sched: revert recent removal of set_curr_task()

Revert removal of set_curr_task.
Use put_prev_task/set_curr_task when changing groups/policies

Signed-off-by: Srivatsa Vaddagiri < vatsa@linux.vnet.ibm.com>
Signed-off-by: Dhaval Giani <dhaval@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>

5 files changed, 72 insertions, 44 deletions

diff --git a/include/linux/sched.h b/include/linux/sched.h
index abcb02738d95..66169005f008 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -871,6 +871,7 @@ 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 72c936d3e332..ee7ac71b12f8 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -3916,7 +3916,7 @@ EXPORT_SYMBOL(sleep_on_timeout);
 void rt_mutex_setprio(struct task_struct *p, int prio)
 {
         unsigned long flags;
-        int oldprio, on_rq;
+        int oldprio, on_rq, running;
         struct rq *rq;
 
         BUG_ON(prio < 0 || prio > MAX_PRIO);
@@ -3926,8 +3926,12 @@ void rt_mutex_setprio(struct task_struct *p, int prio)
 
         oldprio = p->prio;
         on_rq = p->se.on_rq;
-        if (on_rq)
+        running = task_running(rq, p);
+        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;
@@ -3937,13 +3941,15 @@ 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 (task_running(rq, p)) {
+                if (running) {
                         if (p->prio > oldprio)
                                 resched_task(rq->curr);
                 } else {
@@ -4149,7 +4155,7 @@ __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;
+        int retval, oldprio, oldpolicy = -1, on_rq, running;
         unsigned long flags;
         struct rq *rq;
 
@@ -4231,20 +4237,26 @@ recheck:
         }
         update_rq_clock(rq);
         on_rq = p->se.on_rq;
-        if (on_rq)
+        running = task_running(rq, p);
+        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 (task_running(rq, p)) {
+                if (running) {
                         if (p->prio > oldprio)
                                 resched_task(rq->curr);
                 } else {
@@ -6845,13 +6857,19 @@ 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 (on_rq) {
+                if (unlikely(running))
+                        tsk->sched_class->set_curr_task(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 9f93a5c127e8..92563cd5af75 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -472,20 +472,9 @@ 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, int set_curr)
+enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int wakeup)
 {
         /*
-         * 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);
@@ -496,7 +485,8 @@ enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
         }
 
         update_stats_enqueue(cfs_rq, se);
-        __enqueue_entity(cfs_rq, se);
+        if (se != cfs_rq->curr)
+                __enqueue_entity(cfs_rq, se);
         account_entity_enqueue(cfs_rq, se);
 }
 
@@ -516,12 +506,8 @@ dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int sleep)
                 }
         }
 #endif
-        if (likely(se != cfs_rq->curr))
+        if (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);
 }
 
@@ -539,15 +525,20 @@ check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
                 resched_task(rq_of(cfs_rq)->curr);
 }
 
-static inline void
+static void
 set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
 {
-        /*
-         * Any task has to be enqueued before it get to execute on
-         * a CPU. So account for the time it spent waiting on the
-         * runqueue.
-         */
-        update_stats_wait_end(cfs_rq, se);
+        /* 'current' is not kept within the tree. */
+        if (se->on_rq) {
+                /*
+                 * Any task has to be enqueued before it get to execute on
+                 * a CPU. So account for the time it spent waiting on the
+                 * runqueue.
+                 */
+                update_stats_wait_end(cfs_rq, se);
+                __dequeue_entity(cfs_rq, se);
+        }
+
         update_stats_curr_start(cfs_rq, se);
         cfs_rq->curr = se;
 #ifdef CONFIG_SCHEDSTATS
@@ -568,10 +559,6 @@ static struct sched_entity *pick_next_entity(struct cfs_rq *cfs_rq)
 {
         struct sched_entity *se = __pick_next_entity(cfs_rq);
 
-        /* 'current' is not kept within the tree. */
-        if (se)
-                __dequeue_entity(cfs_rq, se);
-
         set_next_entity(cfs_rq, se);
 
         return se;
@@ -703,17 +690,12 @@ 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, set_curr);
+                enqueue_entity(cfs_rq, se, wakeup);
         }
 }
 
@@ -761,7 +743,7 @@ static void yield_task_fair(struct rq *rq)
                  * position within the tree:
                  */
                 dequeue_entity(cfs_rq, se, 0);
-                enqueue_entity(cfs_rq, se, 0, 1);
+                enqueue_entity(cfs_rq, se, 0);
 
                 return;
         }
@@ -1004,6 +986,19 @@ static void task_new_fair(struct rq *rq, struct task_struct *p)
         resched_task(rq->curr);
 }
 
+/* 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);
+}
+
 /*
  * All the scheduling class methods:
  */
@@ -1019,6 +1014,7 @@ 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 3503fb2d9f96..5ebf829cdd73 100644
--- a/kernel/sched_idletask.c
+++ b/kernel/sched_idletask.c
@@ -50,6 +50,10 @@ 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:
  */
@@ -66,6 +70,7 @@ 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 3c77c03bdf1e..e1d5f1c8b532 100644
--- a/kernel/sched_rt.c
+++ b/kernel/sched_rt.c
@@ -218,6 +218,13 @@ static void task_tick_rt(struct rq *rq, struct task_struct *p)
         }
 }
 
+static void set_curr_task_rt(struct rq *rq)
+{
+        struct task_struct *p = rq->curr;
+
+        p->se.exec_start = rq->clock;
+}
+
 static struct sched_class rt_sched_class __read_mostly = {
         .enqueue_task           = enqueue_task_rt,
         .dequeue_task           = dequeue_task_rt,
@@ -230,5 +237,6 @@ 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,
 };