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

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Message-ID: <1281985996.1926.1848.camel@laptop>
Date:	Mon, 16 Aug 2010 21:13:16 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Cyrill Gorcunov <gorcunov@...il.com>
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, 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..

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