sched: mark scheduling classes as const

mark scheduling classes as const. The speeds up the code
a bit and shrinks it:

   text    data     bss     dec     hex filename
  40027    4018     292   44337    ad31 sched.o.before
  40190    3842     292   44324    ad24 sched.o.after

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>

4 files changed, 11 insertions, 17 deletions

diff --git a/kernel/sched.c b/kernel/sched.c
index e1657e0c86d0..f582e2cedb09 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -847,9 +847,9 @@ static int balance_tasks(struct rq *this_rq, int this_cpu, struct rq *busiest,
                       int *this_best_prio, struct rq_iterator *iterator);
 
 #include "sched_stats.h"
-#include "sched_rt.c"
-#include "sched_fair.c"
 #include "sched_idletask.c"
+#include "sched_fair.c"
+#include "sched_rt.c"
 #ifdef CONFIG_SCHED_DEBUG
 # include "sched_debug.c"
 #endif
@@ -2251,7 +2251,7 @@ static int move_tasks(struct rq *this_rq, int this_cpu, struct rq *busiest,
                       struct sched_domain *sd, enum cpu_idle_type idle,
                       int *all_pinned)
 {
-        struct sched_class *class = sched_class_highest;
+        const struct sched_class *class = sched_class_highest;
         unsigned long total_load_moved = 0;
         int this_best_prio = this_rq->curr->prio;
 
@@ -2276,7 +2276,7 @@ static int move_tasks(struct rq *this_rq, int this_cpu, struct rq *busiest,
 static int move_one_task(struct rq *this_rq, int this_cpu, struct rq *busiest,
                          struct sched_domain *sd, enum cpu_idle_type idle)
 {
-        struct sched_class *class;
+        const struct sched_class *class;
         int this_best_prio = MAX_PRIO;
 
         for (class = sched_class_highest; class; class = class->next)
@@ -3432,7 +3432,7 @@ static inline void schedule_debug(struct task_struct *prev)
 static inline struct task_struct *
 pick_next_task(struct rq *rq, struct task_struct *prev)
 {
-        struct sched_class *class;
+        const struct sched_class *class;
         struct task_struct *p;
 
         /*
@@ -6504,13 +6504,6 @@ void __init sched_init(void)
         int highest_cpu = 0;
         int i, j;
 
-        /*
-         * Link up the scheduling class hierarchy:
-         */
-        rt_sched_class.next = &fair_sched_class;
-        fair_sched_class.next = &idle_sched_class;
-        idle_sched_class.next = NULL;
-
         for_each_possible_cpu(i) {
                 struct rt_prio_array *array;
                 struct rq *rq;
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index de13a6f5b977..32fd976f8566 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -76,8 +76,6 @@ const_debug unsigned int sysctl_sched_batch_wakeup_granularity = 25000000UL;
  */
 const_debug unsigned int sysctl_sched_wakeup_granularity = 2000000UL;
 
-extern struct sched_class fair_sched_class;
-
 /**************************************************************
  * CFS operations on generic schedulable entities:
  */
@@ -1031,7 +1029,8 @@ static void set_curr_task_fair(struct rq *rq)
 /*
  * All the scheduling class methods:
  */
-struct sched_class fair_sched_class __read_mostly = {
+static const struct sched_class fair_sched_class = {
+        .next                   = &idle_sched_class,
         .enqueue_task           = enqueue_task_fair,
         .dequeue_task           = dequeue_task_fair,
         .yield_task             = yield_task_fair,
diff --git a/kernel/sched_idletask.c b/kernel/sched_idletask.c
index 5ebf829cdd73..6e2ead41516e 100644
--- a/kernel/sched_idletask.c
+++ b/kernel/sched_idletask.c
@@ -57,7 +57,8 @@ static void set_curr_task_idle(struct rq *rq)
 /*
  * Simple, special scheduling class for the per-CPU idle tasks:
  */
-static struct sched_class idle_sched_class __read_mostly = {
+const struct sched_class idle_sched_class = {
+        /* .next is NULL */
         /* no enqueue/yield_task for idle tasks */
 
         /* dequeue is not valid, we print a debug message there: */
diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c
index e1d5f1c8b532..dbe4d8cf80d6 100644
--- a/kernel/sched_rt.c
+++ b/kernel/sched_rt.c
@@ -225,7 +225,8 @@ static void set_curr_task_rt(struct rq *rq)
         p->se.exec_start = rq->clock;
 }
 
-static struct sched_class rt_sched_class __read_mostly = {
+const struct sched_class rt_sched_class = {
+        .next                   = &fair_sched_class,
         .enqueue_task           = enqueue_task_rt,
         .dequeue_task           = dequeue_task_rt,
         .yield_task             = yield_task_rt,