From: ebiederm@xmission.com (Eric W. Biederman)
To: "Yinghai Lu" <yhlu.kernel@gmail.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>, "Ingo Molnar" <mingo@elte.hu>,
       "Thomas Gleixner" <tglx@linutronix.de>,
       "H. Peter Anvin" <hpa@zytor.com>,
       "Dhaval Giani" <dhaval@linux.vnet.ibm.com>,
       "Mike Travis" <travis@sgi.com>,
       "Andrew Morton" <akpm@linux-foundation.org>,
       linux-kernel@vger.kernel.org
References: <1217732365-16595-1-git-send-email-yhlu.kernel@gmail.com>
	<m1fxpm8x3n.fsf@frodo.ebiederm.org>
	<86802c440808022304g41749d9dn7688c81c3fdbed8a@mail.gmail.com>
	<m18wve7gbt.fsf@frodo.ebiederm.org>
	<86802c440808030125v32c6a83aoe3c09eea6a6cce08@mail.gmail.com>
Date: Sun, 03 Aug 2008 02:15:54 -0700
In-Reply-To: <86802c440808030125v32c6a83aoe3c09eea6a6cce08@mail.gmail.com>
	(Yinghai Lu's message of "Sun, 3 Aug 2008 01:25:09 -0700")
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Subject: Re: [PATCH 00/25] dyn_array and nr_irqs support v3
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"Yinghai Lu" <yhlu.kernel@gmail.com> writes:

> how about
>
> diff --git a/kernel/irq/handle.c b/kernel/irq/handle.c
> index f4c8a03..aa6888c 100644
> --- a/kernel/irq/handle.c
> +++ b/kernel/irq/handle.c
> @@ -47,19 +47,73 @@ handle_bad_irq(unsigned int irq, struct irq_desc *desc)
>   *
>   * Controller mappings for all interrupt sources:
>   */
> -struct irq_desc irq_desc[NR_IRQS] __cacheline_aligned_in_smp = {
> -       [0 ... NR_IRQS-1] = {
> -               .status = IRQ_DISABLED,
> -               .chip = &no_irq_chip,
> -               .handle_irq = handle_bad_irq,
> -               .depth = 1,
> -               .lock = __SPIN_LOCK_UNLOCKED(irq_desc->lock),
> +static irq_desc **irq_desc_ptr;
> +DEFINE_DYN_ARRAY(irq_desc_ptr, sizeof(struct irq_desc *), nr_irqs,
> PAGE_SIZE, NULL);
> +
> +#define NR_IRQ_DESC    4096
> +
> +static struct irq_desc irq_desc__init = {
> +       .irq = -1;

Do you perhaps mean 0xffffffffU ?

> +       .status = IRQ_DISABLED,
> +       .chip = &no_irq_chip,
> +       .handle_irq = handle_bad_irq,
> +       .depth = 1,
> +       .lock = __SPIN_LOCK_UNLOCKED(irq_desc->lock),
>  #ifdef CONFIG_SMP
> -               .affinity = CPU_MASK_ALL
> +       .affinity = CPU_MASK_ALL
>  #endif
> -       }
>  };
>
> +static int nr_irq_desc = NR_IRQ_DESC;
> +
> +static int __init parse_nr_irq_desc(char *arg)
> +{
> +        if (arg)
> +                nr_irq_desc = simple_strtoul(arg, NULL, 0);
> +        return 0;
> +}
> +
> +early_param("nr_irq_desc", parse_nr_irq_desc);
> +
> +static void __init init_work(void *data)
> +{
> +       struct dyn_array *da = data;
> +       int i;
> +       struct  irq_desc *desc;
> +
> +       desc = *da->name;
> +
> +       for (i = 0; i < *da->nr; i++)
> +               memcpy(&desc[i], &irq_desc_init, sizeof(struct irq_desc));
> +}
> +
> +static struct irq_desc *irq_desc;
> +DEFINE_DYN_ARRAY(irq_desc, sizeof(struct irq_desc), nr_irq_desc,
> PAGE_SIZE, init_work);
> +
> +struct irq_desc *get_irq_desc(int irq)

Ugh.  This has the wrong type.  It must be unsigned int irq.
> +{
> +       struct irq_desc *desc;
> +       int i;
> +
> +       desc = irq_desc_ptr[irq];
> +
> +       if (desc)
> +               return desc;
> +
> +       for (i = 0; i < nr_irq_desc; i++) {
> +               if (irq_desc[i]->irq != -1)

Which makes this line wrong.
> +                       continue;
> +
> +               desc = &irq_desc[i];
> +               desc->irq = irq;
> +               irq_desc_ptr[irq] = desc;
> +
> +               return desc;
> +       }
> +
> +       panic("please boot with nr_irq_desc=%d\n", nr_irq_desc * 2);
> +}
> +
>  /*
>   * What should we do if we get a hw irq event on an illegal vector?
>   * Each architecture has to answer this themself.
>
>
> and later use get_irq_desc(i) instead irq_desc + i;

That is the general idea.

Eric

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