public synchronized boolean suspendIfNotReady(Procedure proc) {
    if (!ready) {
      suspendedProcedures.addLast(proc);
    }
    return !ready;
  }
Returns true if event is not ready and adds procedure to suspended queue, else returns false.
hbase-procedure/src/main/java/org/apache/hadoop/hbase/procedure2/ProcedureEvent.java