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Subject: Re: 2.6.12-mm1 boot failure on NUMA box.
From: Lee Revell <rlrevell@joe-job.com>
To: "Martin J. Bligh" <mbligh@mbligh.org>
Cc: Ingo Molnar <mingo@elte.hu>, Andrew Morton <akpm@osdl.org>,
       linux-kernel@vger.kernel.org, Con Kolivas <kernel@kolivas.org>
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Date: Sat, 25 Jun 2005 14:08:25 -0400
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On Fri, 2005-06-24 at 23:42 -0700, Martin J. Bligh wrote:
> > (btw., if the TSC is that unreliable on numaq boxes, shouldnt we disable 
> > it for userspace apps too? Or are those hangs purely kernel bugs? In 
> > which case it might make sense to debug those a bit more - large-scale 
> > TSC unsyncedness is something that could slip in on other hardware too.)
> 
> Well it reads reliably. it just reliably reads utter random crap (well,
> across CPUs). Not many things read tsc from userspace, and it won't hang
> I guess .... depends what their expecations are. I do like gettimeofday
> not to go backwards though - that tends to bugger things up ;-)

The userspace apps that read the TSC know what they are doing, and have
chosen to use the TSC because they need a cheap, fast timer rather than
a correct one.  Please don't break it.

Lee