[PATCH] x86, irq: get correct available vectors for cpu disable

[Yinghai Lu <yinghai@kernel.org>]

assign_irq_vector will stop before first_system_vector.
also it will not vector that is set in used_vectors.

used_vectors is used to track non per_cpu irq_vector in vector_irq.
It include first 32 exception [0,1f) and system vector near 0xfe.
and IA32_SYSCALL_VECTOR (0x80), IRQ_MOVE_CLEANUP_VECTOR (0x20).

So add checking for them for counting avaiable vectors.

Signed-off-by: Yinghai Lu <yinghai@kernel.org>

---
 arch/x86/kernel/irq.c |   15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

Index: linux-2.6/arch/x86/kernel/irq.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/irq.c
+++ linux-2.6/arch/x86/kernel/irq.c
@@ -321,8 +321,19 @@ int check_irq_vectors_for_cpu_disable(vo
 	for_each_online_cpu(cpu) {
 		if (cpu == this_cpu)
 			continue;
-		for (vector = FIRST_EXTERNAL_VECTOR; vector < NR_VECTORS;
-		     vector++) {
+
+		/*
+		 * assign_irq_vector() only use vector under
+		 * first_system_vector and not set in used_vectors bitmask.
+		 * used_vectors could have bits set for
+		 *	IA32_SYSCALL_VECTOR (0x80)
+		 *	IRQ_MOVE_CLEANUP_VECTOR (0x20)
+		 */
+		for (vector = FIRST_EXTERNAL_VECTOR;
+		     vector < first_system_vector; vector++) {
+			if (test_bit(vector, used_vectors)
+				continue;
+
 			if (per_cpu(vector_irq, cpu)[vector] < 0)
 				count++;
 		}