[Xen-devel] Re: [PATCH] xen: fix off-by-one error in find_unbound_irq

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

BTW, this is against xen/master, the original patch isn't in xen/next.

On Fri, 2010-02-26 at 10:59 +0000, Ian Campbell wrote:
> e459de95 "Find an unbound irq number in reverse order (high to low)" 
> introduced
> an off by one error which would cause repeated allocations of the nr_irq'th 
> IRQ
> if there are no spare interrupts (i.e. get_nr_hw_irqs() == nr_irqs).
> 
> Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
> Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> Cc: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>
> ---
>  drivers/xen/events.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/xen/events.c b/drivers/xen/events.c
> index 99f2b2a..5c64e1d 100644
> --- a/drivers/xen/events.c
> +++ b/drivers/xen/events.c
> @@ -377,7 +377,7 @@ static int find_unbound_irq(void)
>               if (irq_info[irq].type == IRQT_UNBOUND)
>                       break;
>  
> -     if (irq == start || irq == nr_irqs)
> +     if (irq == start || irq == nr_irqs - 1)
>               panic("No available IRQ to bind to: increase nr_irqs!\n");
>  
>       desc = irq_to_desc_alloc_node(irq, 0);



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