On Sun, Aug 3, 2008 at 10:54 AM, Yinghai Lu <yhlu.kernel@gmail.com> wrote:
quoted text
>>>   * 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.
>

how about this one?

diff --git a/include/linux/irq.h b/include/linux/irq.h
index bd69d90..9d87f6a 100644
--- a/include/linux/irq.h
+++ b/include/linux/irq.h
@@ -154,6 +154,8 @@ struct irq_chip {
  * @name:              flow handler name for /proc/interrupts output
  */
 struct irq_desc {
+       unsigned int            irq;
+       struct irq_desc         *next;
        irq_flow_handler_t      handle_irq;
        struct irq_chip         *chip;
        struct msi_desc         *msi_desc;
@@ -181,7 +183,7 @@ struct irq_desc {
        const char              *name;
 } ____cacheline_internodealigned_in_smp;

-extern struct irq_desc irq_desc[NR_IRQS];
+extern struct irq_desc *get_irq_desc(unsigned int irq);

 /*
  * Migration helpers for obsolete names, they will go away:
diff --git a/kernel/irq/handle.c b/kernel/irq/handle.c
index e9d022c..347edb8 100644
--- a/kernel/irq/handle.c
+++ b/kernel/irq/handle.c
@@ -48,7 +48,90 @@ handle_bad_irq(unsigned int irq, struct irq_desc *desc)
  * Controller mappings for all interrupt sources:
  */
 int nr_irqs = NR_IRQS;
-struct irq_desc irq_desc[NR_IRQS] __cacheline_aligned_in_smp = {
+
+#ifdef CONFIG_HAVE_DYN_ARRAY
+static struct irq_desc irq_desc_init __initdata = {
+       .irq = -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
+#endif
+};
+
+static int nr_irq_desc = NR_VECTORS;
+
+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));
+
+       for (i = 1; i < *da->nr; i++)
+               desc[i-1].next = &desc[i];
+}
+
+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(unsigned int irq)
+{
+       struct irq_desc *desc, *desc_pri;
+
+       BUG_ON(irq == -1U);
+
+       desc = &irq_desc[0];
+       while (desc) {
+               if (desc->irq == irq)
+                       return desc;
+
+               if (desc->irq == -1U) {
+                       desc->irq = irq;
+                       return desc;
+               }
+               desc_pri = desc;
+               desc = desc->next;
+       }
+
+       /*
+        *  we run out of pre-allocate ones
+        *  and __alloc_bootmem or kzalloc could be used
+        */
+
+        if (after_bootmem)
+                desc = (struct irq_desc *) get_zeroed_page(GFP_ATOMIC);
+        else
+                desc = alloc_bootmem_pages(PAGE_SIZE);
+
+        if (!desc || ((unsigned long)desc & ~PAGE_MASK))
+               panic("please boot with nr_irq_desc= %d\n", nr_irq_desc * 2);
+
+       desc_pri->next = desc;
+       desc->irq = irq;
+
+       return desc;
+}
+
+#else
+
+static struct irq_desc irq_desc[NR_IRQS] __cacheline_aligned_in_smp = {
        [0 ... NR_IRQS-1] = {
                .status = IRQ_DISABLED,
                .chip = &no_irq_chip,
@@ -61,6 +144,16 @@ struct irq_desc irq_desc[NR_IRQS]
__cacheline_aligned_in_smp = {
        }
 };

+struct irq_desc *get_irq_desc(unsigned int irq)
+{
+       if (irq < nr_irqs)
+               return &irq_desc[irq];
+
+       return NULL;
+}
+
+#endif
+
 /*
  * What should we do if we get a hw irq event on an illegal vector?
  * Each architecture has to answer this themself.

do we need to lock to avoid racing in get_irq_desc?

YH
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