--- linux-2.6/arch/x86_64/kernel/io_apic.c	2006-10-24 13:40:48.000000000 -0700
+++ linux-2.6.xx/arch/x86_64/kernel/io_apic.c	2006-10-24 14:03:08.000000000 -0700
@@ -716,6 +716,22 @@
 	return vector;
 }
 
+static void __clear_irq_vector(int irq)
+{
+	int old_vector = -1;
+	if (irq_vector[irq] > 0)
+		old_vector = irq_vector[irq];
+	if (old_vector >= 0) {
+		cpumask_t old_mask;
+		int old_cpu;
+		cpus_and(old_mask, irq_domain[irq], cpu_online_map);
+		for_each_cpu_mask(old_cpu, old_mask)
+			per_cpu(vector_irq, old_cpu)[old_vector] = -1;
+	}
+	irq_vector[irq] = 0;
+	irq_domain[irq] = CPU_MASK_NONE;
+}
+
 void __setup_vector_irq(int cpu)
 {
 	/* Initialize vector_irq on a new cpu */
@@ -1803,7 +1819,7 @@
 	dynamic_irq_cleanup(irq);
 
 	spin_lock_irqsave(&vector_lock, flags);
-	irq_vector[irq] = 0;
+	__clear_irq_vector(irq);
 	spin_unlock_irqrestore(&vector_lock, flags);
 }