From mboxrd@z Thu Jan  1 00:00:00 1970
From: Greg Kroah-Hartman <gregkh-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org>
Subject: Re: [PATCH] device: separate all subsys mutexes (was: Re: [BUG]
 potential deadlock led by cpu_hotplug lock (memcg involved))
Date: Tue, 12 Mar 2013 08:43:41 -0700
Message-ID: <20130312154341.GB18852@kroah.com>
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To: Peter Zijlstra <peterz-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
Cc: Michal Hocko <mhocko-AlSwsSmVLrQ@public.gmane.org>, Li Zefan <lizefan-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>, LKML <linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, cgroups <cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, KAMEZAWA Hiroyuki <kamezawa.hiroyu-+CUm20s59erQFUHtdCDX3A@public.gmane.org>, Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>, Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>, Jiri Kosina <jkosina-AlSwsSmVLrQ@public.gmane.org>, Ingo Molnar <mingo-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, Kay Sievers <kay.sievers-tD+1rO4QERM@public.gmane.org>

On Tue, Mar 12, 2013 at 04:28:25PM +0100, Peter Zijlstra wrote:
> On Tue, 2013-03-12 at 14:05 +0100, Michal Hocko wrote:
> > @@ -111,17 +111,17 @@ struct bus_type {
> >         struct iommu_ops *iommu_ops;
> >  
> >         struct subsys_private *p;
> > +       struct lock_class_key __key;
> >  };
> 
> Is struct bus_type constrained to static storage or can people go an
> allocate this stuff dynamically? If so, this patch is broken.

I don't think anyone is creating this dynamically, it should be static.
Why does this matter, does the lockdep code care about where the
variable is declared (heap vs. static)?

thanks,

greg k-h