Subject: [PATCH] prevent powerpc from invoking irq handlers on offline CPUs

From: "Paul E. McKenney" <[email-masked]>
Date: Sun, 31 Aug 2008 10:31:27 -0700

Make powerpc refrain from clearing a given to-be-offlined CPU's bit in the
cpu_online_mask until it has processed pending irqs.  This change
prevents other CPUs from being blindsided by an apparently offline CPU
nevertheless changing globally visible state.

Signed-off-by: Paul E. McKenney <[email-masked]>
---

 smp.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
index 5337ca7..1fedd7d 100644
--- a/arch/powerpc/kernel/smp.c
+++ b/arch/powerpc/kernel/smp.c
@@ -250,11 +250,11 @@ int generic_cpu_disable(void)
 	if (cpu == boot_cpuid)
 		return -EBUSY;
 
-	cpu_clear(cpu, cpu_online_map);
 #ifdef CONFIG_PPC64
 	vdso_data->processorCount--;
 	fixup_irqs(cpu_online_map);
 #endif
+	cpu_clear(cpu, cpu_online_map);
 	return 0;
 }