linux-kernel - Re: [PATCH net] vhost_net: don't continue to call the recvmsg when meet errors

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Message-ID: <20161130154250-mutt-send-email-mst@kernel.org>
Date:   Wed, 30 Nov 2016 15:43:48 +0200
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Jason Wang <jasowang@...hat.com>
Cc:     Yunjian Wang <wangyunjian@...wei.com>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, caihe@...wei.com
Subject: Re: [PATCH net] vhost_net: don't continue to call the recvmsg when
 meet errors

On Wed, Nov 30, 2016 at 09:07:16PM +0800, Jason Wang wrote:
> 
> 
> On 2016年11月30日 20:10, Yunjian Wang wrote:
> > When we meet an error(err=-EBADFD) recvmsg, the error handling in vhost
> > handle_rx() will continue. This will cause a soft CPU lockup in vhost thread.
> > 
> > Signed-off-by: Yunjian Wang <wangyunjian@...wei.com>
> > ---
> >   drivers/vhost/net.c | 3 +++
> >   1 file changed, 3 insertions(+)
> > 
> > diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
> > index 5dc128a..edc470b 100644
> > --- a/drivers/vhost/net.c
> > +++ b/drivers/vhost/net.c
> > @@ -717,6 +717,9 @@ static void handle_rx(struct vhost_net *net)
> >   			pr_debug("Discarded rx packet: "
> >   				 " len %d, expected %zd\n", err, sock_len);
> >   			vhost_discard_vq_desc(vq, headcount);
> > +			/* Don't continue to do, when meet errors. */
> > +			if (err < 0)
> > +				goto out;
> >   			continue;
> >   		}
> >   		/* Supply virtio_net_hdr if VHOST_NET_F_VIRTIO_NET_HDR */
> 
> Acked-by: Jason Wang <jasowang@...hat.com>
> 
> We may want to rename vhost_discard_vq_desc() in the future, since it does
> not discard the desc in fact.

To me this looks a bit too aggressive. I would also like commit log
to explain better what is going on, to make sure we are
not just treating the symptoms.
-- 
MST