Re: [Xen-devel] [PATCH] Allow ACPI state change with active cpupools

[Keir Fraser <keir.xen@xxxxxxxxx>]

On 20/03/2012 13:35, "Juergen Gross" <juergen.gross@xxxxxxxxxxxxxx> wrote:

> On 03/20/2012 01:52 PM, Keir Fraser wrote:
>> That's quite a lot of bother. Firstly, this could probably be supported by a
>> global system_state type of variable indicating whether we are booting,
>> suspending, normal. Etc. Secondly I wonder whether you really need to care
>> about this detail from within the cpupool code? When you offline a CPU in
>> cpupool!=0, remember it. Put it back in the pool when it onlines, if the
>> pool still exists. Don't prevent a pool from being destroyed just because it
>> has offline cpus as members. Something like that? Or even always have the
>> cpupool code put onlined cpus in pool 0, and have the acpi suspend code
>> remember and restore pool memberships.
> 
> Hmm. Using a global variable seems to be hacky.

I'm not so sure. Suspend/resume is a significant out-of-the-ordinary global
system state. Representing that in a state variable doesn't seem so bad.
There are other states we could fold into this, for example we have an
early_boot variable in arch/x86 which could become part of the state
enumeration.

> I tried to find a clean
> solution
> for the problem. If the changes are too big in your opinion, I'll try to
> handle
> cpu offlining local to cpupools.

Is it better to have cpupools know about offlining/suspend, or have
offlining/suspend know about cpupools? I would have thought the latter makes
more sense since it is offlining/suspend which calls into the cpupool
subsystem.

 -- Keir

> Thanks for your opinion,



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