netdev - Re: [PATCH v2 net] wireguard: use DEV_STATS

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Date: Mon, 20 Nov 2023 08:56:02 +0100
From: Eric Dumazet <edumazet@...gle.com>
To: "Jason A. Donenfeld" <Jason@...c4.com>
Cc: patchwork-bot+netdevbpf@...nel.org, davem@...emloft.net, kuba@...nel.org, 
	pabeni@...hat.com, netdev@...r.kernel.org, eric.dumazet@...il.com, 
	syzkaller@...glegroups.com, liuhangbin@...il.com
Subject: Re: [PATCH v2 net] wireguard: use DEV_STATS_INC()

On Mon, Nov 20, 2023 at 1:11 AM Jason A. Donenfeld <Jason@...c4.com> wrote:
>
> Hi,
>
> On Sun, Nov 19, 2023 at 8:50 PM <patchwork-bot+netdevbpf@...nel.org> wrote:
> >
> > Hello:
> >
> > This patch was applied to netdev/net.git (main)
> > by David S. Miller <davem@...emloft.net>:
> >
> > On Fri, 17 Nov 2023 14:17:33 +0000 you wrote:
> > > wg_xmit() can be called concurrently, KCSAN reported [1]
> > > some device stats updates can be lost.
> > >
> > > Use DEV_STATS_INC() for this unlikely case.
> > >
> > > [1]
> > > BUG: KCSAN: data-race in wg_xmit / wg_xmit
> > >
> > > [...]
> >
> > Here is the summary with links:
> >   - [v2,net] wireguard: use DEV_STATS_INC()
> >     https://git.kernel.org/netdev/net/c/93da8d75a665
> >
> > You are awesome, thank you!
>
> I thought that, given my concerns, if this was to be committed, at
> least Eric (or you?) would expand on the rationale in the context of
> my concerns while (or before) doing so, rather than just applying this
> without further discussion. As I mentioned, this is fine with me if
> you feel strongly about it, but I would appreciate some expanded
> explanation, just for my own understanding of the matter.
>
> Jason

Jason, I was in week end mode, so could not reply to your message.

This fix is rather obvious to me. I do not want to spend too much time on it,
and you gave an ACK if I am not mistaken.

If you prefer not letting syzbot find other bugs in wireguard (because
hitting this issue first),
this is fine by me. We can ask syzbot team to not include wireguard in
their kernels.