Re: [PATCH 01/10] cpumask: Introduce cpumask_any_online_but

[Vikas Shivappa]

On Mon, 15 Jun 2015, Peter Zijlstra wrote:

> On Fri, Jun 12, 2015 at 11:17:08AM -0700, Vikas Shivappa wrote:
> > There is currently no cpumask helper function to pick a "random" cpu
> > from a mask which is also online.
> >
> > cpumask_any_online_but() does that which is similar to cpumask_any_but()
> > but also returns a cpu that is online.
> >
> > Signed-off-by: Vikas Shivappa <vikas.shivappa@xxxxxxxxxxxxxxx>
> > ---
> >  include/linux/cpumask.h | 18 ++++++++++++++++++
> >  1 file changed, 18 insertions(+)
> >
> > diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h
> > index 27e285b..f2d7e8a 100644
> > --- a/include/linux/cpumask.h
> > +++ b/include/linux/cpumask.h
> > @@ -548,6 +548,24 @@ static inline void cpumask_copy(struct cpumask *dstp,
> >  #define cpumask_of(cpu) (get_cpu_mask(cpu))
> >
> >  /**
> > + * cpumask_any_online_but - return a "random"  and online cpu in a cpumask,
> > + * but not this one
> > + * @mask: the input mask to search
> > + * @cpu: the cpu to ignore
> > + *
> > + * Returns >= nr_cpu_ids if no cpus set.
> > +*/
> > +static inline unsigned int cpumask_any_online_but(const struct cpumask *mask,
> > +					   unsigned int cpu)
> > +{
> > +	cpumask_t tmp;
>
> No, you cannot put a cpumask_t on stack like that. Those things can be
> massive.

ok , Will fix.

> > +
> > +	cpumask_and(&tmp, cpu_online_mask, mask);
> > +	cpumask_clear_cpu(cpu, &tmp);
> > +	return cpumask_any(&tmp);
> > +}
>
> You had a good example in cpumask_any_but() copy that.

I saw the cpumask_any_but but wanted to avoid the 
for loop in the cpumask_any_but , but now i see why from your previous comment. 
Without the cpumask_t I will have to use the cpumask_any_but .. the two were 
related.

Thanks,
Vikas

>
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