Thread local, `!Send + !Sync` version of `Event`

[yshui]

Does it make sense to have a !Send + !Sync version of Event, to be used with LocalExecutor? Feels silly to pay the cost of thread synchronization when everything is happening on a single thread.

(and also a thread local version of Mutex and RwLock, which IIUC is based on event_listener?)

[notgull]

Previously, I was working on a thread-unsafe async framework called unsend, which had thread unsafe versions of most of smol's primitives. I stopped developing because I heard that Rust was moving towards adding !Send + !Sync versions of Waker, and if they did that it would change up my model considerably.

That being said, smol is intended to be thread-safe. Barring some kind of crazy generic solution, I don't see us moving forward on this.

[yshui]

I heard that Rust was moving towards adding !Send + !Sync versions of Waker

Do you mean this: rust-lang/libs-team#191 ?

[yshui]

smol is intended to be thread-safe.

If this is the case, maybe LocalExecutor shouldn't be included either?

[notgull]

I've released unsend version 0.1.0, with an Event structure similar to the one in this crate, but is !Sync and doesn't use any synchronization primitives.

Since we are not planning on adding an equivalent structure to EventListener, I'll close this issue now.

If this is the case, maybe LocalExecutor shouldn't be included either?

LocalExecutor is a special case I feel, because most contemporary async runtimes (even thread-safe ones) provide a LocalExecutor analogue.