linux-kernel - [PATCH] prevent powerpc from invoking irq handlers on offline CPUs

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Date:	Sun, 31 Aug 2008 10:31:27 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	linux-kernel@...r.kernel.org
Cc:	paulus@...ba.org, benh@...nel.crashing.org,
	jwboyer@...ux.vnet.ibm.com, tnt@...tNt.com,
	grant.likely@...retlab.ca, linuxppc-dev@...abs.org,
	manfred@...orfullife.com, akpm@...ux-foundation.org
Subject: [PATCH] prevent powerpc from invoking irq handlers on offline CPUs

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 <paulmck@...ux.vnet.ibm.com>
---

 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;
 }
 
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