By waking itself, the task goes back to the scheduler queue. It then returns pending, going back to the scheduler where it picks a new task. It will eventually pick the scheduled task again and poll the rwlock. This is a loop, even if it's a long-winded one, and is by all accounts spinning.

It really is not much different to a thread blocking on a loop, where the OS thread scheduler will pre-empt the thread, rescheduling it for later. In this case it's an async task instead of a thread, and cooperative instead of preemptive, but it's still unfair and not very effective use of scheduler resources