RwLock needs a task-fair locking policy

[parasyte]

Because readers and writers are queued independently, read-heavy workloads will starve writers.

See parking_lot::RwLock for an example implementation that does not have this starvation problem with exclusive access.

[asomers]

Hm, you're right. I always intended to give writers priority over readers, but now that I review the code I see that I didn't actually do that. Thanks for pointing it out.