Re: [Xen-devel] [PATCH net-next v2] xen-netback: Rework rx_work_todo

[Zoltan Kiss <zoltan.kiss@xxxxxxxxxx>]

On 20/01/14 16:38, Wei Liu wrote:
> On Wed, Jan 15, 2014 at 05:11:07PM +0000, Zoltan Kiss wrote:
> > The recent patch to fix receive side flow control (11b57f) solved the spinning
> > thread problem, however caused an another one. The receive side can stall, if:
> > - [THREAD] xenvif_rx_action sets rx_queue_stopped to true
> > - [INTERRUPT] interrupt happens, and sets rx_event to true
> > - [THREAD] then xenvif_kthread sets rx_event to false
> > - [THREAD] rx_work_todo doesn't return true anymore
> >
> > Also, if interrupt sent but there is still no room in the ring, it take quite a
> > long time until xenvif_rx_action realize it. This patch ditch that two variable,
> > and rework rx_work_todo. If the thread finds it can't fit more skb's into the
> > ring, it saves the last slot estimation into rx_last_skb_slots, otherwise it's
> > kept as 0. Then rx_work_todo will check if:
> > - there is something to send to the ring (like before)
> > - there is space for the topmost packet in the queue
> >
> > I think that's more natural and optimal thing to test than two bool which are
> > set somewhere else.
> >
> > Signed-off-by: Zoltan Kiss <zoltan.kiss@xxxxxxxxxx>
> Sorry for the delay.
>
> Paul, thanks for reviewing.
>
> Acked-by: Wei Liu <wei.liu2@xxxxxxxxxx>
Hi,

This patch haven't made it to net-next yet, maybe because the subject 
doesn't suggest that this is a bugfix. I suggest to apply it as soon as 
possible, otherwise netback will be quite broken.
Zoli


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