linux-kernel - Re: 2.6.28-rc9: oprofile regression

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Date:	Sat, 17 Jan 2009 15:14:53 +0100
From:	Robert Richter <robert.richter@....com>
To:	Tim Blechmann <tim@...ngt.org>
CC:	Thomas Gleixner <tglx@...utronix.de>,
	Andi Kleen <ak@...ux.intel.com>, oprofile-list@...ts.sf.net,
	linux-kernel@...r.kernel.org, venkatesh.pallipadi@...el.com
Subject: Re: 2.6.28-rc9: oprofile regression

On 17.01.09 14:32:49, Tim Blechmann wrote:
> hm, it seems a bit more complicated than i originally thought.
> 
> trying to reconstruct commit b99170288421c79f0c2efa8b33e26e65f4bb7fb8, i
> found, that resetting counter_width in ppro_setup_ctrs, causes the
> issue. reverting part of the patch, resolved the issue:
> 
> --- a/arch/x86/oprofile/op_model_ppro.c
> +++ b/arch/x86/oprofile/op_model_ppro.c
> @@ -79,8 +79,8 @@ static void ppro_setup_ctrs(struct op_msrs const * const msrs)
>         if (cpu_has_arch_perfmon) {
>                 union cpuid10_eax eax;
>                 eax.full = cpuid_eax(0xa);
> -               if (counter_width < eax.split.bit_width)
> -                       counter_width = eax.split.bit_width;
> +//             if (counter_width < eax.split.bit_width)
> +//                     counter_width = eax.split.bit_width;
>         }
>  
>         /* clear all counters */
> 
> 
> however, trying to apply this patch to 2.6.28, the behavior is the same
> as before (one NMI) ... so possibly, it is a combination of two bugs,
> with similar symptoms ... 

Tim, could you revert 7c64ade53a6f977d73f16243865c42ceae999aea too?

If this not helps, last chance is
59512900baab03c5629f2ff5efad1d5d4e682ece, but this seems to be save.

-Robert

-- 
Advanced Micro Devices, Inc.
Operating System Research Center
email: robert.richter@....com

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