sched_ext: switch class when preempted by higher priority scheduler

[ Upstream commit 68e449d ]

ops.cpu_release() function, if defined, must be invoked when preempted by
a higher priority scheduler class task. This scenario was skipped in
commit f422316 ("sched_ext: Remove switch_class_scx()"). Let's fix
it.

Fixes: f422316 ("sched_ext: Remove switch_class_scx()")
Signed-off-by: Honglei Wang <[email protected]>
Acked-by: Andrea Righi <[email protected]>
Signed-off-by: Tejun Heo <[email protected]>
Signed-off-by: Sasha Levin <[email protected]>

Author: redsky110

kernel/sched/ext.c

@@ -2917,7 +2917,7 @@ static void put_prev_task_scx(struct rq *rq, struct task_struct *p,
 		 */
 		if (p->scx.slice && !scx_rq_bypassing(rq)) {
 			dispatch_enqueue(&rq->scx.local_dsq, p, SCX_ENQ_HEAD);
-			return;
+			goto switch_class;
 		}
 
 		/*
@@ -2934,6 +2934,7 @@ static void put_prev_task_scx(struct rq *rq, struct task_struct *p,
 		}
 	}
 
+switch_class:
 	if (next && next->sched_class != &ext_sched_class)
 		switch_class(rq, next);
 }