Is Pandaboard cpuhotplug working stably?

[Shilimkar, Santosh]

+ Peter Z

On Wed, Dec 21, 2011 at 3:37 PM, Russell King - ARM Linux
<linux at arm.linux.org.uk> wrote:
> On Wed, Dec 21, 2011 at 05:59:07PM +0800, Barry Song wrote:
>> 2011/12/21 Russell King - ARM Linux <linux at arm.linux.org.uk>:
>> > 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.

There are few patches floating around for this issue. I posted one version
long back [1] and then there was one more form Thomas G.
The most recent is from one is from Peter Z [2] which is moving the
fix for the cup online race to core code.

Can you try Peter's patch with your test-case ?

Regards,
Santosh

[1] https://lkml.org/lkml/2011/6/20/79
[2] https://lkml.org/lkml/2011/12/15/255