Re: [PATCH v2] ARM: exynos_defconfig: Enable CONFIG_LOCKUP_DETECTOR

Re: [PATCH v2] ARM: exynos_defconfig: Enable CONFIG_LOCKUP_DETECTOR

[Krzysztof Kozlowski]

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@yahoo.com>
> Reviewed-by: Krzysztof Kozlowski <k.kozlowski@samsung.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

Re: [PATCH v2] ARM: exynos_defconfig: Enable CONFIG_LOCKUP_DETECTOR

[Krzysztof Kozlowski]

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@samsung.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@yahoo.com>
> > Reviewed-by: Krzysztof Kozlowski <k.kozlowski@samsung.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