Re: [PATCH linux-next v2 1/2] irq: Add CPU mask affinity hint

[Peter P Waskiewicz Jr]

On Fri, 30 Apr 2010, Thomas Gleixner wrote:

> On Fri, 30 Apr 2010, Peter P Waskiewicz Jr wrote:
>
> > This patch adds a cpumask affinity hint to the irq_desc
> > structure, along with a registration function and a read-only
> > proc entry for each interrupt.
> >
> > This affinity_hint handle for each interrupt can be used by
> > underlying drivers that need a better mechanism to control
> > interrupt affinity.  The underlying driver can register a
> > cpumask for the interrupt, which will allow the driver to
> > provide the CPU mask for the interrupt to anything that
> > requests it.  The intent is to extend the userspace daemon,
> > irqbalance, to help hint to it a preferred CPU mask to balance
> > the interrupt into.
> >
> > Signed-off-by: Peter P Waskiewicz Jr <peter.p.waskiewicz.jr@xxxxxxxxx>
> > ---
> >
> >  include/linux/interrupt.h |   13 +++++++++++++
> >  include/linux/irq.h       |    1 +
> >  kernel/irq/manage.c       |   28 ++++++++++++++++++++++++++++
> >  kernel/irq/proc.c         |   33 +++++++++++++++++++++++++++++++++
> >  4 files changed, 75 insertions(+), 0 deletions(-)
> >
> > diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
> > index 75f3f00..9c9ea2a 100644
> > --- a/include/linux/interrupt.h
> > +++ b/include/linux/interrupt.h
> > @@ -209,6 +209,9 @@ extern int irq_set_affinity(unsigned int irq, const struct cpumask *cpumask);
> >  extern int irq_can_set_affinity(unsigned int irq);
> >  extern int irq_select_affinity(unsigned int irq);
> >
> > +extern int irq_register_affinity_hint(unsigned int irq,
> > +                                      const struct cpumask *m);
>
> I think we can do with a single funtion irq_set_affinity_hint() and
> let the caller set the pointer to NULL.

That works too.  I like it.  :-)

> > +int irq_register_affinity_hint(unsigned int irq, const struct cpumask *m)
> > +{
> > +	struct irq_desc *desc = irq_to_desc(irq);
> > +	unsigned long flags;
>
>  desc needs to be checked. It might be NULL !

Doh, good point!

> > +
> > +	raw_spin_lock_irqsave(&desc->lock, flags);
> > +	desc->affinity_hint = m;
> > +	raw_spin_unlock_irqrestore(&desc->lock, flags);
> > +
> > +	return 0;
> > +}
> > +EXPORT_SYMBOL(irq_register_affinity_hint);
>
>  EXPORT_SYMBOL_GPL please

Will do.

> > +static int irq_affinity_hint_proc_show(struct seq_file *m, void *v)
> > +{
> > +	struct irq_desc *desc = irq_to_desc((long)m->private);
> > +	unsigned long flags;
> > +	int ret = -EINVAL;
> > +
> > +	raw_spin_lock_irqsave(&desc->lock, flags);
> > +	if (desc->affinity_hint) {
> > +		seq_cpumask(m, desc->affinity_hint);
>
>  Please make a local copy under desc->mask and do the seq_cpumask()
>  stuff on the local copy outside of desc->lock

Will do.

Cheers,

-PJ
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