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Subject[PATCH] CPEI gets warning at kernel/irq/migration.c:27/move_masked_irq()

While running my MCA test (hardware error injection) on 2.6.19,
I got some warning like following:

> BUG: warning at kernel/irq/migration.c:27/move_masked_irq()
> Call Trace:
> [<a000000100013d20>] show_stack+0x40/0xa0
> sp=e00000006b2578d0 bsp=e00000006b2510b0
> [<a000000100013db0>] dump_stack+0x30/0x60
> sp=e00000006b257aa0 bsp=e00000006b251098
> [<a0000001000de430>] move_masked_irq+0xb0/0x240
> sp=e00000006b257aa0 bsp=e00000006b251070
> [<a0000001000de6a0>] move_native_irq+0xe0/0x180
> sp=e00000006b257aa0 bsp=e00000006b251040
> [<a00000010004ff50>] iosapic_end_level_irq+0x30/0xe0
> sp=e00000006b257aa0 bsp=e00000006b251020
> [<a0000001000d94d0>] __do_IRQ+0x170/0x400
> sp=e00000006b257aa0 bsp=e00000006b250fd8
> [<a0000001000116f0>] ia64_handle_irq+0x1b0/0x260
> sp=e00000006b257aa0 bsp=e00000006b250fa8
> [<a00000010000c3a0>] ia64_leave_kernel+0x0/0x280
> sp=e00000006b257aa0 bsp=e00000006b250fa8
> [<a000000100690cf0>] _spin_unlock_irqrestore+0x30/0x60
> sp=e00000006b257c70 bsp=e00000006b250f90

It comes from:

26 if (CHECK_IRQ_PER_CPU(desc->status)) {
27 WARN_ON(1);
28 return;
29 }

By putting some printk in kernel, I found that irqbalance is trying to
move CPEI which is handled as PER_CPU irq. That's why.

CPEI(Corrected Platform Error Interrupt) is ia64 specific irq, is
allowed to pin to particular processor which selected by the platform, and
even it is PER_CPU but it has set_affinity handler (=iosapic_set_affinity)
as same as other IO-SAPIC-level interrupts. (I don't know why, but
I guess that there would be typical situation where the handler for
migration is needed, such as hotplug - the processor going to be

To shut up this warning, there are 2 way at least:
a) fix CPEI stuff
b) prohibit setting affinity to PER_CPU irq

I'm not sure what stuff of CPEI need to be fixed, but I think that
returning error to attempting move PER_CPU irq is useful for all
applications since it will never work.

Following small patch takes b) style.
It works, the warning disappeared and irqbalance still runs well.


Signed-off-by: Hidetoshi Seto <>

kernel/irq/proc.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

Index: linux-2.6.19/kernel/irq/proc.c
--- linux-2.6.19.orig/kernel/irq/proc.c
+++ linux-2.6.19/kernel/irq/proc.c
@@ -54,7 +54,8 @@ static int irq_affinity_write_proc(struc
unsigned int irq = (int)(long)data, full_count = count, err;
cpumask_t new_value, tmp;

- if (!irq_desc[irq].chip->set_affinity || no_irq_affinity)
+ if (!irq_desc[irq].chip->set_affinity || no_irq_affinity ||
+ CHECK_IRQ_PER_CPU(irq_desc[irq].status))
return -EIO;

err = cpumask_parse_user(buffer, count, new_value);

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