linux-kernel - Re: [PATCH V2] mips: irq: add stackoverflow detection

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Date:	Wed, 22 Sep 2010 11:07:01 +0100
From:	Ralf Baechle <ralf@...ux-mips.org>
To:	jiang.adam@...il.com
Cc:	dmitri.vorobiev@...ial.com, wuzhangjin@...il.com,
	ddaney@...iumnetworks.com, peterz@...radead.org,
	fweisbec@...il.com, tj@...nel.org, tglx@...utronix.de,
	mingo@...e.hu, linux-mips@...ux-mips.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2] mips: irq: add stackoverflow detection

On Fri, Aug 27, 2010 at 06:32:06PM +0900, jiang.adam@...il.com wrote:

> diff --git a/arch/mips/Kconfig.debug b/arch/mips/Kconfig.debug
> index 43dc279..f437cd1 100644
> --- a/arch/mips/Kconfig.debug
> +++ b/arch/mips/Kconfig.debug
> @@ -67,6 +67,15 @@ config CMDLINE_OVERRIDE
>  
>  	  Normally, you will choose 'N' here.
>  
> +config DEBUG_STACKOVERFLOW
> +	bool "Check for stack overflows"
> +	depends on DEBUG_KERNEL
> +	help
> +	  This option will cause messages to be printed if free stack space
> +	  drops below a certain limit(2GB on MIPS). The debugging option

I better upgrade my meory then.  2GB is a LOTS :)

> +	  provides another way to check stack overflow happened on kernel mode
> +	  stack usually caused by nested interruption.
> +
>  config DEBUG_STACK_USAGE
>  	bool "Enable stack utilization instrumentation"
>  	depends on DEBUG_KERNEL
> diff --git a/arch/mips/kernel/irq.c b/arch/mips/kernel/irq.c
> index c6345f5..d0b924d 100644
> --- a/arch/mips/kernel/irq.c
> +++ b/arch/mips/kernel/irq.c
> @@ -151,6 +151,26 @@ void __init init_IRQ(void)
>  #endif
>  }
>  
> +#ifdef DEBUG_STACKOVERFLOW
> +static inline void check_stack_overflow(void)
> +{
> +	long sp;

Addresses in Linux should always be unsigned long.

> +
> +	__asm__ __volatile__("move %0, $sp" : "=r" (sp));
> +	sp = sp & (THREAD_SIZE-1);

For THREAD_SIZE - 1 there is the symbol THREAD_MASK.

> +	/* check for stack overflow: is there less than 2KB free? */
> +	if (unlikely(sp < (sizeof(struct thread_info) + 2048))) {

Looks good otherwise, will queue.

  Ralf
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