code: public void stopLeaseMonitor() throws InterruptedException {
      if (lmmonitor != null) {
        lmmonitor.stop();
        InjectionHandler
            .processEvent(InjectionEvent.FSNAMESYSTEM_STOP_LEASEMANAGER);
      }
      if (lmthread != null) {
        // interrupt the lease monitor thread. We need to make sure the
        // interruption does not happen during
        // LeaseManager.checkLeases(), which would possibly interfere with writing
        // to edit log, and hence with clean shutdown. It essential during
        // failover, as it could exclude edit log streams!!!
        writeLock();
        try {
          lmthread.interrupt();
        } finally {
          writeUnlock();
        }
        lmthread.join();
      }
    }
docs: Stops lease monitor thread.