Re: [Xen-devel] [PATCH net] xen-netback: fix vif tx queue race in xenvif_rx_interrupt

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: netdev-owner@xxxxxxxxxxxxxxx [mailto:netdev-
> owner@xxxxxxxxxxxxxxx] On Behalf Of David Miller
> Sent: 08 January 2014 20:12
> To: majieyue@xxxxxxxxx
> Cc: netdev@xxxxxxxxxxxxxxx; xen-devel@xxxxxxxxxxxxx; jieyue.majy@alibaba-
> inc.com; yingbin.wangyb@xxxxxxxxxxxxxxx; tienan.ftn@xxxxxxxxxxxxxxx; Wei
> Liu; Ian Campbell; David Vrabel
> Subject: Re: [PATCH net] xen-netback: fix vif tx queue race in
> xenvif_rx_interrupt
> 
> From: Ma JieYue <majieyue@xxxxxxxxx>
> Date: Thu,  9 Jan 2014 03:24:21 +0800
> 
> > -   if (xenvif_rx_schedulable(vif))
> > +   if (netif_queue_stopped(vif->dev) && xenvif_rx_schedulable(vif))
> 
> I do not see anything which prevents a netif_stop_queue() call from
> happening
> between these two tests in another thread of control.
> 
> This therefore looks like a bandaid and not a real fix.

My fix "xen-netback: improve guest-receive-side flow control" in net-next will 
make this change irrelevant as it completely removes all this somewhat fragile 
code.

  Paul

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