linux-kernel - Re: [BUG] jiffies counter leaps in 2.6.24-rc3

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Message-ID: <20071129103511.GD10577@elte.hu>
Date:	Thu, 29 Nov 2007 11:35:11 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Stefano Brivio <stefano.brivio@...imi.it>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>, linux-kernel@...r.kernel.org,
	Michael Buesch <mb@...sch.de>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Len Brown <lenb@...nel.org>, Dave Jones <davej@...hat.com>
Subject: Re: [BUG] jiffies counter leaps in 2.6.24-rc3


* Stefano Brivio <stefano.brivio@...imi.it> wrote:

> Ok, I found out how to reliably reproduce this bug. The root session issue
> was a bit weird, but I noticed I usually switch to root only when I need to
> change the CPU frequency. And here's what happens:
> 
> # cpuspeedy min
> [after some time...]
> Nov 29 09:42:31 morte [ 4408.722597] b43-phy0 ERROR: PHY transmission error
> 
> # cpuspeedy max
> Nov 29 09:42:41 morte [ 1177.238599] wmaster0: STA 00:14:c1:35:8d:eb Average rate: 540 (2160/4)
> 
> It looks like jiffies get scaled exactly by a 3.75 factor, which is
> <max_frequency>/<min_frequency> here. I use acpi-cpufreq and this is my
> (only) CPU:
> processor       : 0
> vendor_id       : GenuineIntel
> cpu family      : 6
> model           : 13
> model name      : Intel(R) Pentium(R) M processor 1.50GHz
> stepping        : 6
> cpu MHz         : 1500.000
> cache size      : 2048 KB
> fdiv_bug        : no
> hlt_bug         : no
> f00f_bug        : no
> coma_bug        : no
> fpu             : yes
> fpu_exception   : yes
> cpuid level     : 2
> wp              : yes
> flags           : fpu vme de pse tsc msr mce cx8 sep mtrr pge mca cmov pat clflush dts acpi mmx fxsr sse sse2 ss tm pbe bts est tm2
> bogomips        : 2993.49
> clflush size    : 64
> 
> Any hint?

ah, the cpufreq/acpi/acpi-cpufreq angle is indeed a big clue. I've 
Cc:-ed various interested parties.

	Ingo
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