diff --git a/fs/dlm/config.c b/fs/dlm/config.c
index 0d329ff..9b026ea 100644
--- a/fs/dlm/config.c
+++ b/fs/dlm/config.c
@@ -100,6 +100,7 @@
 	unsigned int cl_log_debug;
 	unsigned int cl_protocol;
 	unsigned int cl_timewarn_cs;
+	unsigned int cl_waitwarn_us;
 };
 
 enum {
@@ -114,6 +115,7 @@
 	CLUSTER_ATTR_LOG_DEBUG,
 	CLUSTER_ATTR_PROTOCOL,
 	CLUSTER_ATTR_TIMEWARN_CS,
+	CLUSTER_ATTR_WAITWARN_US,
 };
 
 struct cluster_attribute {
@@ -166,6 +168,7 @@
 CLUSTER_ATTR(log_debug, 0);
 CLUSTER_ATTR(protocol, 0);
 CLUSTER_ATTR(timewarn_cs, 1);
+CLUSTER_ATTR(waitwarn_us, 0);
 
 static struct configfs_attribute *cluster_attrs[] = {
 	[CLUSTER_ATTR_TCP_PORT] = &cluster_attr_tcp_port.attr,
@@ -179,6 +182,7 @@
 	[CLUSTER_ATTR_LOG_DEBUG] = &cluster_attr_log_debug.attr,
 	[CLUSTER_ATTR_PROTOCOL] = &cluster_attr_protocol.attr,
 	[CLUSTER_ATTR_TIMEWARN_CS] = &cluster_attr_timewarn_cs.attr,
+	[CLUSTER_ATTR_WAITWARN_US] = &cluster_attr_waitwarn_us.attr,
 	NULL,
 };
 
@@ -439,6 +443,7 @@
 	cl->cl_log_debug = dlm_config.ci_log_debug;
 	cl->cl_protocol = dlm_config.ci_protocol;
 	cl->cl_timewarn_cs = dlm_config.ci_timewarn_cs;
+	cl->cl_waitwarn_us = dlm_config.ci_waitwarn_us;
 
 	space_list = &sps->ss_group;
 	comm_list = &cms->cs_group;
@@ -986,6 +991,7 @@
 #define DEFAULT_LOG_DEBUG          0
 #define DEFAULT_PROTOCOL           0
 #define DEFAULT_TIMEWARN_CS      500 /* 5 sec = 500 centiseconds */
+#define DEFAULT_WAITWARN_US	   0
 
 struct dlm_config_info dlm_config = {
 	.ci_tcp_port = DEFAULT_TCP_PORT,
@@ -998,6 +1004,7 @@
 	.ci_scan_secs = DEFAULT_SCAN_SECS,
 	.ci_log_debug = DEFAULT_LOG_DEBUG,
 	.ci_protocol = DEFAULT_PROTOCOL,
-	.ci_timewarn_cs = DEFAULT_TIMEWARN_CS
+	.ci_timewarn_cs = DEFAULT_TIMEWARN_CS,
+	.ci_waitwarn_us = DEFAULT_WAITWARN_US
 };
 
diff --git a/fs/dlm/config.h b/fs/dlm/config.h
index 4f1d6fc..dd0ce24 100644
--- a/fs/dlm/config.h
+++ b/fs/dlm/config.h
@@ -28,6 +28,7 @@
 	int ci_log_debug;
 	int ci_protocol;
 	int ci_timewarn_cs;
+	int ci_waitwarn_us;
 };
 
 extern struct dlm_config_info dlm_config;
diff --git a/fs/dlm/dlm_internal.h b/fs/dlm/dlm_internal.h
index b942049..6a92478 100644
--- a/fs/dlm/dlm_internal.h
+++ b/fs/dlm/dlm_internal.h
@@ -245,6 +245,7 @@
 
 	int8_t			lkb_wait_type;	/* type of reply waiting for */
 	int8_t			lkb_wait_count;
+	int			lkb_wait_nodeid; /* for debugging */
 
