Re: [PATCH] powermac: support G5 CPU hotplug

Johannes Berg writes:

This patch allows "hotplugging" of CPUs on G5 machines. CPUs that are
disabled are put into an idle loop with the decrementer frequency set
to minimum. To wake them up again we kick them just like when bringing
them up. To stop those CPUs from messing with any global state we stop
them from entering the timer interrupt.

Ultimately we want to put the disabled cpus in sleep mode, but that
will require a suitable cache flush routine.

For now, the patch mostly looks OK, except that I would prefer that
you make power4_idle_irqs_softdisabled a separate function from
power4_idle (and choose a better name while you're there :).  There
are enough differences between power4_idle and your new routine that
it would be clearer if they're separate.  For one thing your new
routine wouldn't need to set _TLF_NAPPING, for another, it wouldn't
need the conditional branch at the end.  Also you could do the test
for the nap capability in the caller.

Paul.