RE: [PATCH] cpu-topology: warn if NUMA configurations conflicts with lower layer

[Zengtao (B)]

> -----Original Message-----
> From: Valentin Schneider [mailto:valentin.schneider@xxxxxxx]
> Sent: Friday, January 03, 2020 8:15 PM
> To: Zengtao (B); Sudeep Holla
> Cc: Linuxarm; Greg Kroah-Hartman; Rafael J. Wysocki;
> linux-kernel@xxxxxxxxxxxxxxx; 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)