sched: simplify sched_class::yield_task()

the 'p' (task_struct) parameter in the sched_class :: yield_task() is
redundant as the caller is always the 'current'. Get rid of it.

   text    data     bss     dec     hex filename
  24341    2734      20   27095    69d7 sched.o.before
  24330    2734      20   27084    69cc sched.o.after

Signed-off-by: Dmitry Adamushko <dmitry.adamushko@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>

include/linux/sched.h

@@ -858,7 +858,7 @@ struct sched_class {
 
 	void (*enqueue_task) (struct rq *rq, struct task_struct *p, int wakeup);
 	void (*dequeue_task) (struct rq *rq, struct task_struct *p, int sleep);
-	void (*yield_task) (struct rq *rq, struct task_struct *p);
+	void (*yield_task) (struct rq *rq);
 
 	void (*check_preempt_curr) (struct rq *rq, struct task_struct *p);
 

kernel/sched.c

@@ -4537,7 +4537,7 @@ asmlinkage long sys_sched_yield(void)
 	struct rq *rq = this_rq_lock();
 
 	schedstat_inc(rq, yld_cnt);
-	current->sched_class->yield_task(rq, current);
+	current->sched_class->yield_task(rq);
 
 	/*
 	 * Since we are going to call schedule() anyway, there's

kernel/sched_fair.c

@@ -722,11 +722,11 @@ static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int sleep)
  *
  * If compat_yield is turned on then we requeue to the end of the tree.
  */
-static void yield_task_fair(struct rq *rq, struct task_struct *p)
+static void yield_task_fair(struct rq *rq)
 {
-	struct cfs_rq *cfs_rq = task_cfs_rq(p);
+	struct cfs_rq *cfs_rq = &rq->cfs;
 	struct rb_node **link = &cfs_rq->tasks_timeline.rb_node;
-	struct sched_entity *rightmost, *se = &p->se;
+	struct sched_entity *rightmost, *se = &rq->curr->se;
 	struct rb_node *parent;
 
 	/*
@@ -741,8 +741,8 @@ static void yield_task_fair(struct rq *rq, struct task_struct *p)
 		 * Dequeue and enqueue the task to update its
 		 * position within the tree:
 		 */
-		dequeue_entity(cfs_rq, &p->se, 0);
+		dequeue_entity(cfs_rq, se, 0);
-		enqueue_entity(cfs_rq, &p->se, 0);
+		enqueue_entity(cfs_rq, se, 0);
 
 		return;
 	}

kernel/sched_rt.c

@@ -59,9 +59,9 @@ static void requeue_task_rt(struct rq *rq, struct task_struct *p)
 }
 
 static void
-yield_task_rt(struct rq *rq, struct task_struct *p)
+yield_task_rt(struct rq *rq)
 {
-	requeue_task_rt(rq, p);
+	requeue_task_rt(rq, rq->curr);
 }
 
 /*