Benches look promising! My main concern is validating correctness; implementing good concurrency primitives is always challenging. Have you looked into testing against a purpose-built concurrency model checker like tokio-rs/loom [1] or awslabs/shuttle [2]? IMO that would go a long way towards building trust in this impl.
[1] https://github.com/tokio-rs/loom [2] https://github.com/awslabs/shuttle