1 files changed, 23 insertions, 0 deletions

diff --git a/arch/x86/kernel/irq.c b/arch/x86/kernel/irq.c
index 3b9128498976..ccf6c503fc3b 100644
--- a/arch/x86/kernel/irq.c
+++ b/arch/x86/kernel/irq.c
@@ -12,6 +12,29 @@
 
 atomic_t irq_err_count;
 
+/*
+ * 'what should we do if we get a hw irq event on an illegal vector'.
+ * each architecture has to answer this themselves.
+ */
+void ack_bad_irq(unsigned int irq)
+{
+        printk(KERN_ERR "unexpected IRQ trap at vector %02x\n", irq);
+
+#ifdef CONFIG_X86_LOCAL_APIC
+        /*
+         * Currently unexpected vectors happen only on SMP and APIC.
+         * We _must_ ack these because every local APIC has only N
+         * irq slots per priority level, and a 'hanging, unacked' IRQ
+         * holds up an irq slot - in excessive cases (when multiple
+         * unexpected vectors occur) that might lock up the APIC
+         * completely.
+         * But only ack when the APIC is enabled -AK
+         */
+        if (cpu_has_apic)
+                ack_APIC_irq();
+#endif
+}
+
 #ifdef CONFIG_X86_32
 # define irq_stats(x)           (&per_cpu(irq_stat,x))
 #else