netdev - Re: [PATCH 17/20][BNX2]: Enhance the heartbeat.

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Message-ID: <4638400D.5010306@garzik.org>
Date:	Wed, 02 May 2007 03:38:53 -0400
From:	Jeff Garzik <jeff@...zik.org>
To:	David Miller <davem@...emloft.net>
CC:	mchan@...adcom.com, netdev@...r.kernel.org
Subject: Re: [PATCH 17/20][BNX2]: Enhance the heartbeat.

David Miller wrote:
> From: Jeff Garzik <jeff@...zik.org>
> Date: Wed, 02 May 2007 03:17:20 -0400
> 
>> Michael Chan wrote:
>>> [BNX2]: Enhance the heartbeat.
>>>
>>> In addition to the periodic heartbeat, we're adding a heartbeat
>>> request interrupt when the heartbeat is late.  This is useful
>>> especially in -rt kernels where the timer frequently runs late.
>>>
>>> Signed-off-by: Michael Chan <mchan@...adcom.com>
>> Should we really be adding code for such a special situation to upstream 
>> code?
>>
>> I lean towards "no", but defer to your and DaveM's judgement here.
> 
> My understanding of this situation is that if the timer is delayed a
> lot, which can happen with the -rt kernel, we don't send the heartbeat
> ping to the chip within the required margin.
> 
> If the margin is not met, the ASF firmware takes this as a signal that
> the host system is down, and does things like reset the network card
> and other things we don't want it to do.

Thanks for the explanation.

My main concern was

* adding code to use a kernel facility
* then, adding code to handle when that kernel facility doesn't work

and also

* adding code for a situation that never occurs in the upstream kernel.

Regards,

	Jeff


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