We should not (re)set slice protection in the sched_change pattern
which calls put_prev_task() / set_next_task().

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
 kernel/sched/fair.c |   11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5420,7 +5420,7 @@ dequeue_entity(struct cfs_rq *cfs_rq, st
 }
 
 static void
-set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
+set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, bool first)
 {
 	clear_buddies(cfs_rq, se);
 
@@ -5435,7 +5435,8 @@ set_next_entity(struct cfs_rq *cfs_rq, s
 		__dequeue_entity(cfs_rq, se);
 		update_load_avg(cfs_rq, se, UPDATE_TG);
 
-		set_protect_slice(cfs_rq, se);
+		if (first)
+			set_protect_slice(cfs_rq, se);
 	}
 
 	update_stats_curr_start(cfs_rq, se);
@@ -8958,13 +8959,13 @@ pick_next_task_fair(struct rq *rq, struc
 				pse = parent_entity(pse);
 			}
 			if (se_depth >= pse_depth) {
-				set_next_entity(cfs_rq_of(se), se);
+				set_next_entity(cfs_rq_of(se), se, true);
 				se = parent_entity(se);
 			}
 		}
 
 		put_prev_entity(cfs_rq, pse);
-		set_next_entity(cfs_rq, se);
+		set_next_entity(cfs_rq, se, true);
 
 		__set_next_task_fair(rq, p, true);
 	}
@@ -13578,7 +13579,7 @@ static void set_next_task_fair(struct rq
 	for_each_sched_entity(se) {
 		struct cfs_rq *cfs_rq = cfs_rq_of(se);
 
-		set_next_entity(cfs_rq, se);
+		set_next_entity(cfs_rq, se, first);
 		/* ensure bandwidth has been allocated on our new cfs_rq */
 		account_cfs_rq_runtime(cfs_rq, 0);
 	}

On Fri, 30 Jan 2026 at 10:47, Peter Zijlstra <peterz@infradead.org> wrote:
>
> We should not (re)set slice protection in the sched_change pattern
> which calls put_prev_task() / set_next_task().
>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>

Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>

> ---
>  kernel/sched/fair.c |   11 ++++++-----
>  1 file changed, 6 insertions(+), 5 deletions(-)
>
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -5420,7 +5420,7 @@ dequeue_entity(struct cfs_rq *cfs_rq, st
>  }
>
>  static void
> -set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
> +set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, bool first)
>  {
>         clear_buddies(cfs_rq, se);
>
> @@ -5435,7 +5435,8 @@ set_next_entity(struct cfs_rq *cfs_rq, s
>                 __dequeue_entity(cfs_rq, se);
>                 update_load_avg(cfs_rq, se, UPDATE_TG);
>
> -               set_protect_slice(cfs_rq, se);
> +               if (first)
> +                       set_protect_slice(cfs_rq, se);
>         }
>
>         update_stats_curr_start(cfs_rq, se);
> @@ -8958,13 +8959,13 @@ pick_next_task_fair(struct rq *rq, struc
>                                 pse = parent_entity(pse);
>                         }
>                         if (se_depth >= pse_depth) {
> -                               set_next_entity(cfs_rq_of(se), se);
> +                               set_next_entity(cfs_rq_of(se), se, true);
>                                 se = parent_entity(se);
>                         }
>                 }
>
>                 put_prev_entity(cfs_rq, pse);
> -               set_next_entity(cfs_rq, se);
> +               set_next_entity(cfs_rq, se, true);
>
>                 __set_next_task_fair(rq, p, true);
>         }
> @@ -13578,7 +13579,7 @@ static void set_next_task_fair(struct rq
>         for_each_sched_entity(se) {
>                 struct cfs_rq *cfs_rq = cfs_rq_of(se);
>
> -               set_next_entity(cfs_rq, se);
> +               set_next_entity(cfs_rq, se, first);
>                 /* ensure bandwidth has been allocated on our new cfs_rq */
>                 account_cfs_rq_runtime(cfs_rq, 0);
>         }
>
>