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Subject[PATCH] prevent sparc64 from invoking irq handlers on offline CPUs
Make sparc64 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@linux.vnet.ibm.com>
---

smp.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/sparc64/kernel/smp.c b/arch/sparc64/kernel/smp.c
index 743ccad..b83a683 100644
--- a/arch/sparc64/kernel/smp.c
+++ b/arch/sparc64/kernel/smp.c
@@ -1305,10 +1305,6 @@ int __cpu_disable(void)
c->core_id = 0;
c->proc_id = -1;

- spin_lock(&call_lock);
- cpu_clear(cpu, cpu_online_map);
- spin_unlock(&call_lock);
-
smp_wmb();

/* Make sure no interrupts point to this cpu. */
@@ -1318,6 +1314,10 @@ int __cpu_disable(void)
mdelay(1);
local_irq_disable();

+ spin_lock(&call_lock);
+ cpu_clear(cpu, cpu_online_map);
+ spin_unlock(&call_lock);
+
return 0;
}


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