Re: [PATCH] irq: handle irq0 special only on x86

Re: [PATCH] irq: handle irq0 special only on x86

[Uwe Kleine-König]

Hello,

On Wed, Dec 09, 2009 at 10:20:01AM +0100, Uwe Kleine-König wrote:
> I just noticed this when digging in the irq handling.  At least for arm
> this doesn't make sense.  Not sure if x86 is the only arch this test
> is valid for, but probably it is.
... so I added linux-arch@vger.kernel.org
> 
> Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: H. Peter Anvin <hpa@zytor.com>
> ---
>  kernel/irq/spurious.c |    2 ++
>  1 files changed, 2 insertions(+), 0 deletions(-)
> 
> diff --git a/kernel/irq/spurious.c b/kernel/irq/spurious.c
> index 22b0a6e..4996b66 100644
> --- a/kernel/irq/spurious.c
> +++ b/kernel/irq/spurious.c
> @@ -199,8 +199,10 @@ try_misrouted_irq(unsigned int irq, struct irq_desc *desc,
>  	if (irqfixup < 2)
>  		return 0;
>  
> +#if defined(CONFIG_ARCH_X86)
>  	if (!irq)
>  		return 1;
> +#endif
>  
>  	/*
>  	 * Since we don't get the descriptor lock, "action" can
the feed-back I have got up to now wasn't helpfull.  (Only some "irq0 is
evil---no it's not" discussion.) So what do you think?  I admit the
#ifdef isn't nice, but if the semantic is OK I'm willing to rework it
into something more pretty.

Best regards
Uwe

-- 
Pengutronix e.K.                              | Uwe Kleine-König            |
Industrial Linux Solutions                    | http://www.pengutronix.de/  |

Re: [PATCH] irq: handle irq0 special only on x86

[H. Peter Anvin]

On 01/12/2010 07:59 AM, Uwe Kleine-König wrote:
> the feed-back I have got up to now wasn't helpfull.  (Only some "irq0 is
> evil---no it's not" discussion.) So what do you think?  I admit the
> #ifdef isn't nice, but if the semantic is OK I'm willing to rework it
> into something more pretty.

There was a debate on this a long time ago, and the outcome was that IRQ
0 is invalid, across the kernel, and that it is up to each architecture
to carry exceptions (like IRQ 0 for the timer interrupt in x86.)  Hinc
dictat Linus, so you would have to convince him before any of the arch
maintainer could realistically even consider this change.

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.