[tip: sched/core] sched: Extract the task putting code from pick_next_task()

[tip-bot2 for Chen Yu]

The following commit has been merged into the sched/core branch of tip:

Commit-ID:     457d1f465778ccb5f14f7d7a62245e41d12a3804
Gitweb:        https://git.kernel.org/tip/457d1f465778ccb5f14f7d7a62245e41d12a3804
Author:        Chen Yu <yu.c.chen@xxxxxxxxx>
AuthorDate:    Tue, 21 Apr 2020 18:50:43 +08:00
Committer:     Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Thu, 30 Apr 2020 20:14:40 +02:00

sched: Extract the task putting code from pick_next_task()

Introduce a new function put_prev_task_balance() to do the balance
when necessary, and then put previous task back to the run queue.
This function is extracted from pick_next_task() to prepare for
future usage by other type of task picking logic.

No functional change.

Suggested-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Signed-off-by: Chen Yu <yu.c.chen@xxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Reviewed-by: Valentin Schneider <valentin.schneider@xxxxxxx>
Reviewed-by: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
Reviewed-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
Link: https://lkml.kernel.org/r/5a99860cf66293db58a397d6248bcb2eee326776.1587464698.git.yu.c.chen@xxxxxxxxx
---
 kernel/sched/core.c | 39 +++++++++++++++++++++++----------------
 1 file changed, 23 insertions(+), 16 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 9a2fbf9..2e6ba9e 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3899,6 +3899,28 @@ static inline void schedule_debug(struct task_struct *prev, bool preempt)
 	schedstat_inc(this_rq()->sched_count);
 }
 
+static void put_prev_task_balance(struct rq *rq, struct task_struct *prev,
+				  struct rq_flags *rf)
+{
+#ifdef CONFIG_SMP
+	const struct sched_class *class;
+	/*
+	 * We must do the balancing pass before put_prev_task(), such
+	 * that when we release the rq->lock the task is in the same
+	 * state as before we took rq->lock.
+	 *
+	 * We can terminate the balance pass as soon as we know there is
+	 * a runnable task of @class priority or higher.
+	 */
+	for_class_range(class, prev->sched_class, &idle_sched_class) {
+		if (class->balance(rq, prev, rf))
+			break;
+	}
+#endif
+
+	put_prev_task(rq, prev);
+}
+
 /*
  * Pick up the highest-prio task:
  */
@@ -3932,22 +3954,7 @@ pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
 	}
 
 restart:
-#ifdef CONFIG_SMP
-	/*
-	 * We must do the balancing pass before put_next_task(), such
-	 * that when we release the rq->lock the task is in the same
-	 * state as before we took rq->lock.
-	 *
-	 * We can terminate the balance pass as soon as we know there is
-	 * a runnable task of @class priority or higher.
-	 */
-	for_class_range(class, prev->sched_class, &idle_sched_class) {
-		if (class->balance(rq, prev, rf))
-			break;
-	}
-#endif
-
-	put_prev_task(rq, prev);
+	put_prev_task_balance(rq, prev, rf);
 
 	for_each_class(class) {
 		p = class->pick_next_task(rq);