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SubjectRE: [PATCH] cpu-topology: warn if NUMA configurations conflicts with lower layer
Date
> -----Original Message-----
> From: Valentin Schneider [mailto:valentin.schneider@arm.com]
> Sent: Friday, January 03, 2020 8:15 PM
> To: Zengtao (B); Sudeep Holla
> Cc: Linuxarm; Greg Kroah-Hartman; Rafael J. Wysocki;
> linux-kernel@vger.kernel.org; Morten Rasmussen
> Subject: Re: [PATCH] cpu-topology: warn if NUMA configurations conflicts
> with lower layer
>
> On 03/01/2020 10:57, Valentin Schneider wrote:
> > I'm juggling with other things atm, but let me have a think and see if we
> > couldn't detect that in the scheduler itself.
> >
>
> Something like this ought to catch your case; might need to compare group
> spans rather than pure group pointers.
>

Good suggestion, I will need to have a think and try
Thanks.

> ---
> diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
> index 6ec1e595b1d4..c4151e11afcd 100644
> --- a/kernel/sched/topology.c
> +++ b/kernel/sched/topology.c
> @@ -1120,6 +1120,13 @@ build_sched_groups(struct sched_domain *sd,
> int cpu)
>
> sg = get_group(i, sdd);
>
> + /* sg's are inited as self-looping. If 'last' is not self
> + * looping, we set it in a previous visit. No further visit
> + * should change the link order, if we do then the topology
> + * description is terminally broken.
> + */
> + BUG_ON(last && last->next != last && last->next != sg);
> +
> cpumask_or(covered, covered, sched_group_span(sg));
>
> if (!first)
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