linux-kernel - Re: [tip: sched/urgent] sched/fair: Use sched_domain_span() for topology_span

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Message-ID: <20250704123307.GCaGfKAzoceu9siXCN@fat_crate.local>
Date: Fri, 4 Jul 2025 14:33:07 +0200
From: Borislav Petkov <bp@...en8.de>
To: K Prateek Nayak <kprateek.nayak@....com>
Cc: linux-kernel@...r.kernel.org, linux-tip-commits@...r.kernel.org,
	Leon Romanovsky <leon@...nel.org>,
	Valentin Schneider <vschneid@...hat.com>,
	"Peter Zijlstra (Intel)" <peterz@...radead.org>,
	Steve Wahl <steve.wahl@....com>, x86@...nel.org
Subject: Re: [tip: sched/urgent] sched/fair: Use sched_domain_span() for
 topology_span_sane()

On Fri, Jul 04, 2025 at 05:16:44PM +0530, K Prateek Nayak wrote:
> In an attempt to solve a complicated case, I think I overlooked the
> simplest one.

It happens. No worries.

> Can you try the below incremental diff on top of this patch and

Yap, works. Thanks.

> let me know if you still hit the error:
> 
> (Lightly tested on QEMU)
> 
> diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
> index 0e46068acb0a..cce540fe36c6 100644
> --- a/kernel/sched/topology.c
> +++ b/kernel/sched/topology.c
> @@ -2423,6 +2423,14 @@ static bool topology_span_sane(const struct cpumask *cpu_map)
>  			struct cpumask *sd_span = sched_domain_span(sd);
>  			int id;
> +			/*
> +			 * If the child already covers the cpumap, sd
> +			 * remains un-initialized. Use sd->private to
> +			 * detect uninitialized domains.
> +			 */
> +			if (!sd->private)
> +				continue;
> +
>  			/* lowest bit set in this mask is used as a unique id */
>  			id = cpumask_first(sd_span);
> ---

Yeah, when you send a hunk I should apply, no matter how easy it is, pls send
it from a mail client which doesn't mangle the diff otherwise I get:

$ test-apply.sh -n /tmp/diff
checking file kernel/sched/topology.c
Hunk #1 FAILED at 2423.
1 out of 1 hunk FAILED

Or you can attach it.

I've done it by hand now.

> Thank you for the report and sorry for the oversight.

No worries at all.

> Hope I have not disrupted your Feierabend.

Haha, I have Feierabend a lot later, if at all :-P

I hope you can enjoy the weekend a bit and not look at code too much.

:-)

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette