If you join a runnable that has never been started, the join() function waits for the runnable to start and complete. If you join a runnable that is currently inactive, but has already been started previously, the join() function returns immediately. To wait for the next completion on a runnable that has already completed one or more executions, you need to delay until after the runnable has been restarted, as indicated by the RW_THR_STARTING execution state or by a completion state of RW_THR_PENDING.