linux-kernel - [tip:sched/urgent] sched/fair: Fix the min_vruntime update logic in dequeue

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Message-ID: <tip-9845c49cc9bbb317a0bc9e9cf78d8e09d54c9af0@git.kernel.org>
Date:   Tue, 16 Oct 2018 02:15:50 -0700
From:   tip-bot for Song Muchun <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     peterz@...radead.org, linux-kernel@...r.kernel.org,
        torvalds@...ux-foundation.org, tglx@...utronix.de, hpa@...or.com,
        smuchun@...il.com, mingo@...nel.org, efault@....de
Subject: [tip:sched/urgent] sched/fair: Fix the min_vruntime update logic in
 dequeue_entity()

Commit-ID:  9845c49cc9bbb317a0bc9e9cf78d8e09d54c9af0
Gitweb:     https://git.kernel.org/tip/9845c49cc9bbb317a0bc9e9cf78d8e09d54c9af0
Author:     Song Muchun <smuchun@...il.com>
AuthorDate: Sun, 14 Oct 2018 19:26:12 +0800
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Tue, 16 Oct 2018 09:36:01 +0200

sched/fair: Fix the min_vruntime update logic in dequeue_entity()

The comment and the code around the update_min_vruntime() call in
dequeue_entity() are not in agreement.

>From commit:

  b60205c7c558 ("sched/fair: Fix min_vruntime tracking")

I think that we want to update min_vruntime when a task is sleeping/migrating.
So, the check is inverted there - fix it.

Signed-off-by: Song Muchun <smuchun@...il.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Mike Galbraith <efault@....de>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Fixes: b60205c7c558 ("sched/fair: Fix min_vruntime tracking")
Link: http://lkml.kernel.org/r/20181014112612.2614-1-smuchun@gmail.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 kernel/sched/fair.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index f88e00705b55..908c9cdae2f0 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4001,7 +4001,7 @@ dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
 	 * put back on, and if we advance min_vruntime, we'll be placed back
 	 * further than we started -- ie. we'll be penalized.
 	 */
-	if ((flags & (DEQUEUE_SAVE | DEQUEUE_MOVE)) == DEQUEUE_SAVE)
+	if ((flags & (DEQUEUE_SAVE | DEQUEUE_MOVE)) != DEQUEUE_SAVE)
 		update_min_vruntime(cfs_rq);
 }