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Date: Tue, 12 Mar 2013 08:43:41 -0700
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Michal Hocko <mhocko@suse.cz>, Li Zefan <lizefan@huawei.com>,
        LKML <linux-kernel@vger.kernel.org>, cgroups <cgroups@vger.kernel.org>,
        linux-mm@kvack.org, KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Jiri Kosina <jkosina@suse.cz>, Ingo Molnar <mingo@redhat.com>,
        Kay Sievers <kay.sievers@vrfy.org>
Subject: Re: [PATCH] device: separate all subsys mutexes (was: Re: [BUG]
 potential deadlock led by cpu_hotplug lock (memcg involved))
Message-ID: <20130312154341.GB18852@kroah.com>
References: <513ECCFE.3070201@huawei.com>
 <20130312101555.GB30758@dhcp22.suse.cz>
 <20130312110750.GC30758@dhcp22.suse.cz>
 <20130312130504.GD30758@dhcp22.suse.cz>
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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