From: "Rafael J. Wysocki" <rjw@sisk.pl>
To: Greg KH <greg@kroah.com>, "Langsdorf, Mark" <mark.langsdorf@amd.com>
Subject: Re: Warning in during hotplug on 2.6.27-rc2-git5
Date: Sat, 16 Aug 2008 23:34:12 +0200
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Cc: Andi Kleen <andi@firstfloor.org>, linux-kernel@vger.kernel.org,
       Ingo Molnar <mingo@elte.hu>, Andrew Morton <akpm@linux-foundation.org>
References: <200808141753.58547.rjw@sisk.pl> <200808162128.25330.rjw@sisk.pl> <20080816201813.GA30715@kroah.com>
In-Reply-To: <20080816201813.GA30715@kroah.com>
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On Saturday, 16 of August 2008, Greg KH wrote:
> On Sat, Aug 16, 2008 at 09:28:24PM +0200, Rafael J. Wysocki wrote:
> > On Thursday, 14 of August 2008, Langsdorf, Mark wrote:
> > > > On Thu, Aug 14, 2008 at 05:53:57PM +0200, Rafael J. Wysocki wrote:
> > > > > On Wednesday, 13 of August 2008, Mark Langsdorf wrote:
> > > > > > I'm seeing the following error message when I hotunplug and replug
> > > > > > a cpu in 2.6.27-rc2-git5.  The system becomes unstable almost
> > > > > > immediately afterwards.
> > > > > 
> > > > > Hm, it seems that MCE is involved somehow.  Andi, can you 
> > > > have a look at this,
> > > > > please?
> > > > 
> > > > FWIW the mce code here actually hasn't changed for a long time.
> > > > 
> > > > 
> > > > > > ------------[ cut here ]------------
> > > > > > WARNING: at fs/sysfs/dir.c:463 sysfs_add_one+0x33/0x39()
> > > > > > sysfs: duplicate filename 'machinecheck4' can not be created
> > > > 
> > > > The only way I could see that happening if CPU_DEAD/CPU_ONLINE
> > > > is not properly balanced.
> > > 
> > > I'm still seeing it on 2.6.27-rc2, even with the 
> > > patch here http://lkml.org/lkml/2008/7/30/171 and the
> > > wbinvd_halt code patch applied.  Maybe something else
> > > broke in some of the recent hotplug changes?
> > 
> > My guess is that MCE does somthing that is not allowed by sysfs any more.
> 
> Hm, sysfs hasn't changed any in 2.6.27-rcX that I know of.

Hmm.  Mark, what kind of a system is this?  Is it a 2 quad-core CPU system
or similar ('machinecheck4' in your trace seems to imply something like this)?

Rafael
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