macvlan: schedule bc_work even if error

While enqueueing a broadcast skb to port->bc_queue, schedule_work()
is called to add port->bc_work, which processes the skbs in
bc_queue, to "events" work queue. If port->bc_queue is full, the
skb will be discarded and schedule_work(&port->bc_work) won't be
called. However, if port->bc_queue is full and port->bc_work is not
running or pending, port->bc_queue will keep full and schedule_work()
won't be called any more, and all broadcast skbs to macvlan will be
discarded. This case can happen:

macvlan_process_broadcast() is the pending function of port->bc_work,
it moves all the skbs in port->bc_queue to the queue "list", and
processes the skbs in "list". During this, new skbs will keep being
added to port->bc_queue in macvlan_broadcast_enqueue(), and
port->bc_queue may already full when macvlan_process_broadcast()
return. This may happen, especially when there are a lot of real-time
threads and the process is preempted.

Fix this by calling schedule_work(&port->bc_work) even if
port->bc_work is full in macvlan_broadcast_enqueue().

Fixes: 412ca155 ("macvlan: Move broadcasts into a work queue")
Signed-off-by: Menglong Dong <dong.menglong@zte.com.cn>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/macvlan.c

@@ -359,10 +359,11 @@ static void macvlan_broadcast_enqueue(struct macvlan_port *port,
 	}
 	spin_unlock(&port->bc_queue.lock);
 
+	schedule_work(&port->bc_work);
+
 	if (err)
 		goto free_nskb;
 
-	schedule_work(&port->bc_work);
 	return;
 
 free_nskb: