On 12/30/13, Prarit Bhargava <pra...@redhat.com> wrote:
>
>
> On 12/30/2013 07:56 AM, rui wang wrote:
>
>> An irq can be mapped to only one vector number, but can have multiple
>> destination CPUs. i.e. the same irq/vector can appear on multiple
>> CPUs' vector_irq[]. So checking data->affinity is necessary I think.
>
> That's true Rui -- but here's what I think the scenario actually is.
>
> Suppose we have a 4-cpu system, and we have an IRQ that is mapped to
> multiple
> cpu's vector_irq[]. For example, we have IRQ 200 that is mapped to CPU 2
> vector_irq[50], and CPU 3 vector_irq[60].
>
This should not happen. There's only one LSB to fill the vector number
in IRTE. So either 50 or 60 but not both for an irq.
...
> Okay, so the big issue is that we need to do the calculation without this cpu,
Yes if it's done before calling cpu_disable_comm().
> so I think this works (sorry for the cut-and-paste)
>
> int check_irq_vectors_for_cpu_disable(void)
> {
> int irq, cpu;
> unsigned int vector, this_count, count;
> struct irq_desc *desc;
> struct irq_data *data;
> struct cpumask online_new; /* cpu_online_mask - this_cpu */
> struct cpumask affinity_new; /* affinity - this_cpu */
>
> cpumask_copy(&online_new, cpu_online_mask);
> cpu_clear(smp_processor_id(), online_new);
>
> this_count = 0;
> 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(smp_processor_id(), affinity_new);
> if (irq_has_action(irq) && !irqd_is_per_cpu(data) &&
> !cpumask_subset(&affinity_new, &online_new) &&
> !cpumask_empty(&affinity_new))
If this cpu is the only target, then affinity_new becomes empty.
Should we count it for migration?
Thanks
Rui
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