@Override
  public boolean offer(T t) {
    lock.lock();
    try {
      notEmpty.signal();
      return super.offer(t);
    } finally {
      lock.unlock();
    }
  }
Get a queue whose job might be stolen by the consumer of this original queue
@return the queue whose job could be stolen
hbase-server/src/main/java/org/apache/hadoop/hbase/util/StealJobQueue.java