[PATCH] powerpc: check_and_cede_processor never cedes

Commit f948501b36c6 ("Make hard_irq_disable() actually hard-disable
interrupts") caused check_and_cede_processor to stop working.
->irq_happened will never be zero right after a hard_irq_disable
so the compiler removes the call to cede_processor completely.

The bug was introduced back in the lazy interrupt handling rework
of 3.4 but was hidden until recently because hard_irq_disable did
nothing.

This issue will eventually appear in 3.4 stable since the
hard_irq_disable fix is marked stable, so mark this one for stable
too.

Signed-off-by: Anton Blanchard <redacted>  
Cc: stable@vger.kernel.org
---

Index: linux-build/arch/powerpc/platforms/pseries/processor_idle.c
===================================================================

--- linux-build.orig/arch/powerpc/platforms/pseries/processor_idle.c	2012-06-27 21:20:45.403761715 +1000
+++ linux-build/arch/powerpc/platforms/pseries/processor_idle.c	2012-06-27 21:57:14.796788823 +1000

@@ -106,7 +106,7 @@ static void check_and_cede_processor(voi
 	 * we first hard disable then check.
 	 */
 	hard_irq_disable();
-	if (get_paca()->irq_happened == 0)
+	if (get_paca()->irq_happened == PACA_IRQ_HARD_DIS)
 		cede_processor();
 }