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Subject: Re: [patch] Declare explicit, hardware based lock ranking in serio
From: Arjan van de Ven <arjan@linux.intel.com>
To: Dmitry Torokhov <dtor_core@ameritech.net>
Cc: Andrew Morton <akpm@osdl.org>, linux-kernel@vger.kernel.org,
       mingo@redhat.com, arjanv@redhat.com, Linux Portal <linportal@gmail.com>
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Date: Sat, 03 Jun 2006 14:11:17 +0200
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On Sat, 2006-06-03 at 07:56 -0400, Dmitry Torokhov wrote:
> On Saturday 03 June 2006 04:50, Arjan van de Ven wrote:
> > > Thanks.
> > > 
> > > So we're taking ps2->cmd_mutex and then we're recurring back into
> > > ps2_command() and then taking ps2->serio->cmd_mutex.
> > > 
> > > I suspect that's all correct/natural/expected and needs another
> > > make-lockdep-shut-up patch.
> > 
> > 
> > The PS/2 code has a natural device order and there is a one level
> > recursion in this device order in terms of the cmd_mutex; annotate 
> > this explicit recursion as ok
> > 
> 
> It is not necessarily single depth - one could have 2 or more pass-through
> ports chained together, although currently in kernel we only have Synaptics
> pass-through. If we were ever to implement pass-through port for IBMs
> trackpoints then we'd have:
> 
> 	Synaptics<->pass-through<->TP<->pass-through<->some mouse

is there a bound to this? lockdep can deal with upto 8 or so
recursions....