sched: rework enqueue/dequeue_entity() to get rid of set_curr_task()

rework enqueue/dequeue_entity() to get rid of 
sched_class::set_curr_task(). This simplifies sched_setscheduler(), 
rt_mutex_setprio() and sched_move_tasks().

   text    data     bss     dec     hex filename
  24330    2734      20   27084    69cc sched.o.before
  24233    2730      20   26983    6967 sched.o.after

Signed-off-by: Dmitry Adamushko <dmitry.adamushko@gmail.com>
Signed-off-by: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.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>

5 files changed, 35 insertions, 67 deletions

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 66169005f008..abcb02738d95 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -871,7 +871,6 @@ struct sched_class {
                         struct sched_domain *sd, enum cpu_idle_type idle,
                         int *all_pinned, int *this_best_prio);
 
-        void (*set_curr_task) (struct rq *rq);
         void (*task_tick) (struct rq *rq, struct task_struct *p);
         void (*task_new) (struct rq *rq, struct task_struct *p);
 };
diff --git a/kernel/sched.c b/kernel/sched.c
index e1f784f4b4db..72c936d3e332 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -3915,8 +3915,8 @@ EXPORT_SYMBOL(sleep_on_timeout);
  */
 void rt_mutex_setprio(struct task_struct *p, int prio)
 {
-        int oldprio, on_rq, running;
         unsigned long flags;
+        int oldprio, on_rq;
         struct rq *rq;
 
         BUG_ON(prio < 0 || prio > MAX_PRIO);
@@ -3926,12 +3926,8 @@ void rt_mutex_setprio(struct task_struct *p, int prio)
 
         oldprio = p->prio;
         on_rq = p->se.on_rq;
-        running = task_running(rq, p);
-        if (on_rq) {
+        if (on_rq)
                 dequeue_task(rq, p, 0);
-                if (running)
-                        p->sched_class->put_prev_task(rq, p);
-        }
 
         if (rt_prio(prio))
                 p->sched_class = &rt_sched_class;
@@ -3941,15 +3937,13 @@ void rt_mutex_setprio(struct task_struct *p, int prio)
         p->prio = prio;
 
         if (on_rq) {
-                if (running)
-                        p->sched_class->set_curr_task(rq);
                 enqueue_task(rq, p, 0);
                 /*
                  * Reschedule if we are currently running on this runqueue and
                  * our priority decreased, or if we are not currently running on
                  * this runqueue and our priority is higher than the current's
                  */
-                if (running) {
+                if (task_running(rq, p)) {
                         if (p->prio > oldprio)
                                 resched_task(rq->curr);
                 } else {
@@ -4155,7 +4149,7 @@ __setscheduler(struct rq *rq, struct task_struct *p, int policy, int prio)
 int sched_setscheduler(struct task_struct *p, int policy,
                        struct sched_param *param)
 {
-        int retval, oldprio, oldpolicy = -1, on_rq, running;
+        int retval, oldprio, oldpolicy = -1, on_rq;
         unsigned long flags;
         struct rq *rq;
 
@@ -4237,24 +4231,20 @@ recheck:
         }
         update_rq_clock(rq);
         on_rq = p->se.on_rq;
-        running = task_running(rq, p);
-        if (on_rq) {
+        if (on_rq)
                 deactivate_task(rq, p, 0);
-                if (running)
-                        p->sched_class->put_prev_task(rq, p);
-        }
+
         oldprio = p->prio;
         __setscheduler(rq, p, policy, param->sched_priority);
+
         if (on_rq) {
-                if (running)
-                        p->sched_class->set_curr_task(rq);
                 activate_task(rq, p, 0);
                 /*
                  * Reschedule if we are currently running on this runqueue and
                  * our priority decreased, or if we are not currently running on
                  * this runqueue and our priority is higher than the current's
                  */
-                if (running) {
+                if (task_running(rq, p)) {
                         if (p->prio > oldprio)
                                 resched_task(rq->curr);
                 } else {
@@ -6855,19 +6845,13 @@ static void sched_move_task(struct container_subsys *ss, struct container *cont,
         running = task_running(rq, tsk);
         on_rq = tsk->se.on_rq;
 
-        if (on_rq) {
+        if (on_rq)
                 dequeue_task(rq, tsk, 0);
-                if (unlikely(running))
-                        tsk->sched_class->put_prev_task(rq, tsk);
-        }
 
         set_task_cfs_rq(tsk);
 
