Fix possible race in destroy_and_reserve_irq()

Currently, destroy_and_reserve_irq() sets irq_status[irq] UNUSED using clear_irq_vector() and sets irq_status[irq] RSVD using reserve_irq(). But there is a race window because vector_lock is once released between them. This patch fixes this race window.

---
 arch/ia64/kernel/irq_ia64.c |   17 ++++++-----------
 1 files changed, 6 insertions(+), 11 deletions(-)

Index: linux-2.6.23-rc1/arch/ia64/kernel/irq_ia64.c =================================--- linux-2.6.23-rc1.orig/arch/ia64/kernel/irq_ia64.c +++ linux-2.6.23-rc1/arch/ia64/kernel/irq_ia64.c
@@ -101,15 +101,6 @@ int check_irq_used(int irq)
return -1;
}

-static void reserve_irq(unsigned int irq)
-{
- unsigned long flags;
-
- spin_lock_irqsave(&vector_lock, flags);
- irq_status[irq] = IRQ_RSVD;
- spin_unlock_irqrestore(&vector_lock, flags);
-}
-
static inline int find_unassigned_irq(void)
{
int irq;
@@ -302,10 +293,14 @@ static cpumask_t vector_allocation_domai

void destroy_and_reserve_irq(unsigned int irq)
{
+ unsigned long flags;
+
dynamic_irq_cleanup(irq);

- clear_irq_vector(irq);
- reserve_irq(irq);
+ spin_lock_irqsave(&vector_lock, flags);
+ __clear_irq_vector(irq);
+ irq_status[irq] = IRQ_RSVD;
+ spin_unlock_irqrestore(&vector_lock, flags);
}

static int __reassign_irq_vector(int irq, int cpu)