From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [PATCH net-next] tun: don't require serialization lock on tx Date: Sun, 17 Apr 2016 13:20:45 +0300 Message-ID: <20160417132004-mutt-send-email-mst@redhat.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: netdev@vger.kernel.org, "David S. Miller" , Hannes Frederic Sowa , "Eric W. Biederman" , Greg Kurz , Jason Wang , Eric Dumazet To: Paolo Abeni Return-path: Received: from mx1.redhat.com ([209.132.183.28]:50762 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751590AbcDQKUu (ORCPT ); Sun, 17 Apr 2016 06:20:50 -0400 Content-Disposition: inline In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: On Thu, Apr 14, 2016 at 06:39:39PM +0200, Paolo Abeni wrote: > The current tun_net_xmit() implementation don't need any external > lock since it relies 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. > > The user space can remove the default tun qdisc with: > > tc qdisc replace dev root noqueue > > Signed-off-by: Paolo Abeni > Acked-by: Hannes Frederic Sowa > Acked-by: Eric Dumazet This one seems transparent to userspace so: Acked-by: Michael S. Tsirkin > > --- > RFC -> v1 > - fixed a commit message typo, extended the comment with a > configuration hint > --- > 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; > dev->vlan_features = dev->features & > ~(NETIF_F_HW_VLAN_CTAG_TX | > NETIF_F_HW_VLAN_STAG_TX); > -- > 1.8.3.1