[PATCH] Fail setup_irq for unconfigured IRQs

From: Zwane Mwaikambo <zwane@holomorphy.com>

This patch makes us bail out in case we may have an interrupt which couldn't
be associated with an interrupt controller.  Without this we allow
unconfigured interrupts to be assigned and then later on we get "unexpected
IRQ trap at vector xx" during the ack phase.

scenario: This can occur if we fail irq setup during setup_IO_APIC_irqs for
some reason or other and then miss getting assigned a vector.  Later on we
then get assigned no_irq_type as our handler.

Patch for i386 and x86_64

arch/i386/kernel/irq.c

@@ -744,6 +744,8 @@ int setup_irq(unsigned int irq, struct irqaction * new)
 	struct irqaction *old, **p;
 	irq_desc_t *desc = irq_desc + irq;
 
+	if (desc->handler == &no_irq_type)
+		return -ENOSYS;
 	/*
 	 * Some drivers like serial.c use request_irq() heavily,
 	 * so we have to be careful not to interfere with a

arch/x86_64/kernel/irq.c

@@ -732,6 +732,9 @@ int setup_irq(unsigned int irq, struct irqaction * new)
 	struct irqaction *old, **p;
 	irq_desc_t *desc = irq_desc + irq;
 
+	if (desc->handler == &no_irq_type)
+		return -ENOSYS;
+
 	/*
 	 * Some drivers like serial.c use request_irq() heavily,
 	 * so we have to be careful not to interfere with a