Re: [Xen-devel] [PATCH RFC] suggestion on the inflight irq order

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Fri, 2013-06-14 at 20:07 +0900, Jaeyong Yoo wrote:
> Since inflight irq is only used for keeping track of on-going irqs, 
> I don't think it should be sorted by priority. (Only used for cleaing 
> all inflight irqs and debug-print all inflight irqs) For IRQ processing 
> at xen, we can save some time by not keeping it in order.

It does seem to be the case that only the lr_pending list needs to be
ordered, but I've always had trouble following the flow of interrupts
through these lists so I'll have to defer to Stefano on this one.

> Signed-off-by: Jaeyong Yoo <jaeyong.yoo@xxxxxxxxxxx>
> ---
>  xen/arch/arm/vgic.c |   11 +----------
>  1 file changed, 1 insertion(+), 10 deletions(-)
> 
> diff --git a/xen/arch/arm/vgic.c b/xen/arch/arm/vgic.c
> index 7eaccb7..47cc2a0 100644
> --- a/xen/arch/arm/vgic.c
> +++ b/xen/arch/arm/vgic.c
> @@ -666,7 +666,7 @@ void vgic_vcpu_inject_irq(struct vcpu *v, unsigned int 
> irq, int virtual)
>      int idx = irq >> 2, byte = irq & 0x3;
>      uint8_t priority;
>      struct vgic_irq_rank *rank = vgic_irq_rank(v, 8, idx);
> -    struct pending_irq *iter, *n = irq_to_pending(v, irq);
> +    struct pending_irq *n = irq_to_pending(v, irq);
>      unsigned long flags;
>      bool_t running;
>  
> @@ -692,16 +692,7 @@ void vgic_vcpu_inject_irq(struct vcpu *v, unsigned int 
> irq, int virtual)
>      if ( rank->ienable & (1 << (irq % 32)) )
>          gic_set_guest_irq(v, irq, GICH_LR_PENDING, priority);
>  
> -    list_for_each_entry ( iter, &v->arch.vgic.inflight_irqs, inflight )
> -    {
> -        if ( iter->priority > priority )
> -        {
> -            list_add_tail(&n->inflight, &iter->inflight);
> -            goto out;
> -        }
> -    }
>      list_add_tail(&n->inflight, &v->arch.vgic.inflight_irqs);
> -out:
>      spin_unlock_irqrestore(&v->arch.vgic.lock, flags);
>      /* we have a new higher priority irq, inject it into the guest */
>      running = v->is_running;



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