Re: [PATCH] irqchip/gic-v3-its: fix ITS queue timeout

[Yang Yingliang]

Hi, Julien

On 2018/6/5 18:16, Julien Thierry wrote:
> Hi Yang,
>
> On 05/06/18 07:30, Yang Yingliang wrote:
> > When the kernel booted with maxcpus=x, 'x' is smaller
> > than actual cpu numbers, the TAs of offline cpus won't
> > be set to its->collection.
> >
> > If LPI is bind to offline cpu, sync cmd will use zero TA,
> > it leads to ITS queue timeout.  Fix this by choosing a
> > online cpu, if there is no online cpu in cpu_mask.
> >
> > Signed-off-by: Yang Yingliang <yangyingliang@xxxxxxxxxx>
> > ---
> >   drivers/irqchip/irq-gic-v3-its.c | 9 +++++++--
> >   1 file changed, 7 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/irqchip/irq-gic-v3-its.c 
> > b/drivers/irqchip/irq-gic-v3-its.c
> > index 5416f2b..edd92a9 100644
> > --- a/drivers/irqchip/irq-gic-v3-its.c
> > +++ b/drivers/irqchip/irq-gic-v3-its.c
> > @@ -2309,7 +2309,9 @@ static int its_irq_domain_activate(struct 
> > irq_domain *domain,
> >           cpu_mask = cpumask_of_node(its_dev->its->numa_node);
> >         /* Bind the LPI to the first possible CPU */
> > -    cpu = cpumask_first(cpu_mask);
> > +    cpu = cpumask_first_and(cpu_mask, cpu_online_mask);
> > +    if (!cpu_online(cpu))
>
> Testing for cpu being online here feels a bit redundant.
>
> Since cpu is online if the cpumask_first_and returns a valid cpu, I 
> think you could replace this test with:
>
>     if (cpu >= nr_cpu_ids)
Yes, I used wrong check here, according to comment of cpumask_first_and, 
this func will returns >= nr_cpu_ids if no cpus set in both.

I'll send v2 later.
> > +        cpu = cpumask_first(cpu_online_mask);
> >       its_dev->event_map.col_map[event] = cpu;
> >       irq_data_update_effective_affinity(d, cpumask_of(cpu));
> >   @@ -2466,7 +2468,10 @@ static int its_vpe_set_affinity(struct 
> > irq_data *d,
> >                   bool force)
> >   {
> >       struct its_vpe *vpe = irq_data_get_irq_chip_data(d);
> > -    int cpu = cpumask_first(mask_val);
> > +    int cpu = cpumask_first_and(mask_val, cpu_online_mask);
> > +
> > +    if (!cpu_online(cpu))
>
> Same thing here.
>
> > +        cpu = cpumask_first(cpu_online_mask);
> >         /*
> >        * Changing affinity is mega expensive, so let's be as lazy as
>
> Cheers,

Thanks,
Yang