2.6.33-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Johannes Berg <johannes@sipsolutions.net>

commit 3cd8519248e9e17d982c6fab0f1a89bca6feb49a upstream.

When SPARSE_IRQ is set, irq_to_desc() can
return NULL. While the code here has a
check for NULL, it's not really correct.
Fix it by separating the check for it.

This fixes CPU hot unplug for me.

Reported-by: Alastair Bridgewater <alastair.bridgewater@gmail.com>
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
 arch/powerpc/kernel/irq.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

--- a/arch/powerpc/kernel/irq.c
+++ b/arch/powerpc/kernel/irq.c
@@ -247,7 +247,10 @@ void fixup_irqs(cpumask_t map)
 		cpumask_t mask;
 
 		desc = irq_to_desc(irq);
-		if (desc && desc->status & IRQ_PER_CPU)
+		if (!desc)
+			continue;
+
+		if (desc->status & IRQ_PER_CPU)
 			continue;
 
 		cpumask_and(&mask, desc->affinity, &map);