2023-08-01 07:25:09

by Yajun Deng

Subject: [PATCH] sched/rt: move back to RT_GROUP_SCHED and rename it child

The member back in struct sched_rt_entity only related to RT_GROUP_SCHED,
it should not place out of RT_GROUP_SCHED, move back to RT_GROUP_SCHED
and rename it child.

Init child in init_tg_rt_entry(). Also, remove the case parent is NULL
because this case is the same as rt_se is NULL and already returned.

Introduce for_each_sched_rt_entity_reverse() to iterate entries from
top to down.

Signed-off-by: Yajun Deng <[email protected]>
---
include/linux/sched.h | 2 +-
kernel/sched/rt.c | 28 +++++++++++++++-------------
2 files changed, 16 insertions(+), 14 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 177b3f3676ef..5635655d6c35 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -594,8 +594,8 @@ struct sched_rt_entity {
unsigned short on_rq;
unsigned short on_list;

- struct sched_rt_entity *back;
#ifdef CONFIG_RT_GROUP_SCHED
+ struct sched_rt_entity *child;
struct sched_rt_entity *parent;
/* rq on which this entity is (to be) queued: */
struct rt_rq *rt_rq;
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 00e0e5074115..75efb1027b9f 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -228,13 +228,10 @@ void init_tg_rt_entry(struct task_group *tg, struct rt_rq *rt_rq,
if (!rt_se)
return;

- if (!parent)
- rt_se->rt_rq = &rq->rt;
- else
- rt_se->rt_rq = parent->my_q;
-
+ rt_se->rt_rq = parent->my_q;
rt_se->my_q = rt_rq;
rt_se->parent = parent;
+ parent->child = rt_se;
INIT_LIST_HEAD(&rt_se->run_list);
}

@@ -564,6 +561,9 @@ static inline struct task_group *next_task_group(struct task_group *tg)
#define for_each_sched_rt_entity(rt_se) \
for (; rt_se; rt_se = rt_se->parent)

+#define for_each_sched_rt_entity_reverse(rt_se) \
+ for (; rt_se; rt_se = rt_se->child)
+
static inline struct rt_rq *group_rt_rq(struct sched_rt_entity *rt_se)
{
return rt_se->my_q;
@@ -669,6 +669,9 @@ typedef struct rt_rq *rt_rq_iter_t;
#define for_each_sched_rt_entity(rt_se) \
for (; rt_se; rt_se = NULL)

+#define for_each_sched_rt_entity_reverse(rt_se) \
+ for_each_sched_rt_entity(rt_se)
+
static inline struct rt_rq *group_rt_rq(struct sched_rt_entity *rt_se)
{
return NULL;
@@ -1481,22 +1484,21 @@ static void __dequeue_rt_entity(struct sched_rt_entity *rt_se, unsigned int flag
*/
static void dequeue_rt_stack(struct sched_rt_entity *rt_se, unsigned int flags)
{
- struct sched_rt_entity *back = NULL;
+ struct sched_rt_entity *parent = NULL;
unsigned int rt_nr_running;

- for_each_sched_rt_entity(rt_se) {
- rt_se->back = back;
- back = rt_se;
- }
+ for_each_sched_rt_entity(rt_se)
+ parent = rt_se;

- rt_nr_running = rt_rq_of_se(back)->rt_nr_running;
+ rt_nr_running = rt_rq_of_se(parent)->rt_nr_running;

- for (rt_se = back; rt_se; rt_se = rt_se->back) {
+ rt_se = parent;
+ for_each_sched_rt_entity_reverse(rt_se) {
if (on_rt_rq(rt_se))
__dequeue_rt_entity(rt_se, flags);
}

- dequeue_top_rt_rq(rt_rq_of_se(back), rt_nr_running);
+ dequeue_top_rt_rq(rt_rq_of_se(parent), rt_nr_running);
}

static void enqueue_rt_entity(struct sched_rt_entity *rt_se, unsigned int flags)
--
2.25.1

2023-08-01 14:15:25

by Steven Rostedt

Subject: Re: [PATCH] sched/rt: move back to RT_GROUP_SCHED and rename it child

On Tue, 1 Aug 2023 14:27:14 +0800
Yajun Deng <[email protected]> wrote:

> @@ -228,13 +228,10 @@ void init_tg_rt_entry(struct task_group *tg, struct rt_rq *rt_rq,
> if (!rt_se)
> return;
>
> - if (!parent)
> - rt_se->rt_rq = &rq->rt;
> - else
> - rt_se->rt_rq = parent->my_q;
> -
> + rt_se->rt_rq = parent->my_q;

So when this is called with parent = NULL, this will crash?

-- Steve

> rt_se->my_q = rt_rq;
> rt_se->parent = parent;
> + parent->child = rt_se;
> INIT_LIST_HEAD(&rt_se->run_list);
> }
>

2023-08-01 15:05:22

by Steven Rostedt

Subject: Re: [PATCH] sched/rt: move back to RT_GROUP_SCHED and rename it child

On Tue, 1 Aug 2023 10:00:30 -0400
Steven Rostedt <[email protected]> wrote:

> On Tue, 1 Aug 2023 14:27:14 +0800
> Yajun Deng <[email protected]> wrote:
>
> > @@ -228,13 +228,10 @@ void init_tg_rt_entry(struct task_group *tg, struct rt_rq *rt_rq,
> > if (!rt_se)
> > return;

Ah, I missed the second part of your change log where you said parent is
only NULL when rt_se is NULL.

I would then add:

if (!rt_se)
return;

if (WARN_ON_ONCE(!parent))
return;

-- Steve


> >
> > - if (!parent)
> > - rt_se->rt_rq = &rq