 	struct list_head	lkb_idtbl_list;	/* lockspace lkbtbl */
 	struct list_head	lkb_statequeue;	/* rsb g/c/w list */
@@ -254,6 +255,7 @@
 	struct list_head	lkb_ownqueue;	/* list of locks for a process */
 	struct list_head	lkb_time_list;
 	ktime_t			lkb_timestamp;
+	ktime_t			lkb_wait_time;
 	unsigned long		lkb_timeout_cs;
 
 	struct dlm_callback	lkb_callbacks[DLM_CALLBACKS_SIZE];
diff --git a/fs/dlm/lock.c b/fs/dlm/lock.c
index 04b8c44..e3c8641 100644
--- a/fs/dlm/lock.c
+++ b/fs/dlm/lock.c
@@ -799,10 +799,84 @@
 	return -1;
 }
 
+static int nodeid_warned(int nodeid, int num_nodes, int *warned)
+{
+	int i;
+
+	for (i = 0; i < num_nodes; i++) {
+		if (!warned[i]) {
+			warned[i] = nodeid;
+			return 0;
+		}
+		if (warned[i] == nodeid)
+			return 1;
+	}
+	return 0;
+}
+
+void dlm_scan_waiters(struct dlm_ls *ls)
+{
+	struct dlm_lkb *lkb;
+	ktime_t zero = ktime_set(0, 0);
+	s64 us;
+	s64 debug_maxus = 0;
+	u32 debug_scanned = 0;
+	u32 debug_expired = 0;
+	int num_nodes = 0;
+	int *warned = NULL;
+
+	if (!dlm_config.ci_waitwarn_us)
+		return;
+
+	mutex_lock(&ls->ls_waiters_mutex);
+
+	list_for_each_entry(lkb, &ls->ls_waiters, lkb_wait_reply) {
+		if (ktime_equal(lkb->lkb_wait_time, zero))
+			continue;
+
+		debug_scanned++;
+
+		us = ktime_to_us(ktime_sub(ktime_get(), lkb->lkb_wait_time));
+
+		if (us < dlm_config.ci_waitwarn_us)
+			continue;
+
+		lkb->lkb_wait_time = zero;
+
+		debug_expired++;
+		if (us > debug_maxus)
+			debug_maxus = us;
+
+		if (!num_nodes) {
+			num_nodes = ls->ls_num_nodes;
+			warned = kmalloc(GFP_KERNEL, num_nodes * sizeof(int));
+			if (warned)
+				memset(warned, 0, num_nodes * sizeof(int));
+		}
+		if (!warned)
+			continue;
+		if (nodeid_warned(lkb->lkb_wait_nodeid, num_nodes, warned))
+			continue;
+
+		log_error(ls, "waitwarn %x %lld %d us check connection to "
+			  "node %d", lkb->lkb_id, (long long)us,
+			  dlm_config.ci_waitwarn_us, lkb->lkb_wait_nodeid);
+	}
+	mutex_unlock(&ls->ls_waiters_mutex);
+
+	if (warned)
+		kfree(warned);
+
+	if (debug_expired)
+		log_debug(ls, "scan_waiters %u warn %u over %d us max %lld us",
+			  debug_scanned, debug_expired,
+			  dlm_config.ci_waitwarn_us, (long long)debug_maxus);
+}
+
 /* add/remove lkb from global waiters list of lkb's waiting for
    a reply from a remote node */
 
