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Date:      Wed, 27 Sep 2006 11:45:09 +0200
From:      "Patrick M. Hausen" <hausen@punkt.de>
To:        Scott Long <scottl@samsco.org>
Cc:        freebsd-stable@freebsd.org, Oliver Brandmueller <ob@e-Gitt.NET>
Subject:   Re: 6.2 SHOWSTOPPER - em completely unusable on 6.2
Message-ID:  <20060927094509.GB75104@hugo10.ka.punkt.de>
In-Reply-To: <451A4189.5020906@samsco.org>
References:  <451A1375.5080202@gneto.com> <20060927071538.GF22229@e-Gitt.NET> <451A4189.5020906@samsco.org>

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Hello!

> Well, the best I can say at the moment is, "Wow."  =-(  I guess the 
> thing to do here is to figure out if the problem lies with the em 
> interrupt handler not getting run, or the taskqueue not getting run.

I helped Pyun with some debugging by providing ssh access to
a machine showing the (seemingly) same problem.

At first he thought the interrupt handler of the em driver was
the culprit, but we applied quite a few patches and tested
afterwards - seems like the driver is not the cause.

On -stable occasionally other people complained about very similar
looking problems with bge and other drivers. My guess is, though 
I'm not a kernel developer, just an experienced admin, that
em stands out as problematic just by coincidence. Certain onboard
network components tend to come with certaiin chipsets and certain
architectures.

So, Pyun suggested it was a problem with the taskqueue that was
introduced some time between 6.0 and 6.1.

With my system (Tyan GT20 B5161G20) the problem shows when there
is heavy disk and cpu activity, like "make buildworld".
I made sure that the em interface doesn't share an interrupt
with the SATA controller. When the problem occurs, I get the
well known "watchdog timeout" messages and then the system's
network activity over that interface freezes completely for
a couple of minutes.
Usually the system recovers after a while without reboot or
other measures.

What I can do: give ssh access to a system showing this behaviour
including a network connection to another box, so one can transfer
large amounts of data over a private LAN. I used FTP of a sparse
big file.

Prerequisite: fixed IP address of the machine that the developer
whishes to use to connect to my system.

HTH,
Patrick
-- 
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