Fix mutex send #1121
Open
Fix mutex send #1121
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
Each mutex is generated uniquely for each task, it is unsound to send them between tasks. But they are `Send`. Before, it wasn't an issue, because you couldn't share non-`'static` data between them, but with \rtic-rs#1043 you can make the mutex `'static`. Thus we need to use actual tools that Rust provides and out out from `Send`. Currently, mutexes are simple ZSTs with `PhantomData<&'a ()>`, which is `Send`. We replace it with `PhantomData<(&'a (), *const u8)>`, and return `Sync` back via `unsafe` implementation. It is trivially sound, because mutexes have no method methods that accept `&self`. See https://doc.rust-lang.org/std/sync/struct.Exclusive.html for details.
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
1 participant
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Outdated suggestions cannot be applied.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.
Each mutex is generated uniquely for each task, it is unsound to send them between tasks. But they are
Send. Before, it wasn't an issue, because you couldn't share non-'staticdata between them, but with #1043 you can make the mutex'static. Thus we need to use actual tools that Rust provides and out out fromSend.Currently, mutexes are simple ZSTs with
PhantomData<&'a ()>, which isSend. We replace it withPhantomData<(&'a (), *const u8)>, and returnSyncback viaunsafeimplementation. It is trivially sound, because mutexes haveno method methods that accept
&self. See https://doc.rust-lang.org/std/sync/struct.Exclusive.html for details.