sched/core: Make pick_next_task_idle() more consistent

Only pick_next_task_fair() needs the @prev and @rf argument; these are
required to implement the cpu-cgroup optimization. None of the other
pick_next_task() methods need this. Make pick_next_task_idle() more
consistent.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: bsegall@google.com
Cc: dietmar.eggemann@arm.com
Cc: juri.lelli@redhat.com
Cc: ktkhai@virtuozzo.com
Cc: mgorman@suse.de
Cc: qais.yousef@arm.com
Cc: qperret@google.com
Cc: rostedt@goodmis.org
Cc: valentin.schneider@arm.com
Cc: vincent.guittot@linaro.org
Link: https://lkml.kernel.org/r/20191108131909.545730862@infradead.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 0f2eb3629070700fdc0911e0c0dd495a91ebf386..59c4f29634175695566002766e1ccce083bf83f4 100644 (file)
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3922,8 +3922,10 @@ pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
                        goto restart;
 
                /* Assumes fair_sched_class->next == idle_sched_class */
-               if (unlikely(!p))
-                       p = idle_sched_class.pick_next_task(rq, prev, rf);
+               if (unlikely(!p)) {
+                       put_prev_task(rq, prev);
+                       p = idle_sched_class.pick_next_task(rq, NULL, NULL);
+               }
 
                return p;
        }

diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c
index f65ef1e2f20413c604edef762dd05ada0ef60fa7..179d1d4ac5a66f39fef876ea0aabeeefc747361c 100644 (file)
--- a/kernel/sched/idle.c
+++ b/kernel/sched/idle.c
@@ -396,8 +396,7 @@ pick_next_task_idle(struct rq *rq, struct task_struct *prev, struct rq_flags *rf
 {
        struct task_struct *next = rq->idle;
 
-       if (prev)
-               put_prev_task(rq, prev);
+       WARN_ON_ONCE(prev || rf);
 
        set_next_task_idle(rq, next);