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@infradead.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20191203160106.18806-3-frederic@kernel.org

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 90e4b00..15508c2 100644 (file)
--- 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);
 }