From: David Vrabel <david.vrabel@citrix•com>
To: Wei Liu <wei.liu2@citrix•com>, <xen-devel@lists•xen.org>,
<netdev@vger•kernel.org>
Cc: Paul Durrant <paul.durrant@citrix•com>, <jajcus@jajcus•net>
Subject: Re: [Xen-devel] [PATCH net V2] xen-netback: don't move event pointer in TX credit timeout callback
Date: Thu, 15 May 2014 14:40:58 +0100 [thread overview]
Message-ID: <5374C3EA.1080807@citrix.com> (raw)
In-Reply-To: <1400155158-13527-1-git-send-email-wei.liu2@citrix.com>
On 15/05/14 12:59, Wei Liu wrote:
> ... otherwise the frontend will try to send TX event all the time, even
> if no progress can be made. The pointer should only be advanced by the
> routine that actually processes the ring (that is, xenvif_poll).
No it does not. RING_FINAL_CHECK_FOR_REQUESTS() only advances the event
index if the ring is empty.
This will also result in xenvif_up() failing to properly enable the event.
I think Jacek's bug may be that netback fails to call napi_complete()
when credit is exceeded and there still outstanding requests on the
from-guest ring and thus napi repeatedly polls.
David
>
> Reported-by: Jacek Konieczny <jajcus@jajcus•net>
> Signed-off-by: Wei Liu <wei.liu2@citrix•com>
> Acked-by: Ian Campbell <ian.campbell@citrix•com>
> Cc: Paul Durrant <paul.durrant@citrix•com>
> ---
> drivers/net/xen-netback/netback.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
> index 7666540..8e2cbeb 100644
> --- a/drivers/net/xen-netback/netback.c
> +++ b/drivers/net/xen-netback/netback.c
> @@ -658,7 +658,7 @@ void xenvif_check_rx_xenvif(struct xenvif *vif)
> {
> int more_to_do;
>
> - RING_FINAL_CHECK_FOR_REQUESTS(&vif->tx, more_to_do);
> + more_to_do = RING_HAS_UNCONSUMED_REQUESTS(&vif->tx);
>
> if (more_to_do)
> napi_schedule(&vif->napi);
>
next prev parent reply other threads:[~2014-05-15 13:41 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-15 11:59 [PATCH net V2] xen-netback: don't move event pointer in TX credit timeout callback Wei Liu
2014-05-15 13:04 ` Jacek Konieczny
2014-05-15 13:33 ` Wei Liu
2014-05-15 13:58 ` Wei Liu
2014-05-15 14:13 ` Wei Liu
2014-05-15 14:47 ` Zoltan Kiss
2014-05-15 15:30 ` Wei Liu
2014-05-15 16:34 ` Zoltan Kiss
2014-05-15 16:53 ` Wei Liu
2014-05-15 17:03 ` Zoltan Kiss
2014-05-15 18:16 ` Wei Liu
2014-05-15 13:40 ` David Vrabel [this message]
2014-05-15 13:59 ` [Xen-devel] " Wei Liu
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