linux-kernel - Re: [PATCH] atkbd: cleanup only once

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Message-Id: <200706280118.36052.dtor@insightbb.com>
Date:	Thu, 28 Jun 2007 01:18:35 -0400
From:	Dmitry Torokhov <dtor@...ightbb.com>
To:	dave young <hidave.darkstar@...il.com>
Cc:	Greg KH <gregkh@...e.de>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] atkbd: cleanup only once

On Wednesday 27 June 2007 01:02, dave young wrote:
> 2007/6/27, Dmitry Torokhov <dtor@...ightbb.com>:
> > On Wednesday 27 June 2007 00:28, Greg KH wrote:
> > > On Wed, Jun 27, 2007 at 12:34:09AM -0400, Dmitry Torokhov wrote:
> > > > Hi Dave,
> > > >
> > > > On Wednesday 27 June 2007 06:59, Dave Young wrote:
> > > > > Hi,
> > > > >
> > > > > If you press ctrl+alt+del several times as kernel booting (before user level bootin), the kernel will oops. I found the ps2_command is called more than once, then the ps2dev->serio maybe NULL pointer.
> > > > >
> > > > > 2.6.22-rc5 and 2.6.22-rc6 have same result.
> > > > >
> > > > > Signed-off-by: Dave Young <hidave.darkstar@...il.com>
> > > > > ---
> > > > > diff -upr linux/drivers/input/keyboard/atkbd.c linux.new/drivers/input/keyboard/atkbd.c
> > > > > --- linux/drivers/input/keyboard/atkbd.c  2007-06-27 10:38:37.000000000 +0000
> > > > > +++ linux.new/drivers/input/keyboard/atkbd.c      2007-06-27 10:37:39.000000000 +0000
> > > > > @@ -795,6 +795,11 @@ static int atkbd_activate(struct atkbd *
> > > > >
> > > > >  static void atkbd_cleanup(struct serio *serio)
> > > > >  {
> > > > > + static int flag;
> > > > > +
> > > > > + if(flag)
> > > > > +         return;
> > > > > + flag = 1;
> > > >
> > > > Unfortunately this will prevent atkbd from resetting keyboard on 2nd
> > > > suspend attempt. It will also not work if you have an active MUX and
> > > > have a couple of keyboards connected.
> > > >
> > > > Greg, now that you removed rwsem from subsystem (and subsystem itself
> > > > for that matter) there is nothing as far as I can see that stops
> > > > several threads from running device_shutdown() simultaneously. I also
> > > > do not see what would isolate device probing and shutting them down
> > > > at the same time. Am I missing something?
> > >
> > > There was never anything stopping that from happening before.  No driver
> > > core code was using that rwsem, so it wasn't protecting anything,
> > > despite people trying to use it as if it was :)
> > >
> >
> > It did protect device_shutdown() from itself, didn't it?
> >
> > --
> > Dmitry
> >
> how about check ps2dev->serio in ps2_command before use it?

I don't think we ever set it to NULL. Does the patch below help any?

-- 
Dmitry


Signed-off-by: Dmitry Torokhov <dtor@...l.ru>
---

 drivers/input/serio/serio.c |    2 ++
 1 files changed, 2 insertions(+)

Index: work/drivers/input/serio/serio.c
===================================================================
--- work.orig/drivers/input/serio/serio.c
+++ work/drivers/input/serio/serio.c
@@ -769,8 +769,10 @@ static int serio_driver_remove(struct de
 
 static void serio_cleanup(struct serio *serio)
 {
+	mutex_lock(&serio->drv_mutex);
 	if (serio->drv && serio->drv->cleanup)
 		serio->drv->cleanup(serio);
+	mutex_unlock(&serio->drv_mutex);
 }
 
 static void serio_shutdown(struct device *dev)
-
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