linux-kernel - Re: [PATCH -v2] perf, x86: try to handle unknown nmis with running perfctrs

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Date:	Mon, 16 Aug 2010 23:18:46 +0400
From:	Cyrill Gorcunov <gorcunov@...il.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Robert Richter <robert.richter@....com>,
	Don Zickus <dzickus@...hat.com>,
	Lin Ming <ming.m.lin@...el.com>, Ingo Molnar <mingo@...e.hu>,
	"fweisbec@...il.com" <fweisbec@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Huang, Ying" <ying.huang@...el.com>,
	Yinghai Lu <yinghai@...nel.org>,
	Andi Kleen <andi@...stfloor.org>
Subject: Re: [PATCH -v2] perf, x86: try to handle unknown nmis with running
	perfctrs

On Mon, Aug 16, 2010 at 09:13:16PM +0200, Peter Zijlstra wrote:
> On Mon, 2010-08-16 at 23:06 +0400, Cyrill Gorcunov wrote:
> > I never heard of backward running tsc, though tsc is a strange beast.
> > 
> Its not supposed to happen, but then there's BIOS failure-add that frobs
> the TSC from SMIs and fun TSC artifacts around CPU frequency changes and
> people resetting TSC in S-states etc..

grr :/

> 
> In short, never trust the TSC to be even remotely sane.
> 

ok, good to know, thanks!

	-- Cyrill
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