netdev - Re: Hang: 2.6.32.4 sky2/DMAR (was [PATCH] sky2: Fix WARNING: at lib/dma-debug.c:902 check

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Date:	Sat, 23 Jan 2010 00:46:56 +0100
From:	Jarek Poplawski <jarkao2@...il.com>
To:	Michael Breuer <mbreuer@...jas.com>
Cc:	David Miller <davem@...emloft.net>,
	Stephen Hemminger <shemminger@...ux-foundation.org>,
	akpm@...ux-foundation.org, flyboy@...il.com,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	Michael Chan <mchan@...adcom.com>,
	Don Fry <pcnet32@...izon.net>,
	Francois Romieu <romieu@...zoreil.com>,
	Matt Carlson <mcarlson@...adcom.com>
Subject: Re: Hang: 2.6.32.4 sky2/DMAR (was [PATCH] sky2: Fix WARNING: at
 lib/dma-debug.c:902 check_sync)

On Fri, Jan 22, 2010 at 06:25:12PM -0500, Michael Breuer wrote:
> On 1/22/2010 6:06 PM, Jarek Poplawski wrote:
> >On Fri, Jan 22, 2010 at 05:14:58PM -0500, Michael Breuer wrote:
> >>Not sure I can do that. Note that based on the log messages, there
> >>were no errors/dropped packets involving dhcp. Moving the dhcp
> >>server off of the affected machine is not trivial. The dhcp
> >>correlation is based on logged messages preceding each crash. I
> >>cannot confirm that they're related, however it's really suspicious.
> >>If it helps, HP replaced my unmanaged switch with a managed one so I
> >>can see whether there were any switch events logged the next time I
> >>have a crash.
> >>
> >>At this point, it seems the following is required to trigger the crash:
> >>1) Uptime of 24-36 hours
> >>2) High RX load on server (cifs traffic is what I've triggered it with).
> >>3) Normal DHCP traffic.
> >Do you mean you got these crashes with the new switch too, and this
> >switch doesn't drop DHCP at all? (Otherwise, let's try this switch
> >first.)
> >
> >Jarek P.
> Nope - just got the new switch. Crash was old switch. That said, I
> don't think (based on the log messages) that the dhcpoffer packet
> drop was happening prior to the crash. I also can't fathom why a
> DHCPOFFER packet dropped after leaving the server would have any
> bearing on the issue.

You wrote earlier:
> [...] Also, there is always a dhcp exchange of some sort
> preceding the event.

So, I'm not sure there was "3) Normal DHCP traffic." if the switch
could drop DHCP packets in some buggy conditions. Anyway, let's try
the new one with really "3) Normal DHCP traffic.", I hope.

Jarek P.
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