Re: [PATCH] prevent ia64 from invoking irq handlers on offline CPUs

On Sun, Aug 31, 2008 at 07:46:33PM +0200, Vegard Nossum wrote:
On Sun, Aug 31, 2008 at 7:28 PM, Paul E. McKenney
<paulmck@xxxxxxxxxxxxxxxxxx> wrote:
Make ia64 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@xxxxxxxxxxxxxxxxxx>
---

smpboot.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/ia64/kernel/smpboot.c b/arch/ia64/kernel/smpboot.c
index bcea81e..7a90f42 100644
--- a/arch/ia64/kernel/smpboot.c
+++ b/arch/ia64/kernel/smpboot.c
@@ -741,8 +741,6 @@ int __cpu_disable(void)
return -EBUSY;
}

- cpu_clear(cpu, cpu_online_map);
-
if (migrate_platform_irqs(cpu)) {
cpu_set(cpu, cpu_online_map);
return (-EBUSY);
@@ -751,6 +749,7 @@ int __cpu_disable(void)
remove_siblinginfo(cpu);
cpu_clear(cpu, cpu_online_map);
fixup_irqs();
+ cpu_clear(cpu, cpu_online_map);
local_flush_tlb_all();
cpu_clear(cpu, cpu_callin_map);
return 0;

Hm. Maybe my eyes are going bad. But isn't that now clearing the cpu
both before and after calling fixup_irqs()?

I don't believe so... I removed the earlier one and added the later
one. Or is there another one hidden somewhere that I missed?

Thanx, Paul
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