code: void initializeReplQueues() throws SafeModeException {
      writeLock();
      try {
        if (isPopulatingReplQueues()) {
          NameNode.stateChangeLog.info("STATE* Safe mode is already OFF."
              + " Replication queues are initialized");
          return;
        }
        safeMode.initializeReplicationQueues();
      } finally {
        writeUnlock();
      }
    }
docs: Manually initialize replication queues when in safemode.