The stepdown thread can execute the stepdown if the resumed event is cleared by the hook just after the thread ran the wait() on it. 

1. The stepdown thread checks if it has to wait: checks _is_resumed_evt which is set, so it continues
2. The hook calls pause()
   1. In pause(): the _is_resumed_evt is cleared
   2. In pause(): the hook waits on _is_idle_evt which it already set so it continues
3. The stepdown thread runs _step_down_all()