[PATCH] irq: clear kstat_irqs

[Yinghai Lu <yinghai@kernel.org>]

Impact: get correct kstat_irqs for msi etc

need to call clear_kstat_irqs(), so when reuse that irq_desc, could get correct
kstat in /proc/interrupts

also could make /proc/interrupts don't have none-<NULL> entries

don't need to worry about arch that doesn't support genirq, because they
will not call dynamic_irq_cleanup().

Signed-off-by: Yinghai Lu <yinghai@kernel.org>

---
 kernel/irq/chip.c      |    1 +
 kernel/irq/handle.c    |   11 +++++++++++
 kernel/irq/internals.h |    1 +
 3 files changed, 13 insertions(+)

Index: linux-2.6/kernel/irq/chip.c
===================================================================
--- linux-2.6.orig/kernel/irq/chip.c
+++ linux-2.6/kernel/irq/chip.c
@@ -81,6 +81,7 @@ void dynamic_irq_cleanup(unsigned int ir
 	desc->handle_irq = handle_bad_irq;
 	desc->chip = &no_irq_chip;
 	desc->name = NULL;
+	clear_kstat_irqs(desc);
 	spin_unlock_irqrestore(&desc->lock, flags);
 }
 
Index: linux-2.6/kernel/irq/handle.c
===================================================================
--- linux-2.6.orig/kernel/irq/handle.c
+++ linux-2.6/kernel/irq/handle.c
@@ -270,6 +270,17 @@ struct irq_desc *irq_to_desc_alloc_cpu(u
 }
 #endif /* !CONFIG_SPARSE_IRQ */
 
+void clear_kstat_irqs(struct irq_desc *desc)
+{
+	unsigned long bytes;
+	char *ptr;
+
+	ptr = (char *)desc->kstat_irqs;
+	/* Compute how many bytes we need to clear */
+	bytes = nr_cpu_ids * sizeof(unsigned int);
+	memset(ptr, 0, bytes);
+}
+
 /*
  * What should we do if we get a hw irq event on an illegal vector?
  * Each architecture has to answer this themself.
Index: linux-2.6/kernel/irq/internals.h
===================================================================
--- linux-2.6.orig/kernel/irq/internals.h
+++ linux-2.6/kernel/irq/internals.h
@@ -15,6 +15,7 @@ extern int __irq_set_trigger(struct irq_
 
 extern struct lock_class_key irq_desc_lock_class;
 extern void init_kstat_irqs(struct irq_desc *desc, int cpu, int nr);
+extern void clear_kstat_irqs(struct irq_desc *desc);
 extern spinlock_t sparse_irq_lock;
 
 #ifdef CONFIG_SPARSE_IRQ