Nothing so fancy.

Each worker thread runs in a loop executing a queue of jobs. On every iteration it sets an atomic progress flag to true.

The runtime in which it's contained polls its workers every 1-10ms, atomically swapping in false and checking to see if the previous value was also false - if so, it steals its task queue and spins up another worker to execute it.

https://github.com/async-rs/async-std/blob/ceba324bef9641d61...