[PATCH v5 2/2] sched/core: Reorganize ttwu_do_wakeup() and ttwu_do_activate()

[Chengming Zhou]

ttwu_do_activate() is used for a complete wakeup, in which we will
activate_task() and use ttwu_do_wakeup() to mark the task runnable
and perform wakeup-preemption, also call class->task_woken() callback
and update the rq->idle_stamp.

Since ttwu_runnable() is not a complete wakeup, don't need all those
done in ttwu_do_wakeup(), so we can move those to ttwu_do_activate()
to simplify ttwu_do_wakeup(), making it only mark the task runnable
to be reused in ttwu_runnable() and try_to_wake_up().

This patch should not have any functional changes.

Suggested-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Signed-off-by: Chengming Zhou <zhouchengming@xxxxxxxxxxxxx>
---
 kernel/sched/core.c | 64 ++++++++++++++++++++++-----------------------
 1 file changed, 31 insertions(+), 33 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 60aa7774e5f4..d8216485b0ad 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3623,14 +3623,39 @@ ttwu_stat(struct task_struct *p, int cpu, int wake_flags)
 }
 
 /*
- * Mark the task runnable and perform wakeup-preemption.
+ * Mark the task runnable.
  */
-static void ttwu_do_wakeup(struct rq *rq, struct task_struct *p, int wake_flags,
-			   struct rq_flags *rf)
+static inline void ttwu_do_wakeup(struct task_struct *p)
 {
-	check_preempt_curr(rq, p, wake_flags);
 	WRITE_ONCE(p->__state, TASK_RUNNING);
 	trace_sched_wakeup(p);
+}
+
+static void
+ttwu_do_activate(struct rq *rq, struct task_struct *p, int wake_flags,
+		 struct rq_flags *rf)
+{
+	int en_flags = ENQUEUE_WAKEUP | ENQUEUE_NOCLOCK;
+
+	lockdep_assert_rq_held(rq);
+
+	if (p->sched_contributes_to_load)
+		rq->nr_uninterruptible--;
+
+#ifdef CONFIG_SMP
+	if (wake_flags & WF_MIGRATED)
+		en_flags |= ENQUEUE_MIGRATED;
+	else
+#endif
+	if (p->in_iowait) {
+		delayacct_blkio_end(p);
+		atomic_dec(&task_rq(p)->nr_iowait);
+	}
+
+	activate_task(rq, p, en_flags);
+	check_preempt_curr(rq, p, wake_flags);
+
+	ttwu_do_wakeup(p);
 
 #ifdef CONFIG_SMP
 	if (p->sched_class->task_woken) {
@@ -3660,31 +3685,6 @@ static void ttwu_do_wakeup(struct rq *rq, struct task_struct *p, int wake_flags,
 #endif
 }
 
-static void
-ttwu_do_activate(struct rq *rq, struct task_struct *p, int wake_flags,
-		 struct rq_flags *rf)
-{
-	int en_flags = ENQUEUE_WAKEUP | ENQUEUE_NOCLOCK;
-
-	lockdep_assert_rq_held(rq);
-
-	if (p->sched_contributes_to_load)
-		rq->nr_uninterruptible--;
-
-#ifdef CONFIG_SMP
-	if (wake_flags & WF_MIGRATED)
-		en_flags |= ENQUEUE_MIGRATED;
-	else
-#endif
-	if (p->in_iowait) {
-		delayacct_blkio_end(p);
-		atomic_dec(&task_rq(p)->nr_iowait);
-	}
-
-	activate_task(rq, p, en_flags);
-	ttwu_do_wakeup(rq, p, wake_flags, rf);
-}
-
 /*
  * Consider @p being inside a wait loop:
  *
@@ -3726,8 +3726,7 @@ static int ttwu_runnable(struct task_struct *p, int wake_flags)
 			update_rq_clock(rq);
 			check_preempt_curr(rq, p, wake_flags);
 		}
-		WRITE_ONCE(p->__state, TASK_RUNNING);
-		trace_sched_wakeup(p);
+		ttwu_do_wakeup(p);
 		ret = 1;
 	}
 	__task_rq_unlock(rq, &rf);
@@ -4093,8 +4092,7 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
 			goto out;
 
 		trace_sched_waking(p);
-		WRITE_ONCE(p->__state, TASK_RUNNING);
-		trace_sched_wakeup(p);
+		ttwu_do_wakeup(p);
 		goto out;
 	}
 
-- 
2.37.2