7 files changed, 28 insertions, 12 deletions

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index fb9764fbc537..49db434a35d0 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -4681,6 +4681,22 @@ static void calc_load_migrate(struct rq *rq)
                 atomic_long_add(delta, &calc_load_tasks);
 }
 
+static void put_prev_task_fake(struct rq *rq, struct task_struct *prev)
+{
+}
+
+static const struct sched_class fake_sched_class = {
+        .put_prev_task = put_prev_task_fake,
+};
+
+static struct task_struct fake_task = {
+        /*
+         * Avoid pull_{rt,dl}_task()
+         */
+        .prio = MAX_PRIO + 1,
+        .sched_class = &fake_sched_class,
+};
+
 /*
  * Migrate all tasks from the rq, sleeping tasks will be migrated by
  * try_to_wake_up()->select_task_rq().
@@ -4721,7 +4737,7 @@ static void migrate_tasks(unsigned int dead_cpu)
                 if (rq->nr_running == 1)
                         break;
 
-                next = pick_next_task(rq, NULL);
+                next = pick_next_task(rq, &fake_task);
                 BUG_ON(!next);
                 next->sched_class->put_prev_task(rq, next);
 
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index ed31ef66ab9d..bfeb84ecc32b 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -1008,8 +1008,7 @@ struct task_struct *pick_next_task_dl(struct rq *rq, struct task_struct *prev)
         if (unlikely(!dl_rq->dl_nr_running))
                 return NULL;
 
-        if (prev)
-                prev->sched_class->put_prev_task(rq, prev);
+        put_prev_task(rq, prev);
 
         dl_se = pick_next_dl_entity(rq, dl_rq);
         BUG_ON(!dl_se);
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 40c758bbdd57..e884e45982af 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4690,7 +4690,7 @@ again:
         if (!cfs_rq->nr_running)
                 goto idle;
 
-        if (!prev || prev->sched_class != &fair_sched_class)
+        if (prev->sched_class != &fair_sched_class)
                 goto simple;
 
         /*
@@ -4766,8 +4766,7 @@ simple:
         if (!cfs_rq->nr_running)
                 goto idle;
 
-        if (prev)
-                prev->sched_class->put_prev_task(rq, prev);
+        put_prev_task(rq, prev);
 
         do {
                 se = pick_next_entity(cfs_rq, NULL);
diff --git a/kernel/sched/idle_task.c b/kernel/sched/idle_task.c
index f7d03af79a5b..53ff9e7c76d2 100644
--- a/kernel/sched/idle_task.c
+++ b/kernel/sched/idle_task.c
@@ -26,8 +26,7 @@ static void check_preempt_curr_idle(struct rq *rq, struct task_struct *p, int fl
 static struct task_struct *
 pick_next_task_idle(struct rq *rq, struct task_struct *prev)
 {
-        if (prev)
-                prev->sched_class->put_prev_task(rq, prev);
+        put_prev_task(rq, prev);
 
         schedstat_inc(rq, sched_goidle);
 #ifdef CONFIG_SMP
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 72f9ec759972..65c2d6881ac3 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -1344,8 +1344,7 @@ pick_next_task_rt(struct rq *rq, struct task_struct *prev)
         if (rt_rq_throttled(rt_rq))
                 return NULL;
 
-        if (prev)
-                prev->sched_class->put_prev_task(rq, prev);
+        put_prev_task(rq, prev);
 
         p = _pick_next_task_rt(rq);
 
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 92018f9821e8..d276147ba5e4 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1147,6 +1147,11 @@ struct sched_class {
 #endif
 };
 
+static inline void put_prev_task(struct rq *rq, struct task_struct *prev)
+{
+        prev->sched_class->put_prev_task(rq, prev);
+}
+
 #define sched_class_highest (&stop_sched_class)
 #define for_each_class(class) \
    for (class = sched_class_highest; class; class = class->next)
diff --git a/kernel/sched/stop_task.c b/kernel/sched/stop_task.c
index a4147c9d2017..d6ce65dde541 100644
--- a/kernel/sched/stop_task.c
+++ b/kernel/sched/stop_task.c
@@ -31,8 +31,7 @@ pick_next_task_stop(struct rq *rq, struct task_struct *prev)
         if (!stop || !stop->on_rq)
                 return NULL;
 
-        if (prev)
-                prev->sched_class->put_prev_task(rq, prev);
+        put_prev_task(rq, prev);
 
         stop->se.exec_start = rq_clock_task(rq);