linux-kernel - Re: [PATCH] lib/Kconfig: make PREEMPT_COUNT depend on PREEMPT in DEBUG_ATOMIC

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Date:	Sat, 13 Feb 2016 13:11:37 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Yang Shi <yang.shi@...aro.org>
Cc:	mingo@...hat.com, linux-kernel@...r.kernel.org,
	linaro-kernel@...ts.linaro.org
Subject: Re: [PATCH] lib/Kconfig: make PREEMPT_COUNT depend on PREEMPT in
 DEBUG_ATOMIC_SLEEP

On Fri, Feb 12, 2016 at 10:14:22AM -0800, Yang Shi wrote:
> When building non-preempt kernel (PREEMPT_NONE), PREEMPT_COUNT is still enabled
> if DEBUG_ATOMIC_SLEEP is enabled. But, it sounds not make sense to have
> PREEMPT_COUNT set in non-preempt kernel.
> 
> So, make PREEMPT_COUNT depend on PREEMPT here.
> 
> Signed-off-by: Yang Shi <yang.shi@...aro.org>
> ---
>  lib/Kconfig.debug | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index ecb9e75..a5b6e11 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -1075,7 +1075,7 @@ config DEBUG_LOCKDEP
>  
>  config DEBUG_ATOMIC_SLEEP
>  	bool "Sleep inside atomic section checking"
> -	select PREEMPT_COUNT
> +	select PREEMPT_COUNT if PREEMPT

OK, so do tell, how is it supposed to debug atomic sections without
actually tracking atomic sections?