netdev - Re: [PATCH 1/3] xen-netback: make feature-rx-notify mandatory

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Message-ID: <20141023114453.GH9188@zion.uk.xensource.com>
Date:	Thu, 23 Oct 2014 12:44:53 +0100
From:	Wei Liu <wei.liu2@...rix.com>
To:	David Vrabel <david.vrabel@...rix.com>
CC:	Wei Liu <wei.liu2@...rix.com>, <netdev@...r.kernel.org>,
	<xen-devel@...ts.xenproject.org>,
	Ian Campbell <ian.campbell@...rix.com>
Subject: Re: [PATCH 1/3] xen-netback: make feature-rx-notify mandatory

On Thu, Oct 23, 2014 at 12:37:54PM +0100, David Vrabel wrote:
> On 23/10/14 12:32, Wei Liu wrote:
> > On Thu, Oct 23, 2014 at 12:16:29PM +0100, Wei Liu wrote:
> >> On Wed, Oct 22, 2014 at 02:08:53PM +0100, David Vrabel wrote:
> >>> Frontends that do not provide feature-rx-notify may stall because
> >>> netback depends on the notification from frontend to wake the guest Rx
> >>> thread (even if can_queue is false).
> >>>
> >>> This could be fixed but feature-rx-notify was introduced in 2006 and I
> >>> am not aware of any frontends that do not implement this.
> >>>
> >>> Signed-off-by: David Vrabel <david.vrabel@...rix.com>
> >>
> >> Acked-by: Wei Liu <wei.liu2@...rix.com>
> > 
> > While I can understand this patch by itself, can you elaborate a little
> > bit on how it affects later patches? Because what I'm thinking is that
> > this patch is not for stable while other two should go to stable.
> 
> >From the cover letter:
> 
> "The first patch is a prerequite.  Removing support for frontends with
> feature-rx-notify makes it easier to reason about the correctness of
> netback since it no longer has to support this outdated and broken
> mode."
> 

I saw that.

I think you should make it a little bit clearer.

The queue is not guaranteed to stop if we keep this feature.

> The other patches do not meet the stable kernel requirements (they're
> too long one thing).
> 

Does length matter? I surely had written long patch for stable.

Wei.

> David
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