diff --git a/arch/i386/kernel/io_apic.c b/arch/i386/kernel/io_apic.c
index 2424cc9c7b3d..6a3875f81a0a 100644
--- a/arch/i386/kernel/io_apic.c
+++ b/arch/i386/kernel/io_apic.c
@@ -1227,26 +1227,32 @@ static u8 irq_vector[NR_IRQ_VECTORS] __read_mostly = { FIRST_DEVICE_VECTOR , 0 }
 
 static int __assign_irq_vector(int irq)
 {
-	static int current_vector = FIRST_DEVICE_VECTOR, offset = 0;
-	int vector;
+	static int current_vector = FIRST_DEVICE_VECTOR, current_offset = 0;
+	int vector, offset, i;
 
 	BUG_ON((unsigned)irq >= NR_IRQ_VECTORS);
 
 	if (irq_vector[irq] > 0)
 		return irq_vector[irq];
 
-	current_vector += 8;
-	if (current_vector == SYSCALL_VECTOR)
-		current_vector += 8;
-
-	if (current_vector >= FIRST_SYSTEM_VECTOR) {
-		offset++;
-		if (!(offset % 8))
-			return -ENOSPC;
-		current_vector = FIRST_DEVICE_VECTOR + offset;
-	}
-
 	vector = current_vector;
+	offset = current_offset;
+next:
+	vector += 8;
+	if (vector >= FIRST_SYSTEM_VECTOR) {
+		offset = (offset + 1) % 8;
+		vector = FIRST_DEVICE_VECTOR + offset;
+	}
+	if (vector == current_vector)
+		return -ENOSPC;
+	if (vector == SYSCALL_VECTOR)
+		goto next;
+	for (i = 0; i < NR_IRQ_VECTORS; i++)
+		if (irq_vector[i] == vector)
+			goto next;
+
+	current_vector = vector;
+	current_offset = offset;
 	irq_vector[irq] = vector;
 
 	return vector;