Is Pandaboard cpuhotplug working stably?

Russell King - ARM Linux linux at
Wed Dec 21 05:07:06 EST 2011

On Wed, Dec 21, 2011 at 05:59:07PM +0800, Barry Song wrote:
> 2011/12/21 Russell King - ARM Linux <linux at>:
> > cpu hotplug is basically totally buggered - the preconditions placed
> > upon the bringup code path are basically impossible to satisfy in any
> > shape or form at the moment.
> >
> > There's the requirement that the secondary CPU is marked online and
> > active before interrupts are enabled for the thread migration stuff
> > to behave correctly.  However, this is incompatible with smp_call_function()
> > which will wait for online CPUs to respond to an IPI - which this one
> > won't because interrupts are disabled.
> >
> > I think there was some discussion about how to fix this but I don't
> > recall the details.
> thanks, Russell. then could i think this is an ARM-kernel-specific bug
> which exists on all ARM SMP chips for the moment?
> and that bug doesn't happen on x86:

I don't think so.  There's nothing ARM specific about it.

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