why spinlocks?

[eric-seppanen]

I haven't seen any comments or issues discussing this crate's use of spin's SpinMutex, so I though I'd open an issue to ask whether this crate could perhaps use std::sync::Mutex instead? This would simplify the dependency graph and lower cpu utilization, probably without any performance impact.

matklad's article Spinlocks Considered Harmful is good advice, I think (though the linked benchmarks are a bit out of date now).