linux-kernel - Re: HPET regression in 2.6.26 versus 2.6.25 -- found another user with the same regression

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Date:	Fri, 22 Aug 2008 19:25:59 -0700 (PDT)
From:	David Witbrodt <dawitbro@...global.net>
To:	Yinghai Lu <yhlu.kernel@...il.com>
Cc:	Ingo Molnar <mingo@...e.hu>, Vivek Goyal <vgoyal@...hat.com>,
	Bill Fink <billfink@...dspring.com>,
	linux-kernel@...r.kernel.org,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>, netdev <netdev@...r.kernel.org>
Subject: Re: HPET regression in 2.6.26 versus 2.6.25 -- found another user with the same regression

Yinghai,

I finally found time to try to get some output using your patch for
resource.c on a kernel that hangs.

Some really good advice came in earlier today:  I can use "vga=1" to
get 80x50 mode during the early boot sequence.  I used that, and made
some alterations to the changes in your patch to squeeze more info
onto the screen.  I also changed KERN_DEBUG to KERN_ERR in your
printk's so that I could decrease the other output by using 
"loglevel=4".

While I cannot see the entire set of output from your debug printk's,
I can see the last 45+ lines that appear before the hang.  The results
were the same as when I used "hpet=disable":  the only difference 
between the working 2.6.25 kernel and the hanging 2.6.27 kernel was 
that the resource named "0000:00:14.0" (fed00000-fed003ff) switched
from "conflict=0" to "conflict=1".

The output from 'cat /proc/iomem' on a non-hanging kernel included
these two lines:

fed00000-fed003ff : HPET 0
  fed00000-fed003ff : 0000:00:14.0

None of this is really new information, since it matches with info
I've already posted.  I just wanted to let you know the results of
your patch on a kernel that hangs.

If I find a way to read the info from the 15-20 lines that scroll 
away on me, and if I find a difference, I'll post that as well.

DW
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