-        if (on_rq) {
-                if (unlikely(running))
-                        tsk->sched_class->set_curr_task(rq);
+        if (on_rq)
                 enqueue_task(rq, tsk, 0);
-        }
 
 done:
         task_rq_unlock(rq, &flags);
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index 4dd256d46853..568e922255c6 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -472,9 +472,20 @@ place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
 }
 
 static void
-enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int wakeup)
+enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
+                int wakeup, int set_curr)
 {
         /*
+         * In case of the 'current'.
+         */
+        if (unlikely(set_curr)) {
+                update_stats_curr_start(cfs_rq, se);
+                cfs_rq->curr = se;
+                account_entity_enqueue(cfs_rq, se);
+                return;
+        }
+
+        /*
          * Update the fair clock.
          */
         update_curr(cfs_rq);
@@ -485,8 +496,7 @@ enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int wakeup)
         }
 
         update_stats_enqueue(cfs_rq, se);
-        if (se != cfs_rq->curr)
-                __enqueue_entity(cfs_rq, se);
+        __enqueue_entity(cfs_rq, se);
         account_entity_enqueue(cfs_rq, se);
 }
 
@@ -506,8 +516,12 @@ dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int sleep)
                 }
         }
 #endif
-        if (se != cfs_rq->curr)
+        if (likely(se != cfs_rq->curr))
                 __dequeue_entity(cfs_rq, se);
+        else {
+                update_stats_curr_end(cfs_rq, se);
+                cfs_rq->curr = NULL;
+        }
         account_entity_dequeue(cfs_rq, se);
 }
 
@@ -689,12 +703,17 @@ static void enqueue_task_fair(struct rq *rq, struct task_struct *p, int wakeup)
 {
         struct cfs_rq *cfs_rq;
         struct sched_entity *se = &p->se;
+        int set_curr = 0;
+
+        /* Are we enqueuing the current task? */
+        if (unlikely(task_running(rq, p)))
+                set_curr = 1;
 
         for_each_sched_entity(se) {
                 if (se->on_rq)
                         break;
                 cfs_rq = cfs_rq_of(se);
-                enqueue_entity(cfs_rq, se, wakeup);
+                enqueue_entity(cfs_rq, se, wakeup, set_curr);
         }
 }
 
@@ -742,7 +761,7 @@ static void yield_task_fair(struct rq *rq)
                  * position within the tree:
                  */
                 dequeue_entity(cfs_rq, se, 0);
-                enqueue_entity(cfs_rq, se, 0);
+                enqueue_entity(cfs_rq, se, 0, 1);
 
                 return;
         }
@@ -985,29 +1004,6 @@ static void task_new_fair(struct rq *rq, struct task_struct *p)
         resched_task(rq->curr);
 }
 
-#ifdef CONFIG_FAIR_GROUP_SCHED
-/* Account for a task changing its policy or group.
- *
- * This routine is mostly called to set cfs_rq->curr field when a task
- * migrates between groups/classes.
- */
-static void set_curr_task_fair(struct rq *rq)
-{
-        struct sched_entity *se = &rq->curr->se;
-
-        for_each_sched_entity(se)
-                set_next_entity(cfs_rq_of(se), se);
-}
-#else
-static void set_curr_task_fair(struct rq *rq)
-{
-        struct sched_entity *se = &rq->curr->se;
-        struct cfs_rq *cfs_rq = cfs_rq_of(se);
-
-        cfs_rq->curr = se;
-}
-#endif
-
 /*
  * All the scheduling class methods:
  */
@@ -1023,7 +1019,6 @@ struct sched_class fair_sched_class __read_mostly = {
 
         .load_balance           = load_balance_fair,
 
-        .set_curr_task          = set_curr_task_fair,
         .task_tick              = task_tick_fair,
         .task_new               = task_new_fair,
 };
diff --git a/kernel/sched_idletask.c b/kernel/sched_idletask.c
index 5ebf829cdd73..3503fb2d9f96 100644
--- a/kernel/sched_idletask.c
+++ b/kernel/sched_idletask.c
@@ -50,10 +50,6 @@ static void task_tick_idle(struct rq *rq, struct task_struct *curr)
 {
 }
 
-static void set_curr_task_idle(struct rq *rq)
-{
-}
-
 /*
  * Simple, special scheduling class for the per-CPU idle tasks:
  */
@@ -70,7 +66,6 @@ static struct sched_class idle_sched_class __read_mostly = {
 
         .load_balance           = load_balance_idle,
 
-        .set_curr_task          = set_curr_task_idle,
         .task_tick              = task_tick_idle,
         /* no .task_new for idle tasks */
 };
diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c
index b86944c20f9f..3c77c03bdf1e 100644
--- a/kernel/sched_rt.c
+++ b/kernel/sched_rt.c
@@ -218,10 +218,6 @@ static void task_tick_rt(struct rq *rq, struct task_struct *p)
         }
 }
 
-static void set_curr_task_rt(struct rq *rq)
-{
-}
-
 static struct sched_class rt_sched_class __read_mostly = {
         .enqueue_task           = enqueue_task_rt,
         .dequeue_task           = dequeue_task_rt,
@@ -234,6 +230,5 @@ static struct sched_class rt_sched_class __read_mostly = {
 
         .load_balance           = load_balance_rt,
 
-        .set_curr_task          = set_curr_task_rt,
         .task_tick              = task_tick_rt,
 };