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Date: Fri, 20 Jul 2007 15:59:12 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Greg KH <gregkh@suse.de>
Cc: Michal Piotrowski <michal.k.k.piotrowski@gmail.com>,
       LKML <linux-kernel@vger.kernel.org>
Subject: Re: [broken-out-2007-07-20-00-22] kernel bug at kernel/params:570
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On Fri, 20 Jul 2007 15:50:47 -0700
Greg KH <gregkh@suse.de> wrote:

> On Fri, Jul 20, 2007 at 06:32:21PM +0200, Michal Piotrowski wrote:
> >  Hi Greg,
> > 
> >  This looks like a sysfs bug
> >  http://www.stardust.webpages.pl/files/tbf/bitis-gabonica/broken-out-2007-07-20-00-22/00003.jpg
> > 
> >  l *kernel_param_sysfs_setup+0x75
> >  0xc13c0894 is in kernel_param_sysfs_setup (kernel/params.c:570).
> >  565             mk->mod = THIS_MODULE;
> >  566             kobj_set_kset_s(mk, module_subsys);
> >  567             kobject_set_name(&mk->kobj, name);
> >  568             kobject_init(&mk->kobj);
> >  569             ret = kobject_add(&mk->kobj);
> >  570             BUG_ON(ret < 0);
> >  571             param_sysfs_setup(mk, kparam, num_params, name_skip);
> >  572             kobject_uevent(&mk->kobj, KOBJ_ADD);
> >  573     }
> >  574
> > 
> >  http://www.stardust.webpages.pl/files/tbf/bitis-gabonica/broken-out-2007-07-20-00-22/mm-config
> 
> What kernel version is this happening on?  The -mm tree?  Can you try
> Linus's tree instead?
> 
> It looks like there was some needed information right before the first
> stack dump, showing exactly what kobject was trying to be added that was
> already present.  Odds are this is a kernel parameter with the same name
> as a duplicate one within the same module, but the trick is going to be
> trying to figure out what module is causing this.
> 
> So it's not a sysfs bug, but rather a driver issue that this is
> catching.

In that case a BUG was way too harsh treatment, and in fact directly
contributed to our inability to debug the bug!

Can we wind that back a bit?  Add some useful printks and then recover
in some fashion?