linux-kernel - Re: [PATCH 00/25] dyn_array and nr

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Date:	Sun, 3 Aug 2008 10:54:28 -0700
From:	"Yinghai Lu" <yhlu.kernel@...il.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	"Alan Cox" <alan@...rguk.ukuu.org.uk>
Cc:	"Ingo Molnar" <mingo@...e.hu>,
	"Thomas Gleixner" <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	"Dhaval Giani" <dhaval@...ux.vnet.ibm.com>,
	"Mike Travis" <travis@....com>,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 00/25] dyn_array and nr_irqs support v3

On Sun, Aug 3, 2008 at 2:15 AM, Eric W. Biederman <ebiederm@...ssion.com> wrote:
> "Yinghai Lu" <yhlu.kernel@...il.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 ?

-1U

>
>> +       .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.

could use pre_allocate array + list to replace irq_desc array.

YH
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