[RFC PATCH v5 07/29] sched/rt: Remove unnecessary runqueue pointer in struct rt_rq

[Yuri Andriaccio <yurand2000@gmail.com>]

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 served_rq_of_rt_rq to retrieve the runqueue the given rt_rq is
serving.

Signed-off-by: Yuri Andriaccio <yurand2000@gmail.com>
---
 kernel/sched/rt.c    |  7 ++-----
 kernel/sched/sched.h | 21 +++++++++++++--------
 2 files changed, 15 insertions(+), 13 deletions(-)

diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 392212ac90d8..dd4aee5570aa 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 = served_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 = served_rq_of_rt_rq(rt_rq);

 	queue_balance_callback(rq, &per_cpu(rt_pull_head, rq->cpu), pull_rt_task);
 }
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 5833905d8eaa..770de5afd3a9 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -850,8 +850,6 @@ 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 */
@@ -3308,11 +3306,16 @@ static inline struct task_struct *rt_task_of(struct sched_rt_entity *rt_se)
 	return container_of_const(rt_se, struct task_struct, rt);
 }

+static inline struct rq *served_rq_of_rt_rq(struct rt_rq *rt_rq)
+{
+	WARN_ON(!rt_group_sched_enabled() && rt_rq->tg != &root_task_group);
+	return container_of_const(rt_rq, struct rq, rt);
+}
+
 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 cpu_rq(served_rq_of_rt_rq(rt_rq)->cpu);
 }

 static inline struct rt_rq *rt_rq_of_se(struct sched_rt_entity *rt_se)
@@ -3323,10 +3326,7 @@ static inline struct rt_rq *rt_rq_of_se(struct sched_rt_entity *rt_se)

 static inline struct rq *rq_of_rt_se(struct sched_rt_entity *rt_se)
 {
-	struct rt_rq *rt_rq = rt_se->rt_rq;
-
-	WARN_ON(!rt_group_sched_enabled() && rt_rq->tg != &root_task_group);
-	return rt_rq->rq;
+	return rq_of_rt_rq(rt_se->rt_rq);
 }
 #else
 static inline struct task_struct *rt_task_of(struct sched_rt_entity *rt_se)
@@ -3334,6 +3334,11 @@ static inline struct task_struct *rt_task_of(struct sched_rt_entity *rt_se)
 	return container_of_const(rt_se, struct task_struct, rt);
 }

+static inline struct rq *served_rq_of_rt_rq(struct rt_rq *rt_rq)
+{
+	return container_of_const(rt_rq, struct rq, rt);
+}
+
 static inline struct rq *rq_of_rt_rq(struct rt_rq *rt_rq)
 {
 	return container_of_const(rt_rq, struct rq, rt);
--
2.53.0