linux-kernel - Re: [PATCH] Limit irq nesting

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Message-Id: <20080717105532.157E.KOSAKI.MOTOHIRO@jp.fujitsu.com>
Date:	Thu, 17 Jul 2008 10:57:56 +0900
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	Mikulas Patocka <mpatocka@...hat.com>
Cc:	kosaki.motohiro@...fujitsu.com, torvalds@...ux-foundation.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Limit irq nesting

Hi Mikulas,

> ---
>  include/linux/interrupt.h |    7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> Index: linux-2.6.26-rc8/include/linux/interrupt.h
> ===================================================================
> --- linux-2.6.26-rc8.orig/include/linux/interrupt.h	2008-06-25 03:58:20.000000000 +0200
> +++ linux-2.6.26-rc8/include/linux/interrupt.h	2008-07-01 17:42:44.000000000 +0200
> @@ -16,6 +16,11 @@
>  #include <asm/system.h>
>  
>  /*
> + * Max number of interrupt handlers on a stack. To prevent stack overflow.
> + */
> +#define MAX_NESTED_INTERRUPTS	2
> +
> +/*
>   * These correspond to the IORESOURCE_IRQ_* defines in
>   * linux/ioport.h to select the interrupt line behaviour.  When
>   * requesting an interrupt without specifying a IRQF_TRIGGER, the

I have no objection to your approach.
but I don't know MAX_NESTED_INTERRUPTS is properly or not.

Could you explain why MAX_NESTED_INTERRUPTS is two?
Is it architecture independent properly number?



> @@ -95,7 +100,7 @@ extern void devm_free_irq(struct device 
>  #ifdef CONFIG_LOCKDEP
>  # define local_irq_enable_in_hardirq()	do { } while (0)
>  #else
> -# define local_irq_enable_in_hardirq()	local_irq_enable()
> +# define local_irq_enable_in_hardirq()	do { if (hardirq_count() < (MAX_NESTED_INTERRUPTS << HARDIRQ_SHIFT)) local_irq_enable(); } while (0)
>  #endif
>  
>  extern void disable_irq_nosync(unsigned int irq);


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