Re: [PATCH tip/core/rcu 8/9] nohz_full: Add full-system-idle state machine

Frederic Weisbecker
2013-09-08T10:46:45Z

On Sun, Sep 08, 2013 at 12:32:50PM +0200, Yann E. MORIN wrote:
> Paul, All,
>
> On 2013-09-07 11:57 -0700, Paul E. McKenney spake thusly:
> > On Sat, Sep 07, 2013 at 11:13:48AM +0200, Yann E. MORIN wrote:
> [--SNIP--]
> > > I'll see if I can come up with a meaningfull construct that fixes your
> > > use-case. Don't hold your breath, though! ;-)
> >
> > If not, we need to add NR_CPUS to the architectures lacking them...
>
> Unfortunately, I was not able to come up with anything suitable.
>
> I think your proposal to always define NR_CPUS=1 for architectures
> without SMP support is a good solution.
>
> After all, if !SMP because the architecture does not support it, I
> believe it makes sense that NR_CPUS be defined to 1.
>
> Unless NR_CPUS carries with it a hidden meaning about SMP being
> possible, that is, which would probably be wrong anyway, since we have
> SMP for this.

Right, if possible, the best would be to define CONFIG_NR_CPUS to a single
central place, like arch/Kconfig:

config NR_CPUS
default 1 if !SMP

It's a single int after all. Specific arch constraints can probably be overriden
from the arch.

>
> Regards,
> Yann E. MORIN.
>
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