On Saturday, 28 July 2007 18:55, Linus Torvalds wrote:
>
> On Sat, 28 Jul 2007, Linus Torvalds wrote:
> >
> > And it's the *top*level* code that selects HOTPLUG_CPU. Through
> > SUSPEND_SMP (which will select HOTPLUG_CPU) and SOFTWARE_SUSPEND.
>
> In other words, the problem seems to be that
>
> kernel/power/main.c:
> suspend_devices_and_enter()
>
> does the proper "disable/enable_nonboot_cpus()", but it does so without
> having enabled CPU hotplug.
>
> And you seem to think that it's ACPI that should enable the hotplug, even
> though the code that actually needs it is _outside_ ACPI. And I think
> that's wrong, and that this is a bug.
>
> So I think the real issue is that we allow that
> "suspend_devices_and_enter()" code to be compiled without HOTPLUG_CPU in
> the first place. It's not supposed to work that way.
>
> Of course, it may well be that other architectures can happily suspend
> even with multiple CPU's active, which may be the cause of this mess. But
> I really think it shouldn't be ACPI that has to select the CPU hotplug,
> since it's not ACPI that _uses_ it in the first place.
>
> Rafael: making a config option for STR (the same way we have a config
> option for hibernate), and just not allowing it on SMP without HOTPLUG_CPU
> seems to be the right thing. Len is right in that we do insane things
> right now (trying to STR with multiple CPU's still active), and I just
> don't think he's the one that should work around it!
Well, I agree and that's why I asked. :-)
OK, I'll prepare a patch to introduce CONFIG_SUSPEND, but that will require
quite a bit of (compilation) testing on different architectures.
Greetings,
Rafael
--
"Premature optimization is the root of all evil." - Donald Knuth
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