linux-kernel - Re: Fw: [BUG 2.6.21-rc7] acpi_pm clocksource loses time on x86-64

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Date:	Tue, 17 Apr 2007 13:12:44 -0700
From:	john stultz <johnstul@...ibm.com>
To:	mikpe@...uu.se
Cc:	Ingo Molnar <mingo@...e.hu>, Thomas Gleixner <tglx@...utronix.de>,
	Adrian Bunk <bunk@...sta.de>,
	lkml <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: Fw: [BUG 2.6.21-rc7] acpi_pm clocksource loses time on x86-64

On Tue, 2007-04-17 at 10:09 -0700, Andrew Morton wrote:
> I guess this counts as a regression.
> 
> Begin forwarded message:
> 
> Date: Tue, 17 Apr 2007 14:16:25 +0200 (MEST)
> From: Mikael Pettersson 	
> To: linux-kernel@...r.kernel.org
> Subject: [BUG 2.6.21-rc7] acpi_pm clocksource loses time on x86-64
> 
> 
> The machine is an old Athlon64 laptop (Targa Visionary 811,
> OEMd as the Arima W720-K8, also sold as the eMachines m6805)
> with a VIA K8T800 chipset. ACPI is enabled.
> 
> Up to kernel 2.6.20, time-keeping worked fine. In the
> x86-64 kernel, the clock source is listed as "jiffies".
> 
> With current 2.6.21-rc7, the x86-64 kernel selects
> acpi_pm as its clock source. Unfortunately, with this
> clock time drifts and it loses several minutes per hour.
> 
> What's strange is that the i386 kernel on the same
> machine (with similar .config) does not lose time
> while using the acpi_pm clock source.

Huh. Quite strange as its the same acpi_pm clocksource driver!

The only difference I see right off is that verify_pmtmr_rate() isn't
done on x86_64. Although I'd expect you'd see "PM-Timer running at
invalid rate" w/ the i386 kernel if it made a difference.

Could you send me the dmesg output for both the x86_64 and i386 kernels
you tried?

thanks
-john


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