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

[Heiner Kallweit]

On 06.11.2020 02:14, Jakub Kicinski wrote:
> 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?
> 
Thanks, yes that should be possible. Here we speak about tx_dropped,
but AFAICS the same applies as for rx_dropped. Will change it accordingly
in a v3.