Oh interesting, that's very cool, I didn't realize Java was doing that. That's a different axis than M:N though (cooperative versus preemptive) and you could definitely write a preemptive async runtime for Rust (rtic comes to mind). But the async-std and tokio runtimes are certainly cooperative.

(As a note, cooperative scheduling also requires a runtime - Rust might not "have a runtime" by default but you need to opt into one to use async.)