[PATCH net-next v2 03/10] tun: switch to net core provided statistics counters

[Jakub Kicinski]

On Wed, 4 Nov 2020 15:25:24 +0100 Heiner Kallweit wrote:
> @@ -1066,7 +1054,7 @@ static netdev_tx_t tun_net_xmit(struct sk_buff *skb, struct net_device *dev)
>  	return NETDEV_TX_OK;
>  
>  drop:
> -	this_cpu_inc(tun->pcpu_stats->tx_dropped);
> +	dev->stats.tx_dropped++;
>  	skb_tx_error(skb);
>  	kfree_skb(skb);
>  	rcu_read_unlock();

This is no longer atomic. Multiple CPUs may try to update it at the
same time.

Do you know what the story on dev->rx_dropped is? The kdoc says drivers
are not supposed to use it but:

drivers/net/ipvlan/ipvlan_core.c:               atomic_long_inc(&skb->dev->rx_dropped);
drivers/net/macvlan.c:  atomic_long_inc(&skb->dev->rx_dropped);
drivers/net/vxlan.c:            atomic_long_inc(&vxlan->dev->rx_dropped);

Maybe tun can use it, too?