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>

3 files changed, 26 insertions, 14 deletions

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 2e69f19369e4..c67d2c2f0111 100644
--- a/include/linux/sched.h
+++ b/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);
diff --git a/kernel/sched.c b/kernel/sched.c
index 9d6fb731559b..2368a0d882e3 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -1625,7 +1625,10 @@ out_activate:
 
 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 @@ need_resched_nonpreemptible:
                 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);
diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c
index 3ea0cae513d2..a5a45104603a 100644
--- a/kernel/sched_rt.c
+++ b/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,