Re: [patch] Declare explicit, hardware based lock ranking in serio

[Dmitry Torokhov <dtor_core@ameritech.net>]

On Saturday 03 June 2006 08:11, Arjan van de Ven wrote:
> 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....
> 
 
Theoretically - no, practically - 2 as shown above. At the moment the
only devices that are using/may be using pass-through ports are Synaptics
touchpad and IBM trackpoint.

-- 
Dmitry