diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
index 20d6d3f..6663a63 100644
--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c
@@ -344,6 +344,13 @@ static int smcr_lgr_reg_rmbs(struct smc_link *link,
 	struct smc_link_group *lgr = link->lgr;
 	int i, rc = 0;
 
+	rc = smc_llc_flow_initiate(lgr, SMC_LLC_FLOW_RKEY);
+	if (rc)
+		return rc;
+	/* protect against parallel smc_llc_cli_rkey_exchange() and
+	 * parallel smcr_link_reg_rmb()
+	 */
+	mutex_lock(&lgr->llc_conf_mutex);
 	for (i = 0; i < SMC_LINKS_PER_LGR_MAX; i++) {
 		if (lgr->lnk[i].state != SMC_LNK_ACTIVE)
 			continue;
@@ -360,6 +367,8 @@ static int smcr_lgr_reg_rmbs(struct smc_link *link,
 	}
 	rmb_desc->is_conf_rkey = true;
 out:
+	mutex_unlock(&lgr->llc_conf_mutex);
+	smc_llc_flow_stop(lgr, &lgr->llc_flow_lcl);
 	return rc;
 }
 
diff --git a/net/smc/smc_core.c b/net/smc/smc_core.c
index c905675..4c3af05 100644
--- a/net/smc/smc_core.c
+++ b/net/smc/smc_core.c
@@ -448,11 +448,21 @@ static int smc_lgr_create(struct smc_sock *smc, struct smc_init_info *ini)
 static void smcr_buf_unuse(struct smc_buf_desc *rmb_desc,
 			   struct smc_link_group *lgr)
 {
+	int rc;
+
 	if (rmb_desc->is_conf_rkey && !list_empty(&lgr->list)) {
 		/* unregister rmb with peer */
-		smc_llc_do_delete_rkey(lgr, rmb_desc);
-		rmb_desc->is_conf_rkey = false;
+		rc = smc_llc_flow_initiate(lgr, SMC_LLC_FLOW_RKEY);
+		if (!rc) {
+			/* protect against smc_llc_cli_rkey_exchange() */
+			mutex_lock(&lgr->llc_conf_mutex);
+			smc_llc_do_delete_rkey(lgr, rmb_desc);
+			rmb_desc->is_conf_rkey = false;
+			mutex_unlock(&lgr->llc_conf_mutex);
+			smc_llc_flow_stop(lgr, &lgr->llc_flow_lcl);
+		}
 	}
+
 	if (rmb_desc->is_reg_err) {
 		/* buf registration failed, reuse not possible */
 		mutex_lock(&lgr->rmbs_lock);
@@ -552,6 +562,7 @@ static void smcr_rtoken_clear_link(struct smc_link *lnk)
 	}
 }
 
+/* must be called under lgr->llc_conf_mutex lock */
 void smcr_link_clear(struct smc_link *lnk)
 {
 	struct smc_ib_device *smcibdev;
@@ -1170,7 +1181,9 @@ static int smcr_buf_map_link(struct smc_buf_desc *buf_desc, bool is_rmb,
 	return rc;
 }
 
-/* register a new rmb on IB device */
+/* register a new rmb on IB device,
+ * must be called under lgr->llc_conf_mutex lock
+ */
 int smcr_link_reg_rmb(struct smc_link *link, struct smc_buf_desc *rmb_desc)
 {
 	if (list_empty(&link->lgr->list))
@@ -1224,7 +1237,9 @@ int smcr_buf_map_lgr(struct smc_link *lnk)
 	return 0;
 }
 
-/* register all used buffers of lgr for a new link */
+/* register all used buffers of lgr for a new link,
+ * must be called under lgr->llc_conf_mutex lock
+ */
 int smcr_buf_reg_lgr(struct smc_link *lnk)
 {
 	struct smc_link_group *lgr = lnk->lgr;
@@ -1278,6 +1293,8 @@ static int smcr_buf_map_usable_links(struct smc_link_group *lgr,
 {
 	int i, rc = 0;
 
+	/* protect against parallel link reconfiguration */
+	mutex_lock(&lgr->llc_conf_mutex);
 	for (i = 0; i < SMC_LINKS_PER_LGR_MAX; i++) {
 		struct smc_link *lnk = &lgr->lnk[i];
 
@@ -1289,6 +1306,7 @@ static int smcr_buf_map_usable_links(struct smc_link_group *lgr,
 		}
 	}
 out:
+	mutex_unlock(&lgr->llc_conf_mutex);
 	return rc;
 }
 
diff --git a/net/smc/smc_core.h b/net/smc/smc_core.h
index 61ddb52..aa198dd 100644
--- a/net/smc/smc_core.h
+++ b/net/smc/smc_core.h
@@ -248,6 +248,8 @@ struct smc_link_group {
 						/* queue for llc events */
 			spinlock_t		llc_event_q_lock;
 						/* protects llc_event_q */
+			struct mutex		llc_conf_mutex;
+						/* protects lgr reconfig. */
 			struct work_struct	llc_event_work;
 						/* llc event worker */
 			wait_queue_head_t	llc_waiter;
diff --git a/net/smc/smc_llc.c b/net/smc/smc_llc.c
index 1718359..ceed3c8 100644
--- a/net/smc/smc_llc.c
+++ b/net/smc/smc_llc.c
@@ -848,6 +848,7 @@ void smc_llc_lgr_init(struct smc_link_group *lgr, struct smc_sock *smc)
 	spin_lock_init(&lgr->llc_event_q_lock);
 	spin_lock_init(&lgr->llc_flow_lock);
 	init_waitqueue_head(&lgr->llc_waiter);
+	mutex_init(&lgr->llc_conf_mutex);
 	lgr->llc_testlink_time = net->ipv4.sysctl_tcp_keepalive_time;
 }
 
@@ -897,9 +898,6 @@ int smc_llc_do_confirm_rkey(struct smc_link *send_link,
 	struct smc_llc_qentry *qentry = NULL;
 	int rc = 0;
 
-	rc = smc_llc_flow_initiate(lgr, SMC_LLC_FLOW_RKEY);
-	if (rc)
-		return rc;
 	rc = smc_llc_send_confirm_rkey(send_link, rmb_desc);
 	if (rc)
 		goto out;
@@ -911,7 +909,6 @@ int smc_llc_do_confirm_rkey(struct smc_link *send_link,
 out:
 	if (qentry)
 		smc_llc_flow_qentry_del(&lgr->llc_flow_lcl);
-	smc_llc_flow_stop(lgr, &lgr->llc_flow_lcl);
 	return rc;
 }
 
@@ -927,9 +924,6 @@ int smc_llc_do_delete_rkey(struct smc_link_group *lgr,
 	if (!send_link)
 		return -ENOLINK;
 
-	rc = smc_llc_flow_initiate(lgr, SMC_LLC_FLOW_RKEY);
-	if (rc)
-		return rc;
 	/* protected by llc_flow control */
 	rc = smc_llc_send_delete_rkey(send_link, rmb_desc);
 	if (rc)
@@ -942,7 +936,6 @@ int smc_llc_do_delete_rkey(struct smc_link_group *lgr,
 out:
 	if (qentry)
 		smc_llc_flow_qentry_del(&lgr->llc_flow_lcl);
-	smc_llc_flow_stop(lgr, &lgr->llc_flow_lcl);
 	return rc;
 }