Date: Fri, 15 Aug 2008 15:26:46 +0200
From: Ingo Molnar <mingo@elte.hu>
To: David Witbrodt <dawitbro@sbcglobal.net>
Cc: Yinghai Lu <yhlu.kernel@gmail.com>, linux-kernel@vger.kernel.org,
       "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
       Peter Zijlstra <peterz@infradead.org>,
       Thomas Gleixner <tglx@linutronix.de>, "H. Peter Anvin" <hpa@zytor.com>,
       netdev <netdev@vger.kernel.org>
Subject: Re: HPET regression in 2.6.26 versus 2.6.25 -- question about NMI
	watchdog
Message-ID: <20080815132646.GF30597@elte.hu>
References: <445817.22956.qm@web82101.mail.mud.yahoo.com>
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* David Witbrodt <dawitbro@sbcglobal.net> wrote:

> Quick question: a quick browse of 'Documentation/nmi_watchdog.txt' 
> suggests that I should use "nmi_watchdog=1", since I have SMP (CPU = 
> Athlon 64 X2, with CONFIG_SMP=y).  Should I follow your suggestion 
> later, or follow the recommendation of the 'nmi_watchdog.txt' doc?

you could try both, starting with nmi_watchdog=2 - and trying 
nmi_watchdog=1 if that doesnt work. The problem with nmi_watchdog=1 is 
that it disables high-res timers. (because it has to - it piggy-backs on 
the back of a periodic timer interrupt)

you might even want to test the NMI watchdog with an intentional 
user-space hard lockup - with the attached lockupcli.c program. 
(Warning: if you run it as root it will really lock up your box hard. 
Run it from a VGA text mode console to see any console messages.)

	Ingo

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main ()
{
	iopl(3);
	for (;;) asm("cli");
}


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