Re: [PATCH v1] x86/irq: handle chained interrupts during IRQ migration

[Paul Mundt <lethal@linux-sh.org>]

On Tue, May 29, 2012 at 07:10:08PM +0530, Sundar Iyer wrote:
> diff --git a/include/linux/irqdesc.h b/include/linux/irqdesc.h
> index 2d921b3..7880722 100644
> --- a/include/linux/irqdesc.h
> +++ b/include/linux/irqdesc.h
> @@ -120,6 +120,16 @@ static inline int irq_has_action(unsigned int irq)
>  	return desc->action != NULL;
>  }
>  
> +/*
> + * Test to see if the IRQ is chained; it would not be requested and hence
> + * _IRQ_NOREQUEST would be set
> + */
> +static inline int irq_is_chained(unsigned int irq)
> +{
> +	struct irq_desc *desc = irq_to_desc(irq);
> +	return !(desc->status_use_accessors & IRQ_NOREQUEST);
> +}
> +

This approach looks highly suspect. There are many non-chained cases that
are also NOREQUEST. Chained IRQs are at the very least NOREQUEST,
NOPROBE, and NOTHREAD. You could test a mask of those and at least have a
vague change of not catching other unrelated IRQs. It would still be a
hack though, given that none of those status flags in and of themselves
require an IRQ to be chained.