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SubjectRe: [PATCH linux-next v3 1/2] irq: Add CPU mask affinity hint
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 ?

Thanks,

tglx


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