[PATCH] x86_64: Survive having no irq mapping for a vector

[Eric W. Biederman]

Occasionally the kernel has bugs that result in no irq being found for
a given cpu vector.  If we acknowledge the irq the system has a good
chance of continuing even though we dropped an irq message.  If we
continue to simply print a message and not acknowledge the irq the
system is likely to become non-responsive shortly there after. 

Signed-off-by: Eric W. Biederman <ebiederm@xxxxxxxxxxxx>
---
 arch/x86_64/kernel/irq.c |   11 ++++++++---
 1 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/arch/x86_64/kernel/irq.c b/arch/x86_64/kernel/irq.c
index 0c06af6..648055a 100644
--- a/arch/x86_64/kernel/irq.c
+++ b/arch/x86_64/kernel/irq.c
@@ -120,9 +120,14 @@ asmlinkage unsigned int do_IRQ(struct pt_regs *regs)
 
 	if (likely(irq < NR_IRQS))
 		generic_handle_irq(irq);
-	else if (printk_ratelimit())
-		printk(KERN_EMERG "%s: %d.%d No irq handler for vector\n",
-			__func__, smp_processor_id(), vector);
+	else {
+		if (!disable_apic)
+			ack_APIC_irq();
+
+		if (printk_ratelimit())
+			printk(KERN_EMERG "%s: %d.%d No irq handler for vector\n",
+				__func__, smp_processor_id(), vector);
+	}
 
 	irq_exit();
 
-- 
1.4.4.1.g278f

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