linux-kernel - Re: nmi_watchdog=2 regression in 2.6.21

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Message-ID: <20070831162146.GD7161@frankl.hpl.hp.com>
Date:	Fri, 31 Aug 2007 09:21:46 -0700
From:	Stephane Eranian <eranian@....hp.com>
To:	Daniel Walker <dwalker@...sta.com>
Cc:	B.Steinbrink@....de, ak@...e.de, linux-kernel@...r.kernel.org,
	akpm@...ux-foundation.org, Stephane Eranian <eranian@....hp.com>
Subject: Re: nmi_watchdog=2 regression in 2.6.21

Daniel,

On Fri, Aug 31, 2007 at 07:43:20AM -0700, Daniel Walker wrote:
> On Thu, 2007-08-30 at 14:05 -0700, Stephane Eranian wrote:
> > Daniel,
> 
> > Yes, I realized I missed a small detail in the switch statement.
> > Could you try the new version?
> 
> This patch still has the stuck NMI .. Essentially the same thing that
> happened without the patch..
> 
Ok, looks like deaulting to P6 does not quite work.

Here is a new version. This time I used a different approach.
I am must admit I am a bit puzzled by the duplication of information
between the wd_ops and the nmi_watchdog_ctlblk structure. My understanding
is that thelater is used as a cache for the info that needs to be per-cpu.

The wd_ops provides the MSR to use for the counter, yet all the setup_*()
routines hardcode the MSR. Not sure why?

In this patch, the setup_*() routine now extract the MSR from the wd_ops
to copy them into the nmi_watchdog_ctlblk. This is not done for P4 because
of the special and ugly case of HT. 

With this approach, we can now create a custom wd_ops for CoreDuo that is
a clone of the intel_arch_wd_ops, except for the MSR.

Could you try this one instead?

Thanks.

-- 

-Stephane

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