linux-kernel - Re: [patch, 2.6.22-rc6] fix nmi

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Date:	Mon, 25 Jun 2007 15:13:40 +0200
From:	Björn Steinbrink <B.Steinbrink@....de>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
Cc:	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, Andi Kleen <andi@...stfloor.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Rusty Russell <rusty@...tcorp.com.au>
Subject: Re: [patch, 2.6.22-rc6] fix nmi_watchdog=2 bootup hang

On 2007.06.25 08:40:35 -0400, Jeremy Fitzhardinge wrote:
> Ingo Molnar wrote:
> >* Ingo Molnar <mingo@...e.hu> wrote:
> >
> >  
> >>hm, restoring nmi.c to the v2.6.21 state does not fix the 
> >>nmi_watchdog=2 hang. I'll do a bisection run.
> >>    
> >
> >and after spending an hour on 15 bisection steps:
> >
> > git-bisect start
> > git-bisect good d1be341dba5521506d9e6dccfd66179080705bea
> > git-bisect bad a06381fec77bf88ec6c5eb6324457cb04e9ffd69
> > git-bisect bad 794543a236074f49a8af89ef08ef6a753e4777e5
> > git-bisect good 24a77daf3d80bddcece044e6dc3675e427eef3f3
> > git-bisect bad ea62ccd00fd0b6720b033adfc9984f31130ce195
> > git-bisect good 7e20ef030dde0e52dd5a57220ee82fa9facbea4e
> > git-bisect bad f19cccf366a07e05703c90038704a3a5ffcb0607
> > git-bisect good 0d08e0d3a97cce22ebf80b54785e00d9b94e1add
> > git-bisect bad 856f44ff4af6e57fdc39a8b2bec498c88438bd27
> > git-bisect bad f8822f42019eceed19cc6c0f985a489e17796ed8
> > git-bisect good 1c3d99c11c47c8a1a9ed6a46555dbf6520683c52
> > git-bisect good b239fb2501117bf3aeb4dd6926edd855be92333d
> > git-bisect good 98de032b681d8a7532d44dfc66aa5c0c1c755a9d
> > git-bisect good 42c24fa22e86365055fc931d833f26165e687c19
> >
> >the winner is ...
> >
> > f8822f42019eceed19cc6c0f985a489e17796ed8 is first bad commit
> > commit f8822f42019eceed19cc6c0f985a489e17796ed8
> > Author: Jeremy Fitzhardinge <jeremy@...p.org>
> > Date:   Wed May 2 19:27:14 2007 +0200
> >
> >    [PATCH] i386: PARAVIRT: Consistently wrap paravirt ops callsites to 
> >    make them patchable
> >
> >... our wonderful paravirt subsystem, honed to eternal perfection by the 
> >testing-machine x86_64 tree.
> >
> >reverting -git-curr's paravirt.c, paravirt.h, smp.c and tlbflush.h to 
> >before the bad commit makes the NMI watchdog work again. Patch against 
> >-rc6 is below.
> >  
> 
> Er, wow.  I've been running with this stuff for months without a 
> problem.   Do you have CONFIG_PARAVIRT enabled?  Do you still get the 
> hang if you boot with "noreplace-paravirt" to disable the patching? 

Are you running on AMD hardware? As Intel performance counters are only
32 bits wide, the wrmsrl bug should be a non-issue at least for the NMI
watchdog on Intel hardware. AMD uses 48bit wide performance counters,
which are probably less happy ;-)

Björn
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