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Date: Thu, 6 Aug 2009 08:34:38 -0500 (CDT)
From: Larry Rosenman <ler@lerctr.org>
To: Robert Watson <rwatson@FreeBSD.org>
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Cc: jeff@FreeBSD.org, "Bjoern A. Zeeb" <bz@FreeBSD.org>,
	freebsd-current@freebsd.org, kib@FreeBSD.org,
	Navdeep Parhar <np@FreeBSD.org>,
	Navdeep Parhar <nparhar@gmail.com>, lstewart@FreeBSD.org
Subject: Re: reproducible panic in netisr
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On Thu, 6 Aug 2009, Robert Watson wrote:

> On Tue, 4 Aug 2009, Navdeep Parhar wrote:
>
>>>> This occurs on today's HEAD + some unrelated patches.  That makes it 
>>>> 8.0BETA2+ code.  I haven't tried older builds.
>>> 
>>> We have finally been able to reproduce this ourselves yesterday and
>> 
>> Well, it happens every single time on all of my amd64 machines. After I'd 
>> already sent my email I noticed that the netisr mutex has an odd address 
>> (pun intended :-))
>> 
>> m=0xffffffff8144d867
>
> Heh, indeed.  We just spotted the same result here.  In this case it's 
> causing a panic because it leads to a non-atomic read due to mtx_lock 
> spanning a cache line boundary, followed shortly by a panic because it's not 
> a valid thread pointer when it's dereferenced, as we get a fractional 
> pointer.
[snip]

Do we have an ETA for a testable patch?


-- 
Larry Rosenman                     http://www.lerctr.org/~ler
Phone: +1 512-248-2683                 E-Mail: ler@lerctr.org
US Mail: 430 Valona Loop, Round Rock, TX 78681-3893