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>

7 files changed, 25 insertions, 26 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;
-                }
         }
 }
 
diff --git a/include/linux/irq.h b/include/linux/irq.h
index c9ffef7c3b44..9de16ca8b8e5 100644
--- a/include/linux/irq.h
+++ b/include/linux/irq.h
@@ -202,9 +202,16 @@ extern struct irq_desc irq_desc[NR_IRQS];
 extern struct irq_desc *irq_desc;
 #endif
 
+#ifdef CONFIG_GENERIC_HARDIRQS
+#define for_each_irq_desc(irq, desc)            \
+        for (irq = 0, desc = irq_desc; irq < nr_irqs; irq++, desc = &irq_desc[irq])
+#endif
+
 #else
 
 extern struct irq_desc *sparse_irqs;
+#define for_each_irq_desc(irqX, desc)           \
+        for (desc = sparse_irqs, irqX = desc->irq; desc && irqX != -1U; desc = desc->next, irqX = desc ? desc->irq : -1U)
 
 #endif
 
diff --git a/kernel/irq/internals.h b/kernel/irq/internals.h
index 422dd00c8bd3..c9767e641980 100644
--- a/kernel/irq/internals.h
+++ b/kernel/irq/internals.h
@@ -14,11 +14,11 @@ extern int __irq_set_trigger(struct irq_desc *desc, unsigned int irq,
                 unsigned long flags);
 
 #ifdef CONFIG_PROC_FS
-extern void register_irq_proc(unsigned int irq);
+extern void register_irq_proc(unsigned int irq, struct irq_desc *desc);
 extern void register_handler_proc(unsigned int irq, struct irqaction *action);
 extern void unregister_handler_proc(unsigned int irq, struct irqaction *action);
 #else
-static inline void register_irq_proc(unsigned int irq) { }
+static inline void register_irq_proc(unsigned int irq, struct irq_desc *desc) { }
 static inline void register_handler_proc(unsigned int irq,
                                          struct irqaction *action) { }
 static inline void unregister_handler_proc(unsigned int irq,
diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index b5943e9f95aa..5070f55fdc16 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -478,7 +478,7 @@ int setup_irq(unsigned int irq, struct irqaction *new)
         spin_unlock_irqrestore(&desc->lock, flags);
 
         new->irq = irq;
-        register_irq_proc(irq);
+        register_irq_proc(irq, desc);
         new->dir = NULL;
         register_handler_proc(irq, new);
 
diff --git a/kernel/irq/proc.c b/kernel/irq/proc.c
index c2f356c808f6..bc0993d86c8b 100644
--- a/kernel/irq/proc.c
+++ b/kernel/irq/proc.c
@@ -182,11 +182,10 @@ void register_handler_proc(unsigned int irq, struct irqaction *action)
 
 #define MAX_NAMELEN 10
 
-void register_irq_proc(unsigned int irq)
+void register_irq_proc(unsigned int irq, struct irq_desc *desc)
 {
         char name [MAX_NAMELEN];
         struct proc_dir_entry *entry;
-        struct irq_desc *desc = irq_to_desc(irq);
 
         if (!root_irq_dir || (desc->chip == &no_irq_chip) || desc->dir)
                 return;
@@ -230,7 +229,8 @@ void register_default_affinity_proc(void)
 
 void init_irq_proc(void)
 {
-        int i;
+        unsigned int irq;
+        struct irq_desc *desc;
 
         /* create /proc/irq */
         root_irq_dir = proc_mkdir("irq", NULL);
@@ -242,7 +242,7 @@ void init_irq_proc(void)
         /*
          * Create entries for all existing IRQs.
          */
-        for (i = 0; i < nr_irqs; i++)
-                register_irq_proc(i);
+        for_each_irq_desc(irq, desc)
+                register_irq_proc(irq, desc);
 }