linux-kernel - Re: [PATCH] x86: sysctl to allow panic on IOCK NMI error

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Date:	Fri, 3 Jul 2009 11:24:05 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Kurt Garloff <garloff@...e.de>,
	"Maciej W. Rozycki" <macro@...ux-mips.org>,
	Greg KH <gregkh@...e.de>, x86@...nel.org,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org, Yinghai Lu <yinghai@...nel.org>,
	Jesse Barnes <jbarnes@...tuousgeek.org>
Subject: Re: [PATCH] x86: sysctl to allow panic on IOCK NMI error


* Kurt Garloff <garloff@...e.de> wrote:

> Ingo,
> 
> On Wed, Jul 01, 2009 at 01:10:03PM +0200, Ingo Molnar wrote:
> > * Maciej W. Rozycki <macro@...ux-mips.org> wrote:
> > 
> > > On Tue, 30 Jun 2009, Greg KH wrote:
> > > 
> > > > >  These days an IOCK NMI typically happens in response to a PCI 
> > > > > SERR -- it may be useful to traverse PCI buses to find the 
> > > > > offender and dump this information on this occasion too.  The 
> > > > > south bridge may have additional status too.
> > > > 
> > > > Sure, that would be great to have.  Care to make a patch?  :)
> > > 
> > >  ENOTIME, sorry.  Next year perhaps.  Or a homework project for 
> > > one of the newbies. ;)
> > 
> > You know that this project would kill a newbie, right? :)
> > 
> > We have no real southbridge drivers on x86 - but we should 
> > certainly add some. Also, walking the PCI device tree from NMI 
> > context is tricky as the lists there are not NMI safe - we could 
> > crash if we happen to get a #IOCK while loading/unloading 
> > drivers (which is rare but could happen).
> 
> Well -- in case we panic the system anyway this is not necessarily 
> a big issue (let's print the message before ...) -- if we crash 
> trying to gather additional info, we'll lose the info. Currently 
> we never have the info ...

We dont _necessarily_ crash ... The crash/panic is default off and 
sysctl driven.

Allowing a crash is not the highest quality of implementation and 
i'm somewhat wary of 'allow a little bit of crap' arguments - it's 
too similar to the 'little bit pregnant' concept ;-)

	Ingo
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