linux-kernel - Re: [PATCH] backlight: grab ops

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Message-ID: <20101122100532.GA4693@pengutronix.de>
Date:	Mon, 22 Nov 2010 11:05:32 +0100
From:	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>
To:	Richard Purdie <rpurdie@...ux.intel.com>
Cc:	akpm <akpm@...ux-foundation.org>, linux-kernel@...r.kernel.org,
	kernel@...gutronix.de, stable@...nel.org
Subject: Re: [PATCH] backlight: grab ops_lock before testing bd->ops

Hello,

On Mon, Nov 22, 2010 at 09:59:07AM +0000, Richard Purdie wrote:
> On Mon, 2010-11-22 at 10:43 +0100, Uwe Kleine-König wrote:
> > According to the comment describing ops_lock in the definition of
> > struct backlight_device and when comparing with other functions in
> > backlight.c the mutex must be hold when checking ops to be non-NULL.
> > 
> > Signed-off-by: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
> 
> Acked-by: Richard Purdie <rpurdie@...ux.intel.com>
The problem was introduced by c835ee7f4154992e6cf0674d7ee136f5d36247a4
(that is in 2.6.29-rc1).  Is this relevant for stable?

Best regards
Uwe
 
> > ---
> >  drivers/video/backlight/backlight.c |   12 ++++++------
> >  1 files changed, 6 insertions(+), 6 deletions(-)
> > 
> > diff --git a/drivers/video/backlight/backlight.c b/drivers/video/backlight/backlight.c
> > index e207810..0870329 100644
> > --- a/drivers/video/backlight/backlight.c
> > +++ b/drivers/video/backlight/backlight.c
> > @@ -197,12 +197,12 @@ static int backlight_suspend(struct device *dev, pm_message_t state)
> >  {
> >  	struct backlight_device *bd = to_backlight_device(dev);
> >  
> > -	if (bd->ops->options & BL_CORE_SUSPENDRESUME) {
> > -		mutex_lock(&bd->ops_lock);
> > +	mutex_lock(&bd->ops_lock);
> > +	if (bd->ops && bd->ops->options & BL_CORE_SUSPENDRESUME) {
> >  		bd->props.state |= BL_CORE_SUSPENDED;
> >  		backlight_update_status(bd);
> > -		mutex_unlock(&bd->ops_lock);
> >  	}
> > +	mutex_unlock(&bd->ops_lock);
> >  
> >  	return 0;
> >  }
> > @@ -211,12 +211,12 @@ static int backlight_resume(struct device *dev)
> >  {
> >  	struct backlight_device *bd = to_backlight_device(dev);
> >  
> > -	if (bd->ops->options & BL_CORE_SUSPENDRESUME) {
> > -		mutex_lock(&bd->ops_lock);
> > +	mutex_lock(&bd->ops_lock);
> > +	if (bd->ops && bd->ops->options & BL_CORE_SUSPENDRESUME) {
> >  		bd->props.state &= ~BL_CORE_SUSPENDED;
> >  		backlight_update_status(bd);
> > -		mutex_unlock(&bd->ops_lock);
> >  	}
> > +	mutex_unlock(&bd->ops_lock);
> >  
> >  	return 0;
> >  }
> 
> 
> 

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |
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