|mp:process-wait whostate predicate &key polling-interval||[Function]|
Causes the process to wait until predicate returns true. The predicate can not call mp:process-wait. Since the predicate may be evaluated may times it should be relative fast native compiled code. This implementation retests the predicate at the polling-interval which defaults to 0.01 seconds, or when signaled by mp:process-wakeup. The single true predicate value is returned.