From: Dmitry Torokhov <dtor_core@ameritech.net>
To: Vojtech Pavlik <vojtech@suse.cz>
Subject: Re: [2.6 RFC/PATCH] Input: possible deadlock in i8042
Date: Sun, 30 Nov 2003 04:19:28 -0500
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Cc: linux-kernel@vger.kernel.org, Vojtech Pavlik <vojtech@suse.cz>,
       Andrew Morton <akpm@osdl.org>
References: <200311300303.57654.dtor_core@ameritech.net> <20031130090009.GA17038@ucw.cz>
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On Sunday 30 November 2003 04:00 am, Vojtech Pavlik wrote:
> On Sun, Nov 30, 2003 at 03:03:57AM -0500, Dmitry Torokhov wrote:
> > If request_irq fails in i8042_open it will call
> > serio_unregister_port, which takes serio_sem. i8042_open may be
> > called:
> >
> > serio_register_port - serio_find_dev - dev->connect
> > serio_register_device - dev->connect
> >
> > Both serio_register_port and serio_register_device take serio_sem as
> > well.
> >
> > I think that serio_{register|unregister}_port can be converted into
> > submitting requests to kseriod thus removing deadlock on the
> > serio_sem.
> >
> > The patch below is on top of serio* patches in Andrew Morton's -mm
> > tree.
>
> It's nice to avoid the deadlock this way, but I think it's not a good
> idea to make the register/unregister asynchronous - it could be a nasty
> surprise for an unsuspecting driver writer.
>

Serio_register_port is not guaranteed to find a driver for the serio anyway
as the driver can be compiled as a module and loaded much much later so it
should not be a concern. It is somewhat asynchronous already.

Dmitry
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