On Wed, Apr 13, 2016 at 11:04:46AM +0200, Paolo Abeni wrote:
> The current tun_net_xmit() implementation don't need any external
> lock since it relay on rcu protection for the tun data structure
> and on socket queue lock for skb queuing.
>
> This patch set the NETIF_F_LLTX feature bit in the tun device, so
> that on xmit, in absence of qdisc, no serialization lock is acquired
> by the caller.
>
> Signed-off-by: Paolo Abeni <[email protected]>
> ---
> drivers/net/tun.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> index faf9297..42992dc 100644
> --- a/drivers/net/tun.c
> +++ b/drivers/net/tun.c
> @@ -1796,7 +1796,7 @@ static int tun_set_iff(struct net *net, struct file
> *file, struct ifreq *ifr)
> dev->hw_features = NETIF_F_SG | NETIF_F_FRAGLIST |
> TUN_USER_FEATURES | NETIF_F_HW_VLAN_CTAG_TX |
> NETIF_F_HW_VLAN_STAG_TX;
> - dev->features = dev->hw_features;
> + dev->features = dev->hw_features | NETIF_F_LLTX;
the documentation says:
NETIF_F_LLTX_BIT, /* LockLess TX - deprecated. Please */
/* do not use LLTX in new drivers */
git log gives this explanation:
> 1) unnecessary;
> 2) causes problems with AF_PACKET seeing things twice.
> dev->vlan_features = dev->features &
> ~(NETIF_F_HW_VLAN_CTAG_TX |
> NETIF_F_HW_VLAN_STAG_TX);
> --
> 1.8.3.1
