linux-kernel - Re: [PATCH v2] ARM: exynos_defconfig: Enable CONFIG_LOCKUP

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Date:	Wed, 07 Jan 2015 15:23:20 +0100
From:	Krzysztof Kozlowski <k.kozlowski@...sung.com>
To:	Anand Moon <moon.linux@...oo.com>
Cc:	Russell King <linux@....linux.org.uk>,
	Kukjin Kim <kgene@...nel.org>,
	Javier Martinez Canillas <javier.martinez@...labora.co.uk>,
	Doug Anderson <dianders@...omium.org>,
	Kevin Hilman <khilman@...aro.org>,
	Sachin Kamat <sachin.kamat@...sung.com>,
	Sjoerd Simons <sjoerd.simons@...labora.co.uk>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Tushar Behera <tushar.behera@...aro.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-samsung-soc@...r.kernel.org" 
	<linux-samsung-soc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] ARM: exynos_defconfig: Enable CONFIG_LOCKUP_DETECTOR

On śro, 2015-01-07 at 13:56 +0000, Anand Moon wrote:
> Hi Kszysztof Kozlowski,
> 
> I picked up the bellow line from 
> 
> 
> Documentation/locking/lockdep-design.txt  line no 18
> 
> I understand that by enabling this flag we could detect possible 
> 
> deadlock situation with the kernel. Sorry for the noise.

...and lockdep-design.txt describes LOCKDEP. Not LOCKUP. So why you are
enabling lockup?

Best regards,
Krzysztof

> 
> 
> -Anand Moon
> 
> 
> 
> On Wednesday, January 7, 2015 6:57 PM, Krzysztof Kozlowski <k.kozlowski@...sung.com> wrote:
> On śro, 2015-01-07 at 18:29 +0530, Anand Moon wrote:
> > Enable CONFIG_LOCKUP_DETECTOR to validate kernel locks state for exynos SOC.
> > 
> > Enabling CONFIG_LOCKUP_DETECTOR help validator tracks the 'state' of lock-classes,
> > and it tracks dependencies between different lock-classes.
> > The validator maintains a rolling proof that the state and
> > the dependencies are correct.
> 
> Unfortunately this is not correct. Lockup detector does something else.
> Please read the help/manual for LOCKUP_DETECTOR. You can find in
> lib/Kconfig.debug (around line 667).
> 
> Best regards,
> Krzysztof
> 
> > 
> > Changes since v2:
> >  * Made commit message more clear
> >  * Corrected grammer in code comment
> > 
> > Tested on Exynos5422 ODROID XU3 board.
> > 
> > Signed-off-by: Anand Moon <moon.linux@...oo.com>
> > Reviewed-by: Krzysztof Kozlowski <k.kozlowski@...sung.com>
> > ---
> >  arch/arm/configs/exynos_defconfig | 1 +
> >  1 file changed, 1 insertion(+)
> > 
> > diff --git a/arch/arm/configs/exynos_defconfig b/arch/arm/configs/exynos_defconfig
> > index 5ef14de..ecd9987 100644
> > --- a/arch/arm/configs/exynos_defconfig
> > +++ b/arch/arm/configs/exynos_defconfig
> > @@ -178,6 +178,7 @@ CONFIG_PRINTK_TIME=y
> >  CONFIG_DEBUG_FS=y
> >  CONFIG_MAGIC_SYSRQ=y
> >  CONFIG_DEBUG_KERNEL=y
> > +CONFIG_LOCKUP_DETECTOR=y
> >  CONFIG_DETECT_HUNG_TASK=y
> >  CONFIG_DEBUG_RT_MUTEXES=y
> >  CONFIG_DEBUG_SPINLOCK=y

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