linux-kernel - Re: [PATCH v2] ip_tunnel: disable preemption when updating per-cpu tstats

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Date:	Mon, 16 Nov 2015 20:33:42 +0100
From:	"Jason A. Donenfeld" <Jason@...c4.com>
To:	David Miller <davem@...emloft.net>
Cc:	Netdev <netdev@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>, tgraf@...g.ch,
	Tom Herbert <tom@...bertland.com>,
	Jiri Benc <jbenc@...hat.com>,
	Alexey Kuznetsov <kuznet@....inr.ac.ru>
Subject: Re: [PATCH v2] ip_tunnel: disable preemption when updating per-cpu tstats

On Mon, Nov 16, 2015 at 8:17 PM, David Miller <davem@...emloft.net> wrote:
> So another fix could have been to do local_bh_disable() in the
> udp_tunnel6_xmit_skb() helper.

This would have fixed one problem, but everywhere
udp_tunnel_xmit_skb() (4, not 6) is called, iptunnel_xmit_stats is
called right after it, so there would have to be a modicum of patches
for all of these places too.

By the way, there's something else I noticed about this in dealing
with these functions: the return value of udp_tunnel_xmit_skb is
different from that of udp_tunnel6_xmit_skb. Nobody is using them
incorrectly, so far as I can see, but it is confusing that they return
different things. I had started to clean this up and send a patch, but
it got a bit invasive in drivers I shouldn't really touch. But if
somebody with a bit more top-down command of things wants to poke at
this, it's a low hanging fruit as far as I can see.

>
> Thanks again.

My pleasure.
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