From: Vojtech Pavlik <vojtech@suse.cz>
To: Dmitry Torokhov <dtor_core@ameritech.net>
Cc: linux-kernel@vger.kernel.org, Vojtech Pavlik <vojtech@suse.cz>,
Andrew Morton <akpm@osdl.org>
Subject: Re: [2.6 RFC/PATCH] Input: possible deadlock in i8042
Date: Sun, 30 Nov 2003 10:00:09 +0100 [thread overview]
Message-ID: <20031130090009.GA17038@ucw.cz> (raw)
In-Reply-To: <200311300303.57654.dtor_core@ameritech.net>
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.
> Dmitry
>
> ===================================================================
>
>
> ChangeSet@1.1512, 2003-11-30 02:42:54-05:00, dtor_core@ameritech.net
> Input: Use kseriod to register/unregister serio ports
>
>
> serio.c | 22 ++++++++++++++--------
> 1 files changed, 14 insertions(+), 8 deletions(-)
>
> ===================================================================
>
> diff -Nru a/drivers/input/serio/serio.c b/drivers/input/serio/serio.c
> --- a/drivers/input/serio/serio.c Sun Nov 30 03:01:40 2003
> +++ b/drivers/input/serio/serio.c Sun Nov 30 03:01:40 2003
> @@ -83,8 +83,10 @@
> }
> }
>
> -#define SERIO_RESCAN 1
> -#define SERIO_RECONNECT 2
> +#define SERIO_RESCAN 1
> +#define SERIO_RECONNECT 2
> +#define SERIO_REGISTER_PORT 3
> +#define SERIO_UNREGISTER_PORT 4
>
> static DECLARE_WAIT_QUEUE_HEAD(serio_wait);
> static DECLARE_COMPLETION(serio_exited);
> @@ -111,6 +113,14 @@
> goto event_done;
>
> switch (event->type) {
> + case SERIO_REGISTER_PORT :
> + __serio_register_port(event->serio);
> + break;
> +
> + case SERIO_UNREGISTER_PORT :
> + __serio_unregister_port(event->serio);
> + break;
> +
> case SERIO_RECONNECT :
> if (event->serio->dev && event->serio->dev->reconnect)
> if (event->serio->dev->reconnect(event->serio) == 0)
> @@ -192,9 +202,7 @@
>
> void serio_register_port(struct serio *serio)
> {
> - down(&serio_sem);
> - __serio_register_port(serio);
> - up(&serio_sem);
> + serio_queue_event(serio, SERIO_REGISTER_PORT);
> }
>
> /*
> @@ -210,9 +218,7 @@
>
> void serio_unregister_port(struct serio *serio)
> {
> - down(&serio_sem);
> - __serio_unregister_port(serio);
> - up(&serio_sem);
> + serio_queue_event(serio, SERIO_UNREGISTER_PORT);
> }
>
> /*
>
--
Vojtech Pavlik
SuSE Labs, SuSE CR
next prev parent reply other threads:[~2003-11-30 9:00 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-11-30 8:03 [2.6 RFC/PATCH] Input: possible deadlock in i8042 Dmitry Torokhov
2003-11-30 9:00 ` Vojtech Pavlik [this message]
2003-11-30 9:19 ` Dmitry Torokhov
2003-12-01 6:58 ` Dmitry Torokhov
2003-12-01 6:59 ` Dmitry Torokhov
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