sched/eevdf: Fixup PELT vs DELAYED_DEQUEUE

Note that tasks that are kept on the runqueue to burn off negative
lag, are not in fact runnable anymore, they'll get dequeued the moment
they get picked.

As such, don't count this time towards runnable.

Thanks to Valentin for spotting I had this backwards initially.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <vschneid@redhat.com>
Tested-by: Valentin Schneider <vschneid@redhat.com>
Link: https://lkml.kernel.org/r/20240727105030.514088302@infradead.org

kernel/sched/fair.c

@@ -5402,6 +5402,7 @@ dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
 		    !entity_eligible(cfs_rq, se)) {
 			if (cfs_rq->next == se)
 				cfs_rq->next = NULL;
+			update_load_avg(cfs_rq, se, 0);
 			se->sched_delayed = 1;
 			return false;
 		}
@@ -6841,6 +6842,7 @@ requeue_delayed_entity(struct sched_entity *se)
 		}
 	}
 
+	update_load_avg(cfs_rq, se, 0);
 	se->sched_delayed = 0;
 }
 

kernel/sched/sched.h

@@ -820,6 +820,9 @@ static inline void se_update_runnable(struct sched_entity *se)
 
 static inline long se_runnable(struct sched_entity *se)
 {
+	if (se->sched_delayed)
+		return false;
+
 	if (entity_is_task(se))
 		return !!se->on_rq;
 	else
@@ -834,6 +837,9 @@ static inline void se_update_runnable(struct sched_entity *se) { }
 
 static inline long se_runnable(struct sched_entity *se)
 {
+	if (se->sched_delayed)
+		return false;
+
 	return !!se->on_rq;
 }