Re: [PATCH linux-next v3 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, Ben Hutchings wrote:
> > On Fri, 2010-04-30 at 13:23 -0700, Peter P Waskiewicz Jr wrote:
> > > +int irq_register_affinity_hint(unsigned int irq, const struct cpumask *m)
> > > +{
> > > +	struct irq_desc *desc = irq_to_desc(irq);
> > > +	unsigned long flags;
> > > +
> > > +	if (!desc)
> > > +		return -EINVAL;
> >
> > Is it possible for irq_to_desc(irq) to be NULL?  This function already
> > assumes that the caller 'owns' the IRQ.
>
> Oh come on. Driver writers get everything wrong and not checking on an
> invalid irq number is better than crashing :)
>
> > > +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;
> > > +	cpumask_var_t mask;
> > > +	int ret = -EINVAL;
> >
> > I don't think this should be returning -EINVAL if the affinity hint is
> > missing.  That means 'invalid argument', but there is nothing invalid
> > about trying to read() the corresponding file.  The file should simply
> > be empty if there is no hint.  (Actually it might be better if it didn't
> > appear at all, but that would be a pain to implement.)
>
> I agree that -EINVAL is not really a good match.
>
> How about just returning CPU_MASK_ALL if desc->affinity_hint is not
> set ?

That seems reasonable to me.

cheers,
-PJ
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