-static int add_to_waiters(struct dlm_lkb *lkb, int mstype)
+static int add_to_waiters(struct dlm_lkb *lkb, int mstype, int to_nodeid)
 {
 	struct dlm_ls *ls = lkb->lkb_resource->res_ls;
 	int error = 0;
@@ -842,6 +916,8 @@
 
 	lkb->lkb_wait_count++;
 	lkb->lkb_wait_type = mstype;
+	lkb->lkb_wait_time = ktime_get();
+	lkb->lkb_wait_nodeid = to_nodeid; /* for debugging */
 	hold_lkb(lkb);
 	list_add(&lkb->lkb_wait_reply, &ls->ls_waiters);
  out:
@@ -1157,6 +1233,16 @@
 	list_for_each_entry(lkb, &ls->ls_timeout, lkb_time_list)
 		lkb->lkb_timestamp = ktime_add_us(lkb->lkb_timestamp, adj_us);
 	mutex_unlock(&ls->ls_timeout_mutex);
+
+	if (!dlm_config.ci_waitwarn_us)
+		return;
+
+	mutex_lock(&ls->ls_waiters_mutex);
+	list_for_each_entry(lkb, &ls->ls_waiters, lkb_wait_reply) {
+		if (ktime_to_us(lkb->lkb_wait_time))
+			lkb->lkb_wait_time = ktime_get();
+	}
+	mutex_unlock(&ls->ls_waiters_mutex);
 }
 
 /* lkb is master or local copy */
@@ -2844,12 +2930,12 @@
 	struct dlm_mhandle *mh;
 	int to_nodeid, error;
 
-	error = add_to_waiters(lkb, mstype);
+	to_nodeid = r->res_nodeid;
+
+	error = add_to_waiters(lkb, mstype, to_nodeid);
 	if (error)
 		return error;
 
-	to_nodeid = r->res_nodeid;
-
 	error = create_message(r, lkb, to_nodeid, mstype, &ms, &mh);
 	if (error)
 		goto fail;
@@ -2951,12 +3037,12 @@
 	struct dlm_mhandle *mh;
 	int to_nodeid, error;
 
-	error = add_to_waiters(lkb, DLM_MSG_LOOKUP);
+	to_nodeid = dlm_dir_nodeid(r);
+
+	error = add_to_waiters(lkb, DLM_MSG_LOOKUP, to_nodeid);
 	if (error)
 		return error;
 
-	to_nodeid = dlm_dir_nodeid(r);
-
 	error = create_message(r, NULL, to_nodeid, DLM_MSG_LOOKUP, &ms, &mh);
 	if (error)
 		goto fail;
diff --git a/fs/dlm/lock.h b/fs/dlm/lock.h
index 88e93c8..265017a 100644
--- a/fs/dlm/lock.h
+++ b/fs/dlm/lock.h
@@ -24,6 +24,7 @@
 void dlm_scan_rsbs(struct dlm_ls *ls);
 int dlm_lock_recovery_try(struct dlm_ls *ls);
 void dlm_unlock_recovery(struct dlm_ls *ls);
+void dlm_scan_waiters(struct dlm_ls *ls);
 void dlm_scan_timeout(struct dlm_ls *ls);
 void dlm_adjust_timeouts(struct dlm_ls *ls);
 
diff --git a/fs/dlm/lockspace.c b/fs/dlm/lockspace.c
index f994a7d..14cbf40 100644
--- a/fs/dlm/lockspace.c
+++ b/fs/dlm/lockspace.c
@@ -243,7 +243,6 @@
 static int dlm_scand(void *data)
 {
 	struct dlm_ls *ls;
-	int timeout_jiffies = dlm_config.ci_scan_secs * HZ;
 
 	while (!kthread_should_stop()) {
 		ls = find_ls_to_scan();
@@ -252,13 +251,14 @@
 				ls->ls_scan_time = jiffies;
 				dlm_scan_rsbs(ls);
 				dlm_scan_timeout(ls);
+				dlm_scan_waiters(ls);
 				dlm_unlock_recovery(ls);
 			} else {
 				ls->ls_scan_time += HZ;
 			}
-		} else {
-			schedule_timeout_interruptible(timeout_jiffies);
+			continue;
 		}
+		schedule_timeout_interruptible(dlm_config.ci_scan_secs * HZ);
 	}
 	return 0;
 }