Subject: Re: [PATCH v3 3/3] sched: BUG when stack end location is over written

From: Michael Ellerman <[email-masked]>
Date: Fri, 12 Sep 2014 14:06:57 +1000

On Thu, 2014-09-11 at 16:41 +0100, Aaron Tomlin wrote:
> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index a285900..2a8280a 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -824,6 +824,18 @@ config SCHEDSTATS
>  	  application, you can say N to avoid the very slight overhead
>  	  this adds.
>  
> +config SCHED_STACK_END_CHECK
> +	bool "Detect stack corruption on calls to schedule()"
> +	depends on DEBUG_KERNEL
> +	default y

Did you really mean default y?

Doing so means it will be turned on more or less everywhere, which defeats the
purpose of having a config option in the first place.

> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index ec1a286..0b70b73 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -2660,6 +2660,9 @@ static noinline void __schedule_bug(struct task_struct *prev)
>   */
>  static inline void schedule_debug(struct task_struct *prev)
>  {
> +#ifdef CONFIG_SCHED_STACK_END_CHECK
> +	BUG_ON(unlikely(task_stack_end_corrupted(prev)))
> +#endif

If this was my code I'd make you put that in a static inline.

cheers