wasmtime: add EngineWeak which has ::upgrade, created by Engine::weak #7797
Conversation
This file contains 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
Engine is, internally, just an Arc<EngineInner>, so this is trivial to implement - EngineWeak is a Weak<EngineInner>. This behavior is desirable because `Engine::increment_epoch` typically happens in a worker thread, which in turn requires additional machinery to discard the `Engine` once it is no longer needed. If instead the worker thread holds an `EngineWeak`, it can stop ticking when all consumers of the `Engine` have dropped it. This has been documented as a suggestion in `increment_epoch`. For an example of additional machinery which is simplified by this change, see https://github.com/fastly/Viceroy/blob/25edee0700ec0b20b1b56db0a3a8d6f090397b3a/lib/src/execute.rs#L108-L116) Co-authored-by: John Van Enk <vanenkj@gmail.com>
fitzgen
approved these changes
Jan 19, 2024
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Outdated suggestions cannot be applied.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.
Engine is, internally, just an Arc, so this is trivial to implement - EngineWeak is a Weak.
This behavior is desirable because
Engine::increment_epochtypically happens in a worker thread, which in turn requires additional machinery to discard theEngineonce it is no longer needed. If instead the worker thread holds anEngineWeak, it can stop ticking when all consumers of theEnginehave dropped it. This has been documented as a suggestion inincrement_epoch.For an example of additional machinery which is simplified by this change, see https://github.com/fastly/Viceroy/blob/25edee0700ec0b20b1b56db0a3a8d6f090397b3a/lib/src/execute.rs#L108-L116)