to describe this sort of pattern as the more standard pattern, which I think is likely to better reflect common use.
Since locking the task status is a presumed-uncommon case, the trade-offs inherent in the allocation patterns of AtomicWaitQueue are very appropriate here, even more than they are for metadata completion. rdar://86100232
|
@swift-ci Please test |
|
Build failed |
|
LLDB test failure seems unrelated. @swift-ci Please smoke test OS X |
|
@swift-ci Please test macOS |
|
Build failed |
|
@swift-ci Please test macOS |
DougGregor
approved these changes
Dec 18, 2021
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Outdated suggestions cannot be applied.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.
Since locking the task status is a presumed-uncommon case, the trade-offs inherent in the allocation patterns of AtomicWaitQueue are very appropriate here, even more than they are for metadata completion.
rdar://86100232
5.6 version of #40586
Reviewed by Mike Ash