Patch "sched/fair: Fix overutilized update in enqueue_task_fair()" has been added to the 5.4-stable tree

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This is a note to let you know that I've just added the patch titled

    sched/fair: Fix overutilized update in enqueue_task_fair()

to the 5.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     sched-fair-fix-overutilized-update-in-enqueue_task_fair.patch
and it can be found in the queue-5.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.


>From 8e1ac4299a6e8726de42310d9c1379f188140c71 Mon Sep 17 00:00:00 2001
From: Quentin Perret <qperret@xxxxxxxxxx>
Date: Thu, 12 Nov 2020 11:12:01 +0000
Subject: sched/fair: Fix overutilized update in enqueue_task_fair()

From: Quentin Perret <qperret@xxxxxxxxxx>

commit 8e1ac4299a6e8726de42310d9c1379f188140c71 upstream.

enqueue_task_fair() attempts to skip the overutilized update for new
tasks as their util_avg is not accurate yet. However, the flag we check
to do so is overwritten earlier on in the function, which makes the
condition pretty much a nop.

Fix this by saving the flag early on.

Fixes: 2802bf3cd936 ("sched/fair: Add over-utilization/tipping point indicator")
Reported-by: Rick Yiu <rickyiu@xxxxxxxxxx>
Signed-off-by: Quentin Perret <qperret@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Reviewed-by: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
Reviewed-by: Valentin Schneider <valentin.schneider@xxxxxxx>
Link: https://lkml.kernel.org/r/20201112111201.2081902-1-qperret@xxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 kernel/sched/fair.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5228,6 +5228,7 @@ enqueue_task_fair(struct rq *rq, struct
 	struct cfs_rq *cfs_rq;
 	struct sched_entity *se = &p->se;
 	int idle_h_nr_running = task_has_idle_policy(p);
+	int task_new = !(flags & ENQUEUE_WAKEUP);
 
 	/*
 	 * The code below (indirectly) updates schedutil which looks at
@@ -5299,7 +5300,7 @@ enqueue_throttle:
 		 * into account, but that is not straightforward to implement,
 		 * and the following generally works well enough in practice.
 		 */
-		if (flags & ENQUEUE_WAKEUP)
+		if (!task_new)
 			update_overutilized_status(rq);
 
 	}


Patches currently in stable-queue which might be from qperret@xxxxxxxxxx are

queue-5.4/sched-fair-fix-overutilized-update-in-enqueue_task_fair.patch



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