[RFC PATCH v6 08/25] sched/rt: Remove unnecessary runqueue pointer in struct rt_rq

[Yuri Andriaccio]

Remove the rq field in struct rt_rq.
  The rq field now is just caching the pointer to the global runqueue of the
  given rt_rq, so it is unnecessary as the global runqueue can be retrieved
  in other ways.

Introduce global_rq_of_rt_rq to retrieve the global runqueue which serves a
rt_rq's dl_server.
Rework rq_of_rt_rq to retrieve the runqueue a rt_rq is serving.

Signed-off-by: Yuri Andriaccio <yurand2000@xxxxxxxxx>
---
 kernel/sched/rt.c    | 21 +++++++++------------
 kernel/sched/sched.h | 16 ++++++++++++----
 2 files changed, 21 insertions(+), 16 deletions(-)

diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 7b526a86083c..4575c234ae46 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -101,10 +101,7 @@ void init_tg_rt_entry(struct task_group *tg, struct rt_rq *rt_rq,
 		struct sched_rt_entity *rt_se, int cpu,
 		struct sched_rt_entity *parent)
 {
-	struct rq *rq = cpu_rq(cpu);
-
 	rt_rq->highest_prio.curr = MAX_RT_PRIO-1;
-	rt_rq->rq = rq;
 	rt_rq->tg = tg;

 	tg->rt_rq[cpu] = rt_rq;
@@ -184,7 +181,7 @@ static void pull_rt_task(struct rq *);

 static inline void rt_queue_push_tasks(struct rt_rq *rt_rq)
 {
-	struct rq *rq = container_of_const(rt_rq, struct rq, rt);
+	struct rq *rq = global_rq_of_rt_rq(rt_rq);

 	if (!has_pushable_tasks(rt_rq))
 		return;
@@ -194,7 +191,7 @@ static inline void rt_queue_push_tasks(struct rt_rq *rt_rq)

 static inline void rt_queue_pull_task(struct rt_rq *rt_rq)
 {
-	struct rq *rq = container_of_const(rt_rq, struct rq, rt);
+	struct rq *rq = global_rq_of_rt_rq(rt_rq);

 	queue_balance_callback(rq, &per_cpu(rt_pull_head, rq->cpu), pull_rt_task);
 }
@@ -222,7 +219,7 @@ static void enqueue_pushable_task(struct rt_rq *rt_rq, struct task_struct *p)
 		rt_rq->highest_prio.next = p->prio;

 	if (!rt_rq->overloaded) {
-		rt_set_overload(rq_of_rt_rq(rt_rq));
+		rt_set_overload(global_rq_of_rt_rq(rt_rq));
 		rt_rq->overloaded = 1;
 	}
 }
@@ -240,7 +237,7 @@ static void dequeue_pushable_task(struct rt_rq *rt_rq, struct task_struct *p)
 		rt_rq->highest_prio.next = MAX_RT_PRIO-1;

 		if (rt_rq->overloaded) {
-			rt_clear_overload(rq_of_rt_rq(rt_rq));
+			rt_clear_overload(global_rq_of_rt_rq(rt_rq));
 			rt_rq->overloaded = 0;
 		}
 	}
@@ -495,7 +492,7 @@ update_stats_wait_start_rt(struct rt_rq *rt_rq, struct sched_rt_entity *rt_se)
 	if (!stats)
 		return;

-	__update_stats_wait_start(rq_of_rt_rq(rt_rq), p, stats);
+	__update_stats_wait_start(global_rq_of_rt_rq(rt_rq), p, stats);
 }

 static inline void
@@ -512,7 +509,7 @@ update_stats_enqueue_sleeper_rt(struct rt_rq *rt_rq, struct sched_rt_entity *rt_
 	if (!stats)
 		return;

-	__update_stats_enqueue_sleeper(rq_of_rt_rq(rt_rq), p, stats);
+	__update_stats_enqueue_sleeper(global_rq_of_rt_rq(rt_rq), p, stats);
 }

 static inline void
@@ -540,7 +537,7 @@ update_stats_wait_end_rt(struct rt_rq *rt_rq, struct sched_rt_entity *rt_se)
 	if (!stats)
 		return;

-	__update_stats_wait_end(rq_of_rt_rq(rt_rq), p, stats);
+	__update_stats_wait_end(global_rq_of_rt_rq(rt_rq), p, stats);
 }

 static inline void
@@ -564,11 +561,11 @@ update_stats_dequeue_rt(struct rt_rq *rt_rq, struct sched_rt_entity *rt_se,
 		state = READ_ONCE(p->__state);
 		if (state & TASK_INTERRUPTIBLE)
 			__schedstat_set(p->stats.sleep_start,
-					rq_clock(rq_of_rt_rq(rt_rq)));
+					rq_clock(global_rq_of_rt_rq(rt_rq)));

 		if (state & TASK_UNINTERRUPTIBLE)
 			__schedstat_set(p->stats.block_start,
-					rq_clock(rq_of_rt_rq(rt_rq)));
+					rq_clock(global_rq_of_rt_rq(rt_rq)));
 	}
 }

diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index a217c4ab6660..3aa29fe932fc 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -857,8 +857,6 @@ struct rt_rq {
 	raw_spinlock_t		rt_runtime_lock;

 	unsigned int		rt_nr_boosted;
-
-	struct rq		*rq; /* this is always top-level rq, cache? */
 #endif
 #ifdef CONFIG_CGROUP_SCHED
 	struct task_group	*tg; /* this tg has "this" rt_rq on given CPU for runnable entities */
@@ -3337,9 +3335,14 @@ static inline struct task_struct *rt_task_of(struct sched_rt_entity *rt_se)

 static inline struct rq *rq_of_rt_rq(struct rt_rq *rt_rq)
 {
-	/* Cannot fold with non-CONFIG_RT_GROUP_SCHED version, layout */
 	WARN_ON(!rt_group_sched_enabled() && rt_rq->tg != &root_task_group);
-	return rt_rq->rq;
+	return container_of_const(rt_rq, struct rq, rt);
+}
+
+static inline struct rq *global_rq_of_rt_rq(struct rt_rq *rt_rq)
+{
+	/* Cannot fold with non-CONFIG_RT_GROUP_SCHED version, layout */
+	return cpu_rq(rq_of_rt_rq(rt_rq)->cpu);
 }

 static inline struct rt_rq *rt_rq_of_se(struct sched_rt_entity *rt_se)
@@ -3358,6 +3361,11 @@ static inline struct rq *rq_of_rt_rq(struct rt_rq *rt_rq)
 	return container_of_const(rt_rq, struct rq, rt);
 }

+static inline struct rq *global_rq_of_rt_rq(struct rt_rq *rt_rq)
+{
+	return container_of_const(rt_rq, struct rq, rt);
+}
+
 static inline struct rt_rq *rt_rq_of_se(struct sched_rt_entity *rt_se)
 {
 	struct rq *rq = task_rq(rt_task_of(rt_se));
--
2.54.0