[DLM] schedule during long loop through locks

The loop through all waiting locks in recover_waiters can potentially be
long, so we should schedule explicitly.
Signed-off-by: David Teigland <teigland@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

fs/dlm/lock.c

@@ -3193,6 +3193,7 @@ void dlm_recover_waiters_pre(struct dlm_ls *ls)
 			log_error(ls, "invalid lkb wait_type %d",
 				  lkb->lkb_wait_type);
 		}
+		schedule();
 	}
 	mutex_unlock(&ls->ls_waiters_mutex);
 }