Re: [PATCH] x86: Document the hotplug code is incompatible with x86 irq handling

Robert Hancock
2007-05-31T14:34:48Z

Eric W. Biederman wrote:
> I just realized that except for doing the code review and noticing
> that the current cpu hotplug code is fundamentally incompatible
> with x86 I haven't done anything about it. So here is my patch
> to document what is wrong.
>
> The current cpu hotplug code requires irqs to be migrated from a cpu
> outside of irq context. On x86 ioapics simply do not support this,
> making the code unfixable without major redesign of the generic cpu
> hotplug code.
>
> So this patch makes CPU_HOTPLUG on x86 depend on CONFIG_BROKEN
> and adds a WARN_ON so people that do enable it are not in doubt about
> which part of the code is broken, even if it does work for them.
>
> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>

I don't think this is useful, though the code may be problematic, this
patch will break suspend on all SMP machines with an existing config,
which is a major regression..

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Robert Hancock Saskatoon, SK, Canada
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