[PATCH] x86/x86_64: warn of -EBUSY returns from __assign_irq_vector()

[Gary Hade <garyhade@us.ibm.com>]

Impact: helps expose unexpected issues

Since we have seen one case where an unexpected -EBUSY
return from __assign_irq_vector() was included in the
series of events that caused a serious problem
  re: http://lkml.org/lkml/2009/6/2/377
we should warn to help expose similar unexpected issues
in the future.

Signed-off-by: Gary Hade <garyhade@us.ibm.com>

---
 arch/x86/kernel/apic/io_apic.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

Index: linux-2.6.30-rc8/arch/x86/kernel/apic/io_apic.c
===================================================================
--- linux-2.6.30-rc8.orig/arch/x86/kernel/apic/io_apic.c	2009-06-08 09:56:15.000000000 -0700
+++ linux-2.6.30-rc8/arch/x86/kernel/apic/io_apic.c	2009-06-08 09:56:27.000000000 -0700
@@ -1330,8 +1330,10 @@ __assign_irq_vector(int irq, struct irq_
 	int cpu, err;
 	cpumask_var_t tmp_mask;
 
-	if ((cfg->move_in_progress) || cfg->move_cleanup_count)
+	if ((cfg->move_in_progress) || cfg->move_cleanup_count) {
+		WARN_ON_ONCE(1);
 		return -EBUSY;
+	}
 
 	if (!alloc_cpumask_var(&tmp_mask, GFP_ATOMIC))
 		return -ENOMEM;