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SubjectRe: [sched] fix sched_domains hotplug bootstrap ordering vs. cpu_online_map issue

* William Lee Irwin III <wli@holomorphy.com> wrote:

> William Lee Irwin III <wli@holomorphy.com> wrote:
> >> This is the whole thing; the "other half" referred to a new hunk added to
> >> the patch (identical to this one) posted in its entirety.
>
> On Fri, Sep 03, 2004 at 03:34:34PM -0700, Andrew Morton wrote:
> > ho-hum. changelog, please?
>
> cpu_online_map is not set up at the time of sched domain
> initialization when hotplug cpu paths are used for SMP booting. At
> this phase of bootstrapping, cpu_possible_map can be used by the
> various architectures using cpu hotplugging for SMP bootstrap, but the
> manipulations of cpu_online_map done on behalf of NUMA architectures,
> done indirectly via node_to_cpumask(), can't, because cpu_online_map
> starts depopulated and hasn't yet been populated. On true NUMA
> architectures this is a distinct cpumask_t from cpu_online_map and so
> the unpatched code works on NUMA; on non-NUMA architectures the
> definition of node_to_cpumask() this way breaks and would require an
> invasive sweeping of users of node_to_cpumask() to change it to e.g.
> cpu_possible_map, as cpu_possible_map is not suitable for use at
> runtime as a substitute for cpu_online_map.
>
> Signed-off-by: William Irwin <wli@holomorphy.com>

Signed-off-by: Ingo Molnar <mingo@elte.hu>

Ingo
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