[tip: sched/core] sched: Use fair:prio_changed() instead of ad-hoc implementation

[tip-bot2 for Frederic Weisbecker]

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

Commit-ID:     5443a0be6121d557e12951537e10159e4c61035d
Gitweb:        https://git.kernel.org/tip/5443a0be6121d557e12951537e10159e4c61035d
Author:        Frederic Weisbecker <frederic@xxxxxxxxxx>
AuthorDate:    Tue, 03 Dec 2019 17:01:06 +01:00
Committer:     Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Tue, 17 Dec 2019 13:32:50 +01:00

sched: Use fair:prio_changed() instead of ad-hoc implementation

set_user_nice() implements its own version of fair::prio_changed() and
therefore misses a specific optimization towards nohz_full CPUs that
avoid sending an resched IPI to a reniced task running alone. Use the
proper callback instead.

Reported-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Signed-off-by: Frederic Weisbecker <frederic@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Link: https://lkml.kernel.org/r/20191203160106.18806-3-frederic@xxxxxxxxxx
---
 kernel/sched/core.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 90e4b00..15508c2 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -4540,17 +4540,17 @@ void set_user_nice(struct task_struct *p, long nice)
 	p->prio = effective_prio(p);
 	delta = p->prio - old_prio;
 
-	if (queued) {
+	if (queued)
 		enqueue_task(rq, p, ENQUEUE_RESTORE | ENQUEUE_NOCLOCK);
-		/*
-		 * If the task increased its priority or is running and
-		 * lowered its priority, then reschedule its CPU:
-		 */
-		if (delta < 0 || (delta > 0 && task_running(rq, p)))
-			resched_curr(rq);
-	}
 	if (running)
 		set_next_task(rq, p);
+
+	/*
+	 * If the task increased its priority or is running and
+	 * lowered its priority, then reschedule its CPU:
+	 */
+	p->sched_class->prio_changed(rq, p, old_prio);
+
 out_unlock:
 	task_rq_unlock(rq, p, &rf);
 }