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>

3 files changed, 10 insertions, 18 deletions

diff --git a/arch/x86/kernel/io_apic_64.c b/arch/x86/kernel/io_apic_64.c
index 51ef7eb75f2e..708be9724daf 100644
--- a/arch/x86/kernel/io_apic_64.c
+++ b/arch/x86/kernel/io_apic_64.c
@@ -1871,10 +1871,10 @@ unmask:
 
 static void ir_irq_migration(struct work_struct *work)
 {
-        int irq;
+        unsigned int irq;
+        struct irq_desc *desc;
 
-        for (irq = 0; irq < nr_irqs; irq++) {
-                struct irq_desc *desc = irq_to_desc(irq);
+        for_each_irq_desc(irq, desc) {
                 if (desc->status & IRQ_MOVE_PENDING) {
                         unsigned long flags;
 
diff --git a/arch/x86/kernel/irq_64.c b/arch/x86/kernel/irq_64.c
index 4a0a4eb44dcb..b3cf55e325f5 100644
--- a/arch/x86/kernel/irq_64.c
+++ b/arch/x86/kernel/irq_64.c
@@ -224,17 +224,16 @@ void fixup_irqs(cpumask_t map)
 {
         unsigned int irq;
         static int warned;
+        struct irq_desc *desc;
 
-        for (irq = 0; irq < nr_irqs; irq++) {
+        for_each_irq_desc(irq, desc) {
                 cpumask_t mask;
                 int break_affinity = 0;
                 int set_affinity = 1;
-                struct irq_desc *desc;
 
                 if (irq == 2)
                         continue;
 
-                desc = irq_to_desc(irq);
                 /* interrupt's are disabled at this point */
                 spin_lock(&desc->lock);
 
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;
-                }
         }
 }