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Message-ID: <20141113223241.GA4867@hercules>
Date: Thu, 13 Nov 2014 22:32:41 +0000
From: Luis Henriques <luis.henriques@...onical.com>
To: Eric Dumazet <eric.dumazet@...il.com>
Cc: David Miller <davem@...emloft.net>,
netdev <netdev@...r.kernel.org>,
Neal Cardwell <ncardwell@...gle.com>,
Joseph Salisbury <joseph.salisbury@...onical.com>
Subject: Re: [PATCH] net: skb_fclone_busy() needs to detect orphaned skb
On Thu, Nov 13, 2014 at 01:20:22PM -0800, Eric Dumazet wrote:
> On Thu, 2014-11-13 at 19:15 +0000, Luis Henriques wrote:
> > Hi Eric,
> >
> > On Thu, Oct 30, 2014 at 10:32:34AM -0700, Eric Dumazet wrote:
> > > From: Eric Dumazet <edumazet@...gle.com>
> > >
> > > Some drivers are unable to perform TX completions in a bound time.
> > > They instead call skb_orphan()
> > >
> > > Problem is skb_fclone_busy() has to detect this case, otherwise
> > > we block TCP retransmits and can freeze unlucky tcp sessions on
> > > mostly idle hosts.
> > >
> > > Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> > > Fixes: 1f3279ae0c13 ("tcp: avoid retransmits of TCP packets hanging in host queues")
> > > ---
> > > This is a stable candidate.
> > > This problem is known to hurt users of linux-3.16 kernels used by guests kernels.
> > > David, I can provide backports if you want.
> > > Thanks !
> > >
> >
> > We got a bug report[0] where a backport for 3.16 was provided. Since
> > I couldn't find the original backport post, I'm not sure who's the
> > actual author. Could you please confirm if this backport is correct?
> > (I'm copying the patch below).
> >
> > [0] https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1390604
> >
> > Cheers,
> > --
> > Luís
> >
> >
>
> Sure ! I provided this patch indeed, I am 'The Google engineer'
> mentioned in this bug report ;)
>
Awesome, Thanks! I'll queue it for the 3.16 kernel. Since I couldn't
find the original patch, I could only guess who 'The Google engineer'
was :-)
Cheers,
--
Luís
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
>
>
> Thanks !
>
> > diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
> > index 4e4932b5079b..a8794367cd20 100644
> > --- a/net/ipv4/tcp_output.c
> > +++ b/net/ipv4/tcp_output.c
> > @@ -2082,7 +2082,8 @@ static bool skb_still_in_host_queue(const struct sock *sk,
> > const struct sk_buff *fclone = skb + 1;
> >
> > if (unlikely(skb->fclone == SKB_FCLONE_ORIG &&
> > - fclone->fclone == SKB_FCLONE_CLONE)) {
> > + fclone->fclone == SKB_FCLONE_CLONE &&
> > + fclone->sk == sk)) {
> > NET_INC_STATS_BH(sock_net(sk),
> > LINUX_MIB_TCPSPURIOUS_RTX_HOSTQUEUES);
> > return true;
>
>
>
>
--
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