[RFC][PATCH 04/16] sched/{rt,deadline}: Fix set_next_task vs pick_next_task

Peter Zijlstra
2019-02-18T17:40:35Z

Because pick_next_task() implies set_curr_task() and some of the
details haven't matter too much, some of what _should_ be in
set_curr_task() ended up in pick_next_task, correct this.

This prepares the way for a pick_next_task() variant that does not
affect the current state; allowing remote picking.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
kernel/sched/deadline.c | 23 ++++++++++++-----------
kernel/sched/rt.c | 27 ++++++++++++++-------------
2 files changed, 26 insertions(+), 24 deletions(-)

--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -1695,12 +1695,21 @@ static void start_hrtick_dl(struct rq *r
}
#endif

-static inline void set_next_task(struct rq *rq, struct task_struct *p)
+static void set_next_task_dl(struct rq *rq, struct task_struct *p)
{
p->se.exec_start = rq_clock_task(rq);

/* You can't push away the running task */
dequeue_pushable_dl_task(rq, p);
+
+ if (hrtick_enabled(rq))
+ start_hrtick_dl(rq, p);
+
+ if (rq->curr->sched_class != &dl_sched_class)
+ update_dl_rq_load_avg(rq_clock_pelt(rq), rq, 0);
+
+ if (rq->curr != p)
+ deadline_queue_push_tasks(rq);
}

static struct sched_dl_entity *pick_next_dl_entity(struct rq *rq,
@@ -1759,15 +1768,7 @@ pick_next_task_dl(struct rq *rq, struct

p = dl_task_of(dl_se);

- set_next_task(rq, p);
-
- if (hrtick_enabled(rq))
- start_hrtick_dl(rq, p);
-
- deadline_queue_push_tasks(rq);
-
- if (rq->curr->sched_class != &dl_sched_class)
- update_dl_rq_load_avg(rq_clock_pelt(rq), rq, 0);
+ set_next_task_dl(rq, p);

return p;
}
@@ -1814,7 +1815,7 @@ static void task_fork_dl(struct task_str

static void set_curr_task_dl(struct rq *rq)
{
- set_next_task(rq, rq->curr);
+ set_next_task_dl(rq, rq->curr);
}

#ifdef CONFIG_SMP
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -1498,12 +1498,23 @@ static void check_preempt_curr_rt(struct
#endif
}

-static inline void set_next_task(struct rq *rq, struct task_struct *p)
+static inline void set_next_task_rt(struct rq *rq, struct task_struct *p)
{
p->se.exec_start = rq_clock_task(rq);

/* The running task is never eligible for pushing */
dequeue_pushable_task(rq, p);
+
+ /*
+ * If prev task was rt, put_prev_task() has already updated the
+ * utilization. We only care of the case where we start to schedule a
+ * rt task
+ */
+ if (rq->curr->sched_class != &rt_sched_class)
+ update_rt_rq_load_avg(rq_clock_pelt(rq), rq, 0);
+
+ if (rq->curr != p)
+ rt_queue_push_tasks(rq);
}

static struct sched_rt_entity *pick_next_rt_entity(struct rq *rq,
@@ -1577,17 +1588,7 @@ pick_next_task_rt(struct rq *rq, struct

p = _pick_next_task_rt(rq);

- set_next_task(rq, p);
-
- rt_queue_push_tasks(rq);
-
- /*
- * If prev task was rt, put_prev_task() has already updated the
- * utilization. We only care of the case where we start to schedule a
- * rt task
- */
- if (rq->curr->sched_class != &rt_sched_class)
- update_rt_rq_load_avg(rq_clock_pelt(rq), rq, 0);
+ set_next_task_rt(rq, p);

return p;
}
@@ -2356,7 +2357,7 @@ static void task_tick_rt(struct rq *rq,

static void set_curr_task_rt(struct rq *rq)
{
- set_next_task(rq, rq->curr);
+ set_next_task_rt(rq, rq->curr);
}

static unsigned int get_rr_interval_rt(struct rq *rq, struct task_struct *task)