sched: RT-balance, replace hooks with pre/post schedule and wakeup methods

To make the main sched.c code more agnostic to the schedule classes.
Instead of having specific hooks in the schedule code for the RT class
balancing. They are replaced with a pre_schedule, post_schedule
and task_wake_up methods. These methods may be used by any of the classes
but currently, only the sched_rt class implements them.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

include/linux/sched.h

@@ -843,6 +843,9 @@ struct sched_class {
 	int (*move_one_task) (struct rq *this_rq, int this_cpu,
 			      struct rq *busiest, struct sched_domain *sd,
 			      enum cpu_idle_type idle);
+	void (*pre_schedule) (struct rq *this_rq, struct task_struct *task);
+	void (*post_schedule) (struct rq *this_rq);
+	void (*task_wake_up) (struct rq *this_rq, struct task_struct *task);
 #endif
 
 	void (*set_curr_task) (struct rq *rq);

kernel/sched.c

@@ -1625,7 +1625,10 @@ static int try_to_wake_up(struct task_struct *p, unsigned int state, int sync)
 
 out_running:
 	p->state = TASK_RUNNING;
-	wakeup_balance_rt(rq, p);
+#ifdef CONFIG_SMP
+	if (p->sched_class->task_wake_up)
+		p->sched_class->task_wake_up(rq, p);
+#endif
 out:
 	task_rq_unlock(rq, &flags);
 
@@ -1748,7 +1751,10 @@ void fastcall wake_up_new_task(struct task_struct *p, unsigned long clone_flags)
 		inc_nr_running(p, rq);
 	}
 	check_preempt_curr(rq, p);
-	wakeup_balance_rt(rq, p);
+#ifdef CONFIG_SMP
+	if (p->sched_class->task_wake_up)
+		p->sched_class->task_wake_up(rq, p);
+#endif
 	task_rq_unlock(rq, &flags);
 }
 
@@ -1869,7 +1875,10 @@ static void finish_task_switch(struct rq *rq, struct task_struct *prev)
 	prev_state = prev->state;
 	finish_arch_switch(prev);
 	finish_lock_switch(rq, prev);
-	schedule_tail_balance_rt(rq);
+#ifdef CONFIG_SMP
+	if (current->sched_class->post_schedule)
+		current->sched_class->post_schedule(rq);
+#endif
 
 	fire_sched_in_preempt_notifiers(current);
 	if (mm)
@@ -3638,7 +3647,10 @@ asmlinkage void __sched schedule(void)
 		switch_count = &prev->nvcsw;
 	}
 
-	schedule_balance_rt(rq, prev);
+#ifdef CONFIG_SMP
+	if (prev->sched_class->pre_schedule)
+		prev->sched_class->pre_schedule(rq, prev);
+#endif
 
 	if (unlikely(!rq->nr_running))
 		idle_balance(cpu, rq);

kernel/sched_rt.c

@@ -689,14 +689,14 @@ static int pull_rt_task(struct rq *this_rq)
 	return ret;
 }
 
-static void schedule_balance_rt(struct rq *rq, struct task_struct *prev)
+static void pre_schedule_rt(struct rq *rq, struct task_struct *prev)
 {
 	/* Try to pull RT tasks here if we lower this rq's prio */
 	if (unlikely(rt_task(prev)) && rq->rt.highest_prio > prev->prio)
 		pull_rt_task(rq);
 }
 
-static void schedule_tail_balance_rt(struct rq *rq)
+static void post_schedule_rt(struct rq *rq)
 {
 	/*
 	 * If we have more than one rt_task queued, then
@@ -713,10 +713,9 @@ static void schedule_tail_balance_rt(struct rq *rq)
 }
 
 
-static void wakeup_balance_rt(struct rq *rq, struct task_struct *p)
+static void task_wake_up_rt(struct rq *rq, struct task_struct *p)
 {
-	if (unlikely(rt_task(p)) &&
-	    !task_running(rq, p) &&
+	if (!task_running(rq, p) &&
 	    (p->prio >= rq->rt.highest_prio) &&
 	    rq->rt.overloaded)
 		push_rt_tasks(rq);
@@ -780,11 +779,6 @@ static void leave_domain_rt(struct rq *rq)
 	if (rq->rt.overloaded)
 		rt_clear_overload(rq);
 }
-
-#else /* CONFIG_SMP */
-# define schedule_tail_balance_rt(rq)	do { } while (0)
-# define schedule_balance_rt(rq, prev)	do { } while (0)
-# define wakeup_balance_rt(rq, p)	do { } while (0)
 #endif /* CONFIG_SMP */
 
 static void task_tick_rt(struct rq *rq, struct task_struct *p)
@@ -840,6 +834,9 @@ const struct sched_class rt_sched_class = {
 	.set_cpus_allowed       = set_cpus_allowed_rt,
 	.join_domain            = join_domain_rt,
 	.leave_domain           = leave_domain_rt,
+	.pre_schedule		= pre_schedule_rt,
+	.post_schedule		= post_schedule_rt,
+	.task_wake_up		= task_wake_up_rt,
 #endif
 
 	.set_curr_task          = set_curr_task_rt,