netdev - RE: [PATCHv1 net] xen-netback: fix guest Rx stall detection (after guest Rx refactor)

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Date:   Tue, 11 Oct 2016 15:54:38 +0000
From:   Paul Durrant <Paul.Durrant@...rix.com>
To:     David Vrabel <david.vrabel@...rix.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
CC:     David Vrabel <david.vrabel@...rix.com>,
        "xen-devel@...ts.xenproject.org" <xen-devel@...ts.xenproject.org>,
        Wei Liu <wei.liu2@...rix.com>
Subject: RE: [PATCHv1 net] xen-netback: fix guest Rx stall detection (after
 guest Rx refactor)

> -----Original Message-----
> From: David Vrabel [mailto:david.vrabel@...rix.com]
> Sent: 11 October 2016 16:48
> To: netdev@...r.kernel.org
> Cc: David Vrabel <david.vrabel@...rix.com>; xen-devel@...ts.xenproject.org;
> Paul Durrant <Paul.Durrant@...rix.com>; Wei Liu <wei.liu2@...rix.com>
> Subject: [PATCHv1 net] xen-netback: fix guest Rx stall detection (after guest
> Rx refactor)
> 
> If a VIF has been ready for rx_stall_timeout (60s by default) and an
> Rx ring is drained of all requests an Rx stall will be incorrectly
> detected.  When this occurs and the guest Rx queue is empty, the Rx
> ring's event index will not be set and the frontend will not raise an
> event when new requests are placed on the ring, permanently stalling
> the VIF.
> 
> This is a regression introduced by eb1723a29b9a7 (xen-netback:
> refactor guest rx).
> 
> Fix this by reinstating the setting of queue->last_rx_time when
> placing a packet onto the guest Rx ring.
> 
> Signed-off-by: David Vrabel <david.vrabel@...rix.com>
Reviewed-by: Paul Durrant <paul.durrant@...rix.com>

> ---
>  drivers/net/xen-netback/rx.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/net/xen-netback/rx.c b/drivers/net/xen-netback/rx.c
> index 8e9ade6..d69f2a9 100644
> --- a/drivers/net/xen-netback/rx.c
> +++ b/drivers/net/xen-netback/rx.c
> @@ -425,6 +425,8 @@ void xenvif_rx_skb(struct xenvif_queue *queue)
> 
>  	xenvif_rx_next_skb(queue, &pkt);
> 
> +	queue->last_rx_time = jiffies;
> +
>  	do {
>  		struct xen_netif_rx_request *req;
>  		struct xen_netif_rx_response *rsp;
> --
> 2.1.4