Re: [PATCH] ARM: do not mark CPU 0 as hotpluggable

On Wed, Jul 20, 2011 at 04:32:25PM -0700, Mike Turquette wrote:

A quick poll of the ARM platforms that implement CPU Hotplug support shows that every platform treats CPU 0 as a special case that cannot be hotplugged. In fact every platform has identical code for platform_cpu_die which returns -EPERM in the case of CPU 0.

Are you sure that's just not because everyone copied what Realview has been doing (highly likely)?

I suspect that there's no reason that CPU0 can't be taken down, especially on those platforms which don't take the CPU fully offline but just put it into a WFI loop.

Those which restart the CPUs through the boot loader probably detect CPU0 as the boot CPU, so they probably can't take CPU0 down.