> /proc/cpuinfo said kernel detected both cpus, but 2nd cpu did not work.
> It means 2nd cpu kept running idle tasks.
>
> We think that value of has_cpu flag in idle task is the cause of this
> problem.
>
> Even if 2nd cpu has idle task, has_cpu flag in idle task is not set.
>
> Therefore scheduler can't deliver new tasks to 2nd cpu.
> (keeps running idle task.)
yes but this happens only until the first reschedule happens on the second
CPU. I suspect all interrupts are delivered to the first CPU on your
system for some reason, correct? In that case the idle thread on the
second CPU is never directly rescheduled by an interrupt. [btw., i've
recently fixed it the same way you did in my tree, and this is not the
only problem in that area, another problem is that the first time the idle
thread is started up we might reschedule before it has gotten it's
'proper' stack, which can cause a rather subtle and silent memory
corruption. I suspect could be the reason why certain kernel builds have
problems booting under SMP. I'll send a full patch for both of these
problems this week.]
-- mingo
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