[PATCH 02/12] powermac: support G5 CPU hotplug

[Johannes Berg]

On Wed, 2007-02-07 at 13:45 +0100, Johannes Berg wrote:

> Except for the in-irq count hack I'm happy with this. I still haven't found
> where the in-hard-irq count is set to 1 in the down path during suspend or
> resume and other platforms do similar things so I'm inclined to leave this.

Um, ok, so the hack breaks platforms that don't have paca, e.g. chrp32.

Also, I finally figured out how the in-hard-irq count happens. The thing
is that when I try to turn off the CPU it actually doesn't really turn
off of course, so it ends up doing NAP and taking timer interrupts...
which goes irq_enter() and we happen to kill it afterwards.

I have two ways of fixing this:
 - just ignore it as we do now
 - insert a "if (cpu_dead) return" into the timer interrupt function

I prefer the latter because then we're guaranteed that whatever the
timer interrupt does we don't modify any state for/by the CPU that isn't
supposed to exist.

johannes
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