> your program may deadlock non-deterministically This was always true, even prior to async. Rust's thread safety features have never prevented deadlocks. They

> your program may deadlock non-deterministically This was always true, even prior to async. Rust's thread safety features have never prevented deadlocks. They prevent races, but not deadlocks. RAII makes some patterns that can cause deadlock more avoidable. Nothing in Rust prevents you from spawning a thread that locks a mutex and then never gives it up.