irq: replace loop with nr_irqs with for_each_irq_desc

There are a handful of loops that go from 0 to nr_irqs and use
get_irq_desc() on them. These would allocate all the irq_desc
entries, regardless of the need for them.

Use the smarter for_each_irq_desc() iterator that will only iterate
over the present ones.

v2: make sure arch without GENERIC_HARDIRQS work too

Signed-off-by: Yinghai Lu <yhlu.kernel@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 5 insertions, 12 deletions

diff --git a/arch/x86/kernel/irqinit_64.c b/arch/x86/kernel/irqinit_64.c
index 0744b49b4d12..cd9f42d028d9 100644
--- a/arch/x86/kernel/irqinit_64.c
+++ b/arch/x86/kernel/irqinit_64.c
@@ -142,25 +142,18 @@ void __init init_ISA_irqs(void)
         init_bsp_APIC();
         init_8259A(0);
 
-        for (i = 0; i < nr_irqs; i++) {
+        for (i = 0; i < 16; i++) {
                 struct irq_desc *desc = irq_to_desc(i);
 
                 desc->status = IRQ_DISABLED;
                 desc->action = NULL;
                 desc->depth = 1;
 
-                if (i < 16) {
-                        /*
-                         * 16 old-style INTA-cycle interrupts:
-                         */
-                        set_irq_chip_and_handler_name(i, &i8259A_chip,
+                /*
+                 * 16 old-style INTA-cycle interrupts:
+                 */
+                set_irq_chip_and_handler_name(i, &i8259A_chip,
                                                       handle_level_irq, "XT");
-                } else {
-                        /*
-                         * 'high' PCI IRQs filled in on demand
-                         */
-                        desc->chip = &no_irq_chip;
-                }
         }
 }