genirq: do not execute DEBUG_SHIRQ when irq setup failed

When requesting an IRQ, the DEBUG_SHIRQ code executes a fake IRQ just to make
sure the driver is ready to receive an IRQ immediately.  The problem was that
this fake IRQ was being executed even if interrupt line failed to be allocated
by __setup_irq.
Signed-off-by: NLuis Henriques <henrix@sapo.pt>
LKML-Reference: <20090401170635.GA4392@hades.domain.com>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
[ fixed bug pointed out by a warning reported by Stephen Rothwell ]
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

kernel/irq/manage.c

@@ -768,7 +768,7 @@ int request_irq(unsigned int irq, irq_handler_t handler,
 		kfree(action);
 
 #ifdef CONFIG_DEBUG_SHIRQ
-	if (irqflags & IRQF_SHARED) {
+	if (!retval && (irqflags & IRQF_SHARED)) {
 		/*
 		 * It's a shared IRQ -- the driver ought to be prepared for it
 		 * to happen immediately, so let's make sure....