linux-kernel - Re: [PATCH 0/2] i386: Fix two more NMI watchdog bugs

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Date:	Fri, 8 Jun 2007 23:13:31 +0200
From:	"Udo A. Steinberg" <us15@...inf.tu-dresden.de>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Ingo Molnar <mingo@...e.hu>,
	Bj?rn Steinbrink <B.Steinbrink@....de>,
	Andi Kleen <andi@...stfloor.org>,
	Michal Piotrowski <michal.k.k.piotrowski@...il.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>, ak@...e.de
Subject: Re: [PATCH 0/2] i386: Fix two more NMI watchdog bugs

On Fri, 8 Jun 2007 13:57:27 -0700 Andrew Morton (AM) wrote:

AM> On Fri, 8 Jun 2007 22:49:11 +0200
AM> "Udo A. Steinberg" <us15@...inf.tu-dresden.de> wrote:
AM> 
AM> > On Fri, 8 Jun 2007 22:43:25 +0200 Ingo Molnar (IM) wrote:
AM> > 
AM> > IM> 
AM> > IM> * Bj?rn Steinbrink <B.Steinbrink@....de> wrote:
AM> > IM> 
AM> > IM> > Anyway, both are bugs and should be fixed. Maybe we're even lucky
AM> > IM> > and it fixes your hang. *fingers crossed*
AM> > IM> 
AM> > IM> just to make it clear: the NMI watchdog was working perfectly fine on 
AM> > IM> that box (in v2.6.21 and in dozens of kernel releases before that,
AM> > IM> for multiple years) before Andi's cleanup patch. So lets find that
AM> > IM> bug first or revert the cleanups.
AM> > IM> 
AM> > IM> 	Ingo
AM> > 
AM> > None of the patches posted by Bj__rn fix the kernel BUG at
AM> > arch/i386/kernel/cpu/perfctr-watchdog.c:126! that occurs when doing
AM> > echo 0 > /proc/sys/kernel/nmi_watchdog
AM> > 
AM> > Call Trace:
AM> >  [<c010c429>] single_msr_unreserve+0xd/0x1a
AM> >  [<c010c668>] disable_lapic_nmi_watchdog+0x27/0x35
AM> >  [<c0110ac6>] proc_nmi_enabled+0xa0/0xbd
AM> >  [<c018550c>] proc_sys_write+0x6f/0x8c
AM> >  [<c018549d>] proc_sys_write+0x0/0x8c
AM> >  [<c0156e5b>] vfs_write+0x8a/0x10c
AM> >  [<c0157317>] sys_write+0x41/0x67
AM> >  [<c0103c30>] syscall_call+0x7/0xb
AM> > 
AM> > Andi, did you have a patch for that?
AM> > 
AM> 
AM> This?
AM> 
AM> 
AM> From: Bjorn Steinbrink <B.Steinbrink@....de>
AM> 
AM> Fix oops triggered during: echo 0 > /proc/sys/kernel/nmi_watchdog
AM> 
AM> The culprit seems to be 09198e68501a7e34737cd9264d266f42429abcdc:

This alone does not help, but in combination with the other two patches 
the problem no longer occurs. 

Thanks,

	- Udo

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