On Sat, Mar 25, 2006 at 04:15:59AM -0800, Andrew Morton wrote:
> Russell King <[email protected]> wrote:
> > With your proposed change,
>
> Which proposed change? I proposed two.
The latter change.
> > if a SMP system with has 4 possible CPUs
> > was passed maxcpus=1, cpu_possible_map may well have 4 CPUs, and
> > cpu_present_map will only contain the one. However, due to the
> > fixup_cpu_present_map(), it will say "oh only one CPU, we need to
> > populate the others" and so you'd actually try to boot all 4.
>
> The change we appear to be going with is to remove fixup_cpu_present_map()
> which appears to address this.
>
> > So no, this doesn't work.
>
> What doesn't work?
The situation I described and you've quoted in the bulk of the above
quote.
> > Isn't it about time the pre-CPU hotplug SMP
> > stuff was updated, rather than trying to messily support two different
> > SMP initialisation methodologies in generic code with band aid plasters
> > all over?
>
> What two methodologies? arch-doing-it and fixup_cpu_present_map() doing it?
What I'm referring to is the pre-CPU hotplug SMP initialisation
methodology and the post-CPU hotplug SMP initialisation methodology,
which I think is covered by "two different SMP initialisation
methodologies".
The two methodologies had entirely different ways of bringing up the
non-boot CPUs to the extent of using the cpu_*_map variables in different
ways. However, now that I come to look again at x86, the situation does
appear to have improved somewhat over the last year or so since I last
looked (which was when I sorted out the ARM SMP support.)
--
Russell King
Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/
maintainer of: 2.6 Serial core
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