@@ -58,6 +58,7 @@
 #include <linux/can/skb.h>
 #include <linux/can/bcm.h>
 #include <linux/slab.h>
+#include <linux/spinlock.h>
 #include <net/sock.h>
 #include <net/net_namespace.h>
 

@@ -120,6 +121,7 @@ struct bcm_op {
 	struct canfd_frame last_sframe;
 	struct sock *sk;
 	struct net_device *rx_reg_dev;
+	spinlock_t bcm_tx_lock; /* protect currframe/count in runtime updates */
 };
 
 struct bcm_sock {

@@ -273,13 +275,18 @@ static void bcm_can_tx(struct bcm_op *op
 {
 	struct sk_buff *skb;
 	struct net_device *dev;
-	struct canfd_frame *cf = op->frames + op->cfsiz * op->currframe;
+	struct canfd_frame *cf;
 	int err;
 
 	/* no target device? => exit */
 	if (!op->ifindex)
 		return;
 
+	/* read currframe under lock protection */
+	spin_lock_bh(&op->bcm_tx_lock);
+	cf = op->frames + op->cfsiz * op->currframe;
+	spin_unlock_bh(&op->bcm_tx_lock);
+
 	dev = dev_get_by_index(sock_net(op->sk), op->ifindex);
 	if (!dev) {
 		/* RFC: should this bcm_op remove itself here? */

@@ -300,6 +307,10 @@ static void bcm_can_tx(struct bcm_op *op
 	skb->dev = dev;
 	can_skb_set_owner(skb, op->sk);
 	err = can_send(skb, 1);
+
+	/* update currframe and count under lock protection */
+	spin_lock_bh(&op->bcm_tx_lock);
+
 	if (!err)
 		op->frames_abs++;
 

@@ -308,6 +319,11 @@ static void bcm_can_tx(struct bcm_op *op
 	/* reached last frame? */
 	if (op->currframe >= op->nframes)
 		op->currframe = 0;
+
+	if (op->count > 0)
+		op->count--;
+
+	spin_unlock_bh(&op->bcm_tx_lock);
 out:
 	dev_put(dev);
 }

@@ -404,7 +420,7 @@ static enum hrtimer_restart bcm_tx_timeo
 	struct bcm_msg_head msg_head;
 
 	if (op->kt_ival1 && (op->count > 0)) {
-		op->count--;
+		bcm_can_tx(op);
 		if (!op->count && (op->flags & TX_COUNTEVT)) {
 
 			/* create notification to user */

@@ -419,7 +435,6 @@ static enum hrtimer_restart bcm_tx_timeo
 
 			bcm_send_to_user(op, &msg_head, NULL, 0);
 		}
-		bcm_can_tx(op);
 
 	} else if (op->kt_ival2) {
 		bcm_can_tx(op);

@@ -914,6 +929,27 @@ static int bcm_tx_setup(struct bcm_msg_h
 		}
 		op->flags = msg_head->flags;
 
+		/* only lock for unlikely count/nframes/currframe changes */
+		if (op->nframes != msg_head->nframes ||
+		    op->flags & TX_RESET_MULTI_IDX ||
+		    op->flags & SETTIMER) {
+
+			spin_lock_bh(&op->bcm_tx_lock);
+
+			if (op->nframes != msg_head->nframes ||
+			    op->flags & TX_RESET_MULTI_IDX) {
+				/* potentially update changed nframes */
+				op->nframes = msg_head->nframes;
+				/* restart multiple frame transmission */
+				op->currframe = 0;
+			}
+
+			if (op->flags & SETTIMER)
+				op->count = msg_head->count;
+
+			spin_unlock_bh(&op->bcm_tx_lock);
+		}
+
 	} else {
 		/* insert new BCM operation for the given can_id */
 

@@ -921,9 +957,14 @@ static int bcm_tx_setup(struct bcm_msg_h
 		if (!op)
 			return -ENOMEM;
 
+		spin_lock_init(&op->bcm_tx_lock);
 		op->can_id = msg_head->can_id;
 		op->cfsiz = CFSIZ(msg_head->flags);
 		op->flags = msg_head->flags;
+		op->nframes = msg_head->nframes;
+
+		if (op->flags & SETTIMER)
+			op->count = msg_head->count;
 
 		/* create array for CAN frames and copy the data */
 		if (msg_head->nframes > 1) {

@@ -982,22 +1023,8 @@ static int bcm_tx_setup(struct bcm_msg_h
 
 	} /* if ((op = bcm_find_op(&bo->tx_ops, msg_head->can_id, ifindex))) */
 
-	if (op->nframes != msg_head->nframes) {
-		op->nframes   = msg_head->nframes;
-		/* start multiple frame transmission with index 0 */
-		op->currframe = 0;
-	}
-
-	/* check flags */
-
-	if (op->flags & TX_RESET_MULTI_IDX) {
-		/* start multiple frame transmission with index 0 */
-		op->currframe = 0;
-	}
-
 	if (op->flags & SETTIMER) {
 		/* set timer values */
-		op->count = msg_head->count;
 		op->ival1 = msg_head->ival1;
 		op->ival2 = msg_head->ival2;
 		op->kt_ival1 = bcm_timeval_to_ktime(msg_head->ival1);

@@ -1014,11 +1041,8 @@ static int bcm_tx_setup(struct bcm_msg_h
 		op->flags |= TX_ANNOUNCE;
 	}
 
-	if (op->flags & TX_ANNOUNCE) {
+	if (op->flags & TX_ANNOUNCE)
 		bcm_can_tx(op);
-		if (op->count)
-			op->count--;
-	}
 
 	if (op->flags & STARTTIMER)
 		bcm_tx_start_timer(op);