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[Xen-devel] [PATCH v2 1/2] x86: skip migrating IRQF_PER_CPU irq in fixup_irqs

x86: skip migrating IRQF_PER_CPU irq in fixup_irqs

IRQF_PER_CPU marks a irq binding to a specific cpu, and can never be
moved away from that cpu. So it shouldn't be migrated when fixup irqs
to offline a cpu. Xen pvops guest is one source using IRQF_PER_CPU
on a set of virtual interrupts. Previously no error is observed 
because Xen event chip silently fails the set_affinity ops, and
logically IRQF_PER_CPU should be recognized here.

Signed-off-by: Fengzhe Zhang <fengzhe.zhang@xxxxxxxxx>
Signed-off-by: Kevin Tian <kevin.tian@xxxxxxxxx>
CC: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CC: Ingo Molnar <mingo@xxxxxxxxxx>
CC: H. Peter Anvin <hpa@xxxxxxxxx>
CC: Ian Campbell <Ian.Campbell@xxxxxxxxxx>
CC: Jan Beulich <JBeulich@xxxxxxxxxx>

--- linux-2.6.39-rc6.orig/arch/x86/kernel/irq.c 2011-05-04 10:59:13.000000000 
+++ linux-2.6.39-rc6/arch/x86/kernel/irq.c      2011-05-06 09:20:25.563963000 
@@ -249,7 +250,7 @@ void fixup_irqs(void)
                data = irq_desc_get_irq_data(desc);
                affinity = data->affinity;
-               if (!irq_has_action(irq) ||
+               if (!irq_has_action(irq) || irqd_is_per_cpu(data) ||
                    cpumask_subset(affinity, cpu_online_mask)) {

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