sched: Add put_prev_task(.next)

In order to tell the previous sched_class what the next task is, add
put_prev_task(.next).

Notable SCX will use this to:

 1) determine the next task will leave the SCX sched class and push
    the current task to another CPU if possible.
 2) statistics on how often and which other classes preempt it

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20240813224016.367421076@infradead.org

1 files changed, 3 insertions, 3 deletions

diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 2a216c9153e9..3744f16a1293 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -2314,7 +2314,7 @@ struct sched_class {
 	 */
 	struct task_struct *(*pick_next_task)(struct rq *rq, struct task_struct *prev);
 
-	void (*put_prev_task)(struct rq *rq, struct task_struct *p);
+	void (*put_prev_task)(struct rq *rq, struct task_struct *p, struct task_struct *next);
 	void (*set_next_task)(struct rq *rq, struct task_struct *p, bool first);
 
 #ifdef CONFIG_SMP
@@ -2364,7 +2364,7 @@ struct sched_class {
 static inline void put_prev_task(struct rq *rq, struct task_struct *prev)
 {
 	WARN_ON_ONCE(rq->curr != prev);
-	prev->sched_class->put_prev_task(rq, prev);
+	prev->sched_class->put_prev_task(rq, prev, NULL);
 }
 
 static inline void set_next_task(struct rq *rq, struct task_struct *next)
@@ -2393,7 +2393,7 @@ static inline void put_prev_set_next_task(struct rq *rq,
 	if (next == prev)
 		return;
 
-	prev->sched_class->put_prev_task(rq, prev);
+	prev->sched_class->put_prev_task(rq, prev, next);
 	next->sched_class->set_next_task(rq, next, true);
 }