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

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Date:   Wed, 30 Nov 2016 15:40:51 +0200
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Yunjian Wang <wangyunjian@...wei.com>
Cc:     jasowang@...hat.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 08:10:57PM +0800, Yunjian Wang wrote:
> When we meet an error(err=-EBADFD) recvmsg,

How do you get EBADFD? Won't vhost_net_rx_peek_head_len
return 0 in this case, breaking the loop?

> 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;

You might get e.g. EAGAIN and I think you need to retry
in this case.

>  			continue;
>  		}
>  		/* Supply virtio_net_hdr if VHOST_NET_F_VIRTIO_NET_HDR */
> -- 
> 1.9.5.msysgit.1
>