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 5.9-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_f.patch and it can be found in the queue-5.9 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit f6cdb95dde5ba6b04d7c89a121d1f041c4806baa Author: Quentin Perret <qperret@xxxxxxxxxx> Date: Thu Nov 12 11:12:01 2020 +0000 sched/fair: Fix overutilized update in enqueue_task_fair() [ Upstream commit 8e1ac4299a6e8726de42310d9c1379f188140c71 ] 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: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 48a6d442b4443..c0c4d9ad7da8e 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -5473,6 +5473,7 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags) 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 @@ -5545,7 +5546,7 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags) * 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); enqueue_throttle: