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Date: Wed, 17 Oct 2007 19:39:02 +0200
From: Kris Kennaway <kris@FreeBSD.org>
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To: Bengt Ahlgren <bengta@sics.se>
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Cc: stable@freebsd.org
Subject: Re: Reproducable, possibly NFS related,
	fatal double fault in 6.2-R-p7
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Bengt Ahlgren wrote:
> Esa Karkkainen <ejk@iki.fi> writes:
> 
>> On Sun, Oct 14, 2007 at 02:37:23PM +0200, Kris Kennaway wrote:
>>> Esa Karkkainen wrote:
>>>> 	I get "Fatal double fault" error when writing to a filesystem
>>>> mounted from NFS server.
>> I got an offlist reply in which he suggested that the problem might be
>> in nve driver.
> 
> That was me.  I indeed got the same fault when running NFS over nve.
> Switching to nfe solved the problem for me.  The on-screen backtrace
> reveals the true location of the problem.  See:
> 
> http://www.sics.se/~bengta/FBSD/DSC00585.JPG
> 
> I do have a dump, but for some reason kgdb is not able to show the
> same information.

If you're using a module you have to do extra (but documented) steps. 
Or maybe kgdb has forgotten how to decode a double fault.

Anyway, this information is indeed definitive, and it's what others 
seeing this problem need to provide if they still have doubts.

Kris