AICT debug printk would help

I stuck with a problem for 2 weeks. Just found out that basic printk would give me
why it happens.
Problem description:
Start 2 VM would panic at insert_vcpu BUG_ON
complaining VCPU already in the runqueue.

Just printk at
insert_vcpu to see whether it is aict context
if (per_cpu(schedule_data, cpu).aict_source)
printk("source domid= %d \n", per_cpu(schedule_data, cpu).aict_source->domain->domain_id);
if (per_cpu(schedule_data, cpu).aict_target)
printk("target domid= %d \n", per_cpu(schedule_data, cpu).aict_target->domain->domain_id);

Should take the lesson and review the problem next time.