Re: [PATCH] sched: Do not zero sg->cpumask and sg->sgp->power in build_sched_groups

From: Peter Zijlstra
Date: Tue May 13 2014 - 06:32:52 EST


On Tue, May 13, 2014 at 09:32:53AM +0100, Dietmar Eggemann wrote:
> Hi Peter,
>
> On 30/04/14 14:39, Dietmar Eggemann wrote:
> > From: Dietmar Eggemann <Dietmar.Eggemann@xxxxxxx>
> >
> > There is no need to zero struct sched_group member cpumask and struct
> > sched_group_power member power since both structures are already allocated
> > as zeroed memory in __sdt_alloc().
> >
> > This patch has been tested with
> > BUG_ON(!cpumask_empty(sched_group_cpus(sg))); and BUG_ON(sg->sgp->power);
> > in build_sched_groups() on ARM TC2 and INTEL i5 M520 platform including
> > CPU hotplug scenarios.
> >
> > Signed-off-by: Dietmar Eggemann <dietmar.eggemann@xxxxxxx>
> > ---
> > kernel/sched/core.c | 2 --
> > 1 file changed, 2 deletions(-)
> >
> > diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> > index 9cae286824bb..6bc51aebbf1b 100644
> > --- a/kernel/sched/core.c
> > +++ b/kernel/sched/core.c
> > @@ -5807,8 +5807,6 @@ build_sched_groups(struct sched_domain *sd, int cpu)
> > continue;
> >
> > group = get_group(i, sdd, &sg);
> > - cpumask_clear(sched_group_cpus(sg));
> > - sg->sgp->power = 0;
> > cpumask_setall(sched_group_mask(sg));
> >
> > for_each_cpu(j, span) {
> >
>
> I think this one slipped through the cracks. Could you have a look?

Yeah, got stuck in the backlog :/

Seems simple enough, queued it, we'll see if anything explodes ;-)

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