From: Andi Kleen <ak@suse.de>
To: tglx@linutronix.de
Subject: Re: [patch 13/19] GTOD: Mark TSC unusable for highres timers
Date: Sat, 11 Nov 2006 14:51:33 +0100
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Cc: Andrew Morton <akpm@osdl.org>, Ingo Molnar <mingo@elte.hu>,
       john stultz <johnstul@us.ibm.com>, LKML <linux-kernel@vger.kernel.org>,
       Len Brown <lenb@kernel.org>, Arjan van de Ven <arjan@infradead.org>,
       Roman Zippel <zippel@linux-m68k.org>
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> > > And afaict the reason for that is that we're using jiffies to determine if
> > > the TSC has gone bad, and that test is getting false positives.
> > 
> > The i386 clocksource had always trouble with that. e.g.  I have a box
> > where the TSC works perfectly fine on a 64bit kernel, but since the new i386
> > clocksource code is in it always insists on disabling it shortly after boot.

shortly after boot means in user space here, not during the first idling.

> > My guess is that some of the checks in there are just broken and need
> > to be fixed.
> 
> It's the unconditional mark_unstable call in ACPI C2 state. /me looks.

The system doesn't support C2 states. It's an older single socket Athlon 64 
with VIA chipset. I haven't looked in detail on why it fails.

-Andi
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