sched/fair: Only set slice protection at pick time

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

Fixes: 63304558ba5d ("sched/eevdf: Curb wakeup-preemption")
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Tested-by: K Prateek Nayak <kprateek.nayak@amd.com>
Tested-by: Shubhang Kaushik <shubhang@os.amperecomputing.com>
Link: https://patch.msgid.link/20260219080624.561421378%40infradead.org

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 56dddd4fd20893a764049096b7e9ff3af99bbbf3..f2b46c33a8c5521ad1f24f66cec3d9f3fa86db0b 100644 (file)
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5445,7 +5445,7 @@ dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
 }
 
 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);
 
@@ -5460,7 +5460,8 @@ set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
                __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);
@@ -8978,13 +8979,13 @@ again:
                                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);
        }
@@ -13598,7 +13599,7 @@ static void set_next_task_fair(struct rq *rq, struct task_struct *p, bool first)
        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);
        }