Re: [PATCH] xen: fix for_each_cpu when NR_CPUS=1

[Dario Faggioli <dfaggioli@xxxxxxxx>]

On Thu, 2021-03-11 at 12:28 +0100, Jan Beulich wrote:
> On 11.03.2021 10:40, Dario Faggioli wrote:
> > 
> > Removing the special casing of NR_CPUS == 1 makes things work again.
> > 
> > Signed-off-by: Dario Faggioli <dfaggioli@xxxxxxxx>
> 
> Doesn't this want a Reported-by: Roger?
> 
It definitely does! And I even forgot to Cc him... Sorry Roger :-(

Will you add it, or do you want me to resubmit with it?

> Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
> 
Thanks

> And FTR I don't really mind the other NR_CPUS == 1 piece of logic to
> remain there.
> 
Ok. I agree with Juergen that they're totally useless, but at least
they're not wrong.

Oh, BTW, since you mentioned in your other email the fact that this
comes from Linux, I've had a look there and there's a comment in their
cpumask.h file, under the NR_CPUS==1 define, looking like this:

/* Uniprocessor.  Assume all masks are "1". */

https://elixir.bootlin.com/linux/latest/source/include/linux/cpumask.h#L149

Of course, that does not make the fact that for_each_cpu and
for_each_cpu_not are identical less weird, and the whole thing still
does not make sense, at least not to me.

I'm wondering whether or not it is worth to report this to them too, as
I have the impression that they just don't care.

Thanks and Regards
-- 
Dario Faggioli, Ph.D
http://about.me/dario.faggioli
Virtualization Software Engineer
SUSE Labs, SUSE https://www.suse.com/
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