linux-kernel - Re: Linux 2.6.21-rc1

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Date:	Wed, 21 Feb 2007 18:07:44 +0100
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Daniel Walker <dwalker@...sta.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	mingo@...e.hu
Subject: Re: Linux 2.6.21-rc1

On Wed, 2007-02-21 at 08:24 -0800, Daniel Walker wrote:
> > The most interesting core change may be the dyntick/nohz one, where timer 
> > ticks will only happen when needed. It's been brewing for a _loong_ time, 
> > but it's in the standard kernel now as an option. 
> 
> On i386 I get the following,
> 
> TCP cubic registered                                                            
> NET: Registered protocol family 1                                               
> NET: Registered protocol family 17                                              
> Testing NMI watchdog ... CPU#0: NMI appears to be stuck (24->24)!               
> CPU#1: NMI appears to be stuck (0->0)!                                          
> CPU#2: NMI appears to be stuck (0->0)!                                          
> CPU#3: NMI appears to be stuck (0->0)!              
> 
> when I add nmi_watchdog=1 to my boot args which worked on prior kernels.
> On closer inspection it looks like arch/i386/kernel/io_apic.c :
> check_timer() --> timer_irq_works() depends on IRQ0 incrementing jiffies
> which is no longer the case AFAIK.

At this point the PIT / HPET _is_ active and incrementing jiffies. The
switch to local apic timers happens afterwards. 

> I'm not sure exactly how that relates to the NMI, but the check_timer()
> function disabled the NMI through the io-apic if it can't get the
> "timer" working through the io-apic.

Boot log please.

	tglx


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