On 01/07/2014 12:54 PM, Luck, Tony wrote:
> + for (vector = FIRST_EXTERNAL_VECTOR; vector < NR_VECTORS; vector++) {
> + irq = __this_cpu_read(vector_irq[vector]);
> + if (irq >= 0) {
> + desc = irq_to_desc(irq);
> + data = irq_desc_get_irq_data(desc);
> + cpumask_copy(&affinity_new, data->affinity);
> + cpu_clear(this_cpu, affinity_new);
> + /*
> + * The check below determines if this irq requires
> + * an empty vector_irq[irq] entry on an online
> + * cpu.
> + *
> + * The code only counts active non-percpu irqs, and
> + * those irqs that are not linked to on an online cpu.
> + * The first test is trivial, the second is not.
> + *
> + * The second test takes into account the
> + * account that a single irq may be mapped to multiple
> + * cpu's vector_irq[] (for example IOAPIC cluster
> + * mode). In this case we have two
> + * possibilities:
> + *
> + * 1) the resulting affinity mask is empty; that is
> + * this the down'd cpu is the last cpu in the irq's
> + * affinity mask, and
> Code says "||" - so I think comment should say "or".
> + *
> + * 2) the resulting affinity mask is no longer
> + * a subset of the online cpus but the affinity
> + * mask is not zero; that is the down'd cpu is the
> + * last online cpu in a user set affinity mask.
> + *
> + * In both possibilities, we need to remap the irq
> + * to a new vector_irq[].
> + *
> + */
> + if (irq_has_action(irq) && !irqd_is_per_cpu(data) &&
> + (cpumask_empty(&affinity_new) ||
> + !cpumask_subset(&affinity_new, &online_new)))
> + this_count++;
> + }
>
> That's an impressive 6:1 ratio of lines-of-comment to lines-of-code!
Heh -- I couldn't decide if I should keep it all together in one comment or
divide it up. I guess it does look less scary if I divide it up. So how about
(sorry for the cut-and-paste)
for (vector = FIRST_EXTERNAL_VECTOR; vector < NR_VECTORS; vector++) {
irq = __this_cpu_read(vector_irq[vector]);
if (irq >= 0) {
desc = irq_to_desc(irq);
data = irq_desc_get_irq_data(desc);
cpumask_copy(&affinity_new, data->affinity);
cpu_clear(this_cpu, affinity_new);
/* Do not count inactive or per-cpu irqs. */
if (!irq_has_action(irq) || irqd_is_per_cpu(data))
continue;
/*
* A single irq may be mapped to multiple
* cpu's vector_irq[] (for example IOAPIC cluster
* mode). In this case we have two
* possibilities:
*
* 1) the resulting affinity mask is empty; that is
* this the down'd cpu is the last cpu in the irq's
* affinity mask, or
*
* 2) the resulting affinity mask is no longer
* a subset of the online cpus but the affinity
* mask is not zero; that is the down'd cpu is the
* last online cpu in a user set affinity mask.
*/
if (cpumask_empty(&affinity_new) ||
!cpumask_subset(&affinity_new, &online_new))
this_count++;
}
}
Everyone okay with that?
P.
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