linux-kernel - [PATCH 3.16 182/204] sched/topology: Simplify build_overlap_sched

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Date:   Thu, 28 Dec 2017 17:05:44 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Mike Galbraith" <efault@....de>,
        "Ingo Molnar" <mingo@...nel.org>,
        "Thomas Gleixner" <tglx@...utronix.de>,
        "Linus Torvalds" <torvalds@...ux-foundation.org>,
        "Peter Zijlstra" <peterz@...radead.org>
Subject: [PATCH 3.16 182/204] sched/topology: Simplify build_overlap_sched_groups()

3.16.52-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Peter Zijlstra <peterz@...radead.org>

commit 91eaed0d61319f58a9f8e43d41a8cbb069b4f73d upstream.

Now that the first group will always be the previous domain of this
@cpu this can be simplified.

In fact, writing the code now removed should've been a big clue I was
doing it wrong :/

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Mike Galbraith <efault@....de>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: linux-kernel@...r.kernel.org
Signed-off-by: Ingo Molnar <mingo@...nel.org>
[bwh: Backported to 3.16: adjust filename, context]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 kernel/sched/core.c | 13 ++-----------
 1 file changed, 2 insertions(+), 11 deletions(-)

--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5869,7 +5869,7 @@ static void init_overlap_sched_group(str
 static int
 build_overlap_sched_groups(struct sched_domain *sd, int cpu)
 {
-	struct sched_group *first = NULL, *last = NULL, *groups = NULL, *sg;
+	struct sched_group *first = NULL, *last = NULL, *sg;
 	const struct cpumask *span = sched_domain_span(sd);
 	struct cpumask *covered = sched_domains_tmpmask;
 	struct sd_data *sdd = sd->private;
@@ -5899,15 +5899,6 @@ build_overlap_sched_groups(struct sched_
 
 		init_overlap_sched_group(sd, sg);
 
-		/*
-		 * Make sure the first group of this domain contains the
-		 * canonical balance cpu. Otherwise the sched_domain iteration
-		 * breaks. See update_sg_lb_stats().
-		 */
-		if ((!groups && cpumask_test_cpu(cpu, sg_span)) ||
-		    group_balance_cpu(sg) == cpu)
-			groups = sg;
-
 		if (!first)
 			first = sg;
 		if (last)
@@ -5915,7 +5906,7 @@ build_overlap_sched_groups(struct sched_
 		last = sg;
 		last->next = first;
 	}
-	sd->groups = groups;
+	sd->groups = first;
 
 	return 0;