radosgw-admin metadata sync run

Hi folks, What is the purpose of this command? It is always stuck and its debug log shows that it couldn't get locks on mdlog.sync-status* objects, which are constantly locked by the running radosgw process (every 60 seconds, it will ensure it gets the lock). It appears that RGWMetaSyncShardCR::incremental_sync() never gets out of the do-while loop until can_adjust_marker is false, which is only set as such when one of its children returns an error. So, it seems that during normal operation, this loop never ends. Thus, it always holds sync status object locks, thus renders this command useless. Or did I use it wrong? Thanks, Yixin