[PATCH] ARM: OMAPFB: panel-sony-acx565akm: fix bad unlock balance

[PATCH] ARM: OMAPFB: panel-sony-acx565akm: fix bad unlock balance

[Aaro Koskinen]

When booting Nokia N900 smartphone with v3.12 + omap2plus_defconfig
(LOCKDEP enabled) and CONFIG_DISPLAY_PANEL_SONY_ACX565AKM enabled,
the following BUG is seen during the boot:

[    7.302154] =====================================
[    7.307128] [ BUG: bad unlock balance detected! ]
[    7.312103] 3.12.0-los.git-2093492-00120-g5e01dc7 #3 Not tainted
[    7.318450] -------------------------------------
[    7.323425] kworker/u2:1/12 is trying to release lock (&ddata->mutex) at:
[    7.330657] [<c031b760>] acx565akm_enable+0x12c/0x18c
[    7.335998] but there are no more locks to release!

Fix by removing the extra mutex_unlock().

Reported-by: Eduardo Valentin <eduardo.valentin@ti.com>
Signed-off-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Cc: stable@vger.kernel.org
---
 drivers/video/omap2/displays-new/panel-sony-acx565akm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/video/omap2/displays-new/panel-sony-acx565akm.c b/drivers/video/omap2/displays-new/panel-sony-acx565akm.c
index e6d56f7..72fe2a8 100644
--- a/drivers/video/omap2/displays-new/panel-sony-acx565akm.c
+++ b/drivers/video/omap2/displays-new/panel-sony-acx565akm.c
@@ -616,7 +616,7 @@ static int acx565akm_enable(struct omap_dss_device *dssdev)
 
 	mutex_lock(&ddata->mutex);
 	r = acx565akm_panel_power_on(dssdev);
-	mutex_unlock(&ddata->mutex);
+	/* NOTE: acx565akm_panel_power_on() will unlock the mutex. */
 
 	if (r)
 		return r;
-- 
1.8.4.2

Re: [PATCH] ARM: OMAPFB: panel-sony-acx565akm: fix bad unlock balance

[Tomi Valkeinen]

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On 2013-11-06 23:24, Aaro Koskinen wrote:
> When booting Nokia N900 smartphone with v3.12 + omap2plus_defconfig
> (LOCKDEP enabled) and CONFIG_DISPLAY_PANEL_SONY_ACX565AKM enabled,
> the following BUG is seen during the boot:
> 
> [    7.302154] =====================================
> [    7.307128] [ BUG: bad unlock balance detected! ]
> [    7.312103] 3.12.0-los.git-2093492-00120-g5e01dc7 #3 Not tainted
> [    7.318450] -------------------------------------
> [    7.323425] kworker/u2:1/12 is trying to release lock (&ddata->mutex) at:
> [    7.330657] [<c031b760>] acx565akm_enable+0x12c/0x18c
> [    7.335998] but there are no more locks to release!
> 
> Fix by removing the extra mutex_unlock().
> 
> Reported-by: Eduardo Valentin <eduardo.valentin@ti.com>
> Signed-off-by: Aaro Koskinen <aaro.koskinen@iki.fi>
> Cc: stable@vger.kernel.org
> ---
>  drivers/video/omap2/displays-new/panel-sony-acx565akm.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/video/omap2/displays-new/panel-sony-acx565akm.c b/drivers/video/omap2/displays-new/panel-sony-acx565akm.c
> index e6d56f7..72fe2a8 100644
> --- a/drivers/video/omap2/displays-new/panel-sony-acx565akm.c
> +++ b/drivers/video/omap2/displays-new/panel-sony-acx565akm.c
> @@ -616,7 +616,7 @@ static int acx565akm_enable(struct omap_dss_device *dssdev)
>  
>  	mutex_lock(&ddata->mutex);
>  	r = acx565akm_panel_power_on(dssdev);
> -	mutex_unlock(&ddata->mutex);
> +	/* NOTE: acx565akm_panel_power_on() will unlock the mutex. */
>  
>  	if (r)
>  		return r;
> 

Hm why would you fix it like this? Why not remove the mutex_unlock from
acx565akm_panel_power_on()? Looks to me like that one is the buggy one.

 Tomi



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Re: [PATCH] ARM: OMAPFB: panel-sony-acx565akm: fix bad unlock balance

[Aaro Koskinen]

Hi,

On Mon, Nov 11, 2013 at 03:37:37PM +0200, Tomi Valkeinen wrote:
> On 2013-11-06 23:24, Aaro Koskinen wrote:
> > When booting Nokia N900 smartphone with v3.12 + omap2plus_defconfig
> > (LOCKDEP enabled) and CONFIG_DISPLAY_PANEL_SONY_ACX565AKM enabled,
> > the following BUG is seen during the boot:
> > 
> > [    7.302154] =====================================
> > [    7.307128] [ BUG: bad unlock balance detected! ]
> > [    7.312103] 3.12.0-los.git-2093492-00120-g5e01dc7 #3 Not tainted
> > [    7.318450] -------------------------------------
> > [    7.323425] kworker/u2:1/12 is trying to release lock (&ddata->mutex) at:
> > [    7.330657] [<c031b760>] acx565akm_enable+0x12c/0x18c
> > [    7.335998] but there are no more locks to release!
> > 
> > Fix by removing the extra mutex_unlock().
> > 
> > Reported-by: Eduardo Valentin <eduardo.valentin@ti.com>
> > Signed-off-by: Aaro Koskinen <aaro.koskinen@iki.fi>
> > Cc: stable@vger.kernel.org
> > ---
> >  drivers/video/omap2/displays-new/panel-sony-acx565akm.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/video/omap2/displays-new/panel-sony-acx565akm.c b/drivers/video/omap2/displays-new/panel-sony-acx565akm.c
> > index e6d56f7..72fe2a8 100644
> > --- a/drivers/video/omap2/displays-new/panel-sony-acx565akm.c
> > +++ b/drivers/video/omap2/displays-new/panel-sony-acx565akm.c
> > @@ -616,7 +616,7 @@ static int acx565akm_enable(struct omap_dss_device *dssdev)
> >  
> >  	mutex_lock(&ddata->mutex);
> >  	r = acx565akm_panel_power_on(dssdev);
> > -	mutex_unlock(&ddata->mutex);
> > +	/* NOTE: acx565akm_panel_power_on() will unlock the mutex. */
> >  
> >  	if (r)
> >  		return r;
> > 
> 
> Hm why would you fix it like this? Why not remove the mutex_unlock from
> acx565akm_panel_power_on()? Looks to me like that one is the buggy one.

The unlock needs to be there because acx565akm_bl_update_status()
also locks the mutex. I'll send a new version where the mutex_lock()
is done inside acx565akm_panel_power_on().

A.