linux-kernel - Re: [PATCH 06/14] sched/topology,debug: Verify the first group matches the child domain

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Date:   Tue, 2 May 2017 16:52:24 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Rik van Riel <riel@...hat.com>
Cc:     mingo@...nel.org, lvenanci@...hat.com, lwang@...hat.com,
        efault@....de, tglx@...utronix.de, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 06/14] sched/topology,debug: Verify the first group
 matches the child domain

On Mon, May 01, 2017 at 05:13:26PM -0400, Rik van Riel wrote:
> On Fri, 2017-04-28 at 15:20 +0200, Peter Zijlstra wrote:
> > Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> 
> This could use a changelog.

Yes indeed... I put off writing one because $hard, and clearly I forgot
entirely :-/

How's this?

---
Subject: sched/topology,debug: Verify the first group matches the child domain
From: Peter Zijlstra <peterz@...radead.org>
Date: Fri Apr 14 18:20:48 CEST 2017

We want sched_groups to be sibling child domains (or individual CPUs
when there are no child domains). Furthermore, since the first group
of a domain should include the CPU of that domain, the first group of
each domain should match the child domain.

Verify this is indeed so.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 kernel/sched/topology.c |    6 ++++++
 1 file changed, 6 insertions(+)

--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -93,6 +93,12 @@ static int sched_domain_debug_one(struct
 				group->sgc->capacity);
 		}
 
+		if (group == sd->groups && sd->child &&
+		    !cpumask_equal(sched_domain_span(sd->child),
+				   sched_group_cpus(group))) {
+			printk(KERN_ERR "ERROR: domain->groups does not match domain->child\n");
+		}
+
 		group = group->next;
 
 		if (group != sd->groups)