sched/fair: Fix sched_can_stop_tick() for fair tasks

We can't stop the tick of a rq if there are at least 2 tasks enqueued in
the whole hierarchy and not only at the root cfs rq.

rq->cfs.nr_running tracks the number of sched_entity at one level
whereas rq->cfs.h_nr_running tracks all queued tasks in the
hierarchy.

Fixes: 11cc374 ("sched_ext: Simplify scx_can_stop_tick() invocation in sched_can_stop_tick()")
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Link: https://lore.kernel.org/r/20241202174606.4074512-2-vincent.guittot@linaro.org

Author: vingu-linaro

kernel/sched/core.c

@@ -1341,7 +1341,7 @@ bool sched_can_stop_tick(struct rq *rq)
 	if (scx_enabled() && !scx_can_stop_tick(rq))
 		return false;
 
-	if (rq->cfs.nr_running > 1)
+	if (rq->cfs.h_nr_running > 1)
 		return false;
 
 	/*