linux-kernel - Re: frequent lockups in 3.18rc4

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Message-ID: <20141203204439.GA5019@redhat.com>
Date:	Wed, 3 Dec 2014 15:44:39 -0500
From:	Dave Jones <davej@...hat.com>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	John Stultz <john.stultz@...aro.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Chris Mason <clm@...com>,
	Mike Galbraith <umgwanakikbuti@...il.com>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Dâniel Fraga <fragabr@...il.com>,
	Sasha Levin <sasha.levin@...cle.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: frequent lockups in 3.18rc4

On Wed, Dec 03, 2014 at 09:37:10PM +0100, Thomas Gleixner wrote:
 
 > Right, that resulted in a delta > 0. I have no idea how we could
 > create a negative delta via wrapping the HPET around, i.e. HPET being
 > 96 seconds ahead of TSC.
 > 
 > This looks more like a genuine TSC wreckage. So we have these possible
 > causes:
 > 
 >    1) SMI
 > 
 >    2) Power states
 > 
 >    3) Writing to the wrong MSR
 > 
 > So I assume that 1/2 are a non issue. They should surface in normal
 > non fuzzed operation as well.
 > 
 > Dave, does that TSC unstable thing always happen AFTER you started
 > fuzzing? If yes, what is the fuzzer doing this time?

I've seen it even after doing just a kernel build sometimes, It's
happened so regularly I've just assumed "the tsc is crap on this box".

On occasion I even see it shortly after boot, while idle.

	Dave

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