protected void wakePollIfNeeded(final int waitingCount) {
    if (waitingCount <= 0) {
      return;
    }
    if (waitingCount == 1) {
      schedWaitCond.signal();
    } else {
      schedWaitCond.signalAll();
    }
  }
Wakes up given waiting procedures by pushing them back into scheduler queues.
@return size of given {@code waitQueue}.
hbase-procedure/src/main/java/org/apache/hadoop/hbase/procedure2/AbstractProcedureScheduler.java