task waker

atomic waker

AtomicWaker is a multi-consumer, single-producer transfer cell. The cell stores a Waker value produced by calls to register and many threads can race to take the waker by calling wake.

Because of this, the task will do one of two things.

1. Observe the application state change that Thread B is waking on. In this case, it is OK for Thread B's wake to be lost.

2. Call register before attempting to observe the application state. Since Thread A still holds the wake lock, the call to register will result in the task waking itself and get scheduled again.