rust-async-internals

The Rust Future poll model drives async tasks by repeatedly calling poll until it returns Ready, scheduling them again when Pending. This skill diagnoses why a tokio task never completes by explaining the poll loop, waker mechanics, and providing code-level fixes for stuck futures.

Debug async stack traces and find blocking tokio tasks by using tokio-console to inspect poll times and wake counts. This skill guides you through interpreting tokio-console output to locate long-running tasks and migrate blocking code to spawn_blocking.

Pin and Unpin manage self-referential state machines in Rust async code by preventing moved references after polling starts. This skill clarifies Pin semantics and shows safe patterns for pinning futures on the heap or stack without causing undefined behavior.

The tokio select! macro drops pending futures when one branch completes and evaluates branches in declaration order when biased. This skill diagnoses select! and join! concurrency surprises, showing when to fuse futures to prevent losing in-progress task state.

Fix a waker leak causing excessive wake-ups in Rust async code by tracing how the Waker is stored and invoked during the poll cycle. This skill provides reproduction steps and remediation examples to correct waker handling and improve tokio task latency.

Use spawn_blocking in tokio when running synchronous CPU-bound or I/O operations that would otherwise stall the async runtime. This skill explains cooperative yielding, LocalSet usage, and how to migrate blocking code without starving other async tasks.