[RFC PATCH v6 04/25] sched/deadline: Distinguish between dl_rq and my_q

[Yuri Andriaccio <yurand2000@gmail.com>]

From: luca abeni <luca.abeni@santannapisa.it>

Split the single runqueue pointer in sched_dl_entity into two separate
pointers, following the existing pattern used by sched_rt_entity:

- dl_rq: Points to the deadline runqueue where this entity is queued
         (global runqueue).
- my_q:  Points to the runqueue that this entity serves (for servers).

This distinction is currently redundant for the fair_server and ext_servers
(both point to the same CPU's structures), but is essential for future RT
cgroup support where deadline servers will be queued on the global dl_rq while
serving tasks from cgroup-specific runqueues.

Update rq_of_dl_se() to use container_of_const() to recover the global rq from
dl_rq, and update fair.c and ext.c to explicitly use my_q (local rq) when
accessing the served runqueue.

Update dl_server_init() to take a dl_rq pointer (use to retrieve the
global runqueue where the dl_server is scheduled) and a rq pointer (for
the local runqueue served by the server).

Signed-off-by: luca abeni <luca.abeni@santannapisa.it>
Signed-off-by: Yuri Andriaccio <yurand2000@gmail.com>
---
 include/linux/sched.h   |  6 ++++--
 kernel/sched/deadline.c | 17 ++++++++++++-----
 kernel/sched/ext.c      |  4 ++--
 kernel/sched/fair.c     |  4 ++--
 kernel/sched/sched.h    |  3 ++-
 5 files changed, 22 insertions(+), 12 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index ee06cba5c6f5..411ffe9b34b3 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -733,9 +733,11 @@ struct sched_dl_entity {
 	 * Bits for DL-server functionality. Also see the comment near
 	 * dl_server_update().
 	 *
-	 * @rq the runqueue this server is for
+	 * @dl_rq the runqueue on which this entity is (to be) queued
+	 * @my_q  the runqueue "owned" by this entity
 	 */
-	struct rq			*rq;
+	struct dl_rq                    *dl_rq;
+	struct rq                       *my_q;
 	dl_server_pick_f		server_pick_task;

 #ifdef CONFIG_RT_MUTEXES
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 63e88ecdd5ed..b3059658a74a 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -65,10 +65,12 @@ static inline struct rq *rq_of_dl_rq(struct dl_rq *dl_rq)

 static inline struct rq *rq_of_dl_se(struct sched_dl_entity *dl_se)
 {
-	struct rq *rq = dl_se->rq;
+	struct rq *rq;

 	if (!dl_server(dl_se))
 		rq = task_rq(dl_task_of(dl_se));
+	else
+		rq = container_of_const(dl_se->dl_rq, struct rq, dl);

 	return rq;
 }
@@ -1817,11 +1819,14 @@ void dl_server_start(struct sched_dl_entity *dl_se)

 void dl_server_stop(struct sched_dl_entity *dl_se)
 {
+	struct rq *rq;
+
 	if (!dl_server(dl_se) || !dl_server_active(dl_se))
 		return;

-	trace_sched_dl_server_stop_tp(dl_se, cpu_of(dl_se->rq),
-				      dl_get_type(dl_se, dl_se->rq));
+	rq = rq_of_dl_se(dl_se);
+	trace_sched_dl_server_stop_tp(dl_se, cpu_of(rq),
+				      dl_get_type(dl_se, rq));
 	dequeue_dl_entity(dl_se, DEQUEUE_SLEEP);
 	hrtimer_try_to_cancel(&dl_se->dl_timer);
 	dl_se->dl_defer_armed = 0;
@@ -1830,10 +1835,12 @@ void dl_server_stop(struct sched_dl_entity *dl_se)
 	dl_se->dl_server_active = 0;
 }

-void dl_server_init(struct sched_dl_entity *dl_se, struct rq *rq,
+void dl_server_init(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq,
+		    struct rq *served_rq,
 		    dl_server_pick_f pick_task)
 {
-	dl_se->rq = rq;
+	dl_se->dl_rq = dl_rq;
+	dl_se->my_q  = served_rq;
 	dl_se->server_pick_task = pick_task;
 }

diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index 65631e577ee9..306bd22a4731 100644
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -3252,7 +3252,7 @@ ext_server_pick_task(struct sched_dl_entity *dl_se, struct rq_flags *rf)
 	if (!scx_enabled())
 		return NULL;

-	return do_pick_task_scx(dl_se->rq, rf, true);
+	return do_pick_task_scx(dl_se->my_q, rf, true);
 }

 /*
@@ -3264,7 +3264,7 @@ void ext_server_init(struct rq *rq)

 	init_dl_entity(dl_se);

-	dl_server_init(dl_se, rq, ext_server_pick_task);
+	dl_server_init(dl_se, &rq->dl, rq, ext_server_pick_task);
 }

 #ifdef CONFIG_SCHED_CORE
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 3ebec186f982..2bc749ae9203 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -9315,7 +9315,7 @@ pick_next_task_fair(struct rq *rq, struct task_struct *prev, struct rq_flags *rf
 static struct task_struct *
 fair_server_pick_task(struct sched_dl_entity *dl_se, struct rq_flags *rf)
 {
-	return pick_task_fair(dl_se->rq, rf);
+	return pick_task_fair(dl_se->my_q, rf);
 }

 void fair_server_init(struct rq *rq)
@@ -9324,7 +9324,7 @@ void fair_server_init(struct rq *rq)

 	init_dl_entity(dl_se);

-	dl_server_init(dl_se, rq, fair_server_pick_task);
+	dl_server_init(dl_se, &rq->dl, rq, fair_server_pick_task);
 }

 /*
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 9f63b15d309d..970386ce4dbf 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -412,7 +412,8 @@ extern void dl_server_update_idle(struct sched_dl_entity *dl_se, s64 delta_exec)
 extern void dl_server_update(struct sched_dl_entity *dl_se, s64 delta_exec);
 extern void dl_server_start(struct sched_dl_entity *dl_se);
 extern void dl_server_stop(struct sched_dl_entity *dl_se);
-extern void dl_server_init(struct sched_dl_entity *dl_se, struct rq *rq,
+extern void dl_server_init(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq,
+		    struct rq *served_rq,
 		    dl_server_pick_f pick_task);
 extern void sched_init_dl_servers(void);

--
2.54.0