linux-kernel - Re: [Xen-devel] [PATCH resend] xen-netback: switch to threaded irq for control ring

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Date:   Thu, 22 Sep 2016 12:39:24 +0200
From:   Juergen Gross <jgross@...e.com>
To:     Paul Durrant <Paul.Durrant@...rix.com>,
        "xen-devel@...ts.xenproject.org" <xen-devel@...ts.xenproject.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Cc:     Wei Liu <wei.liu2@...rix.com>
Subject: Re: [Xen-devel] [PATCH resend] xen-netback: switch to threaded irq
 for control ring

On 22/09/16 12:31, Paul Durrant wrote:
>> -----Original Message-----
>> From: Juergen Gross [mailto:jgross@...e.com]
>> Sent: 22 September 2016 11:17
>> To: Paul Durrant <Paul.Durrant@...rix.com>; xen-devel@...ts.xenproject.org;
>> netdev@...r.kernel.orga <netdev@...r.kernel.org>; linux-
>> kernel@...r.kernel.org
>> Cc: Wei Liu <wei.liu2@...rix.com>
>> Subject: Re: [Xen-devel] [PATCH resend] xen-netback: switch to threaded irq
>> for control ring
>>
>> On 22/09/16 11:09, Paul Durrant wrote:
>>>> -----Original Message-----
>>>> From: Xen-devel [mailto:xen-devel-bounces@...ts.xen.org] On Behalf Of
>>>> Juergen Gross
>>>> Sent: 22 September 2016 10:03
>>>> To: xen-devel@...ts.xenproject.org; netdev@...r.kernel.orga; linux-
>>>> kernel@...r.kernel.org
>>>> Cc: Juergen Gross <jgross@...e.com>; Wei Liu <wei.liu2@...rix.com>
>>>> Subject: [Xen-devel] [PATCH resend] xen-netback: switch to threaded
>>>> irq for control ring
>>>>
>>>> Instead of open coding it use the threaded irq mechanism in xen-netback.
>>>>
>>>> Signed-off-by: Juergen Gross <jgross@...e.com>
>>>
>>> How have you tested this change?
>>
>> Only compile-tested and loaded the module. As this feature isn't being used
>> in linux netfront AFAIK it is not easily testable. OTOH the code modification is
>> rather limited and I've used the threaded irq in the Xen scsiback driver
>> myself, so I'm rather confident it will work.
>>
> 
> OK. How about doing the rx interrupt/task too so that it can be easily tested with a linux netfront?

I'd like to, but this would require some more work. The rx kthread isn't
activated by an event only, but by a timer, too. This isn't easy to map
to the threaded irq framework. If, however, you are confident the timer
isn't really necessary I'd be happy to provide a patch switching the
rx task to the threaded irq, too.

And to be honest: this wouldn't verify that the control ring related
patch is really working. The mechanism itself _is_ working as it is
already in use in xen-scsiback in a very similar environment.


Juergen