How to enable Mutex/Rwlock guard span?

[MrCroxx]

When I am diagnosing deadlock issue in my application, I'd to print lock guard span logs.

I found there's resource_span field in the guards of Mutex and RwLock with #[cfg(all(tokio_unstable, feature = "tracing"))] attribute. And I built my application with RUSTFLAGS="--cfg tokio_unstable" and enabled tracing feature of tokio. Then run my appliaction with RUST_LOG=trace. But I still got no logs of tokio mutex/rwlock.

Did I miss something? Could tokio user enable mutex/rwlock guard span?

(Plus, is there any better way to detect deadlock with tokio? parking_lot has deadlock feature to detect deadlock. Will tokio has the feature in future?

[MrCroxx]

I retried in a brand-new project and that works. Seems I didn't configure my subscriber right in the origin project.

[Darksonn]

Unfortunately, detecting deadlocks is not as easy with async locks as it is for something like parking_lot. There could be things like a tokio::select! that the lock doesn't know about, but which can resolve the deadlock by cancelling a call to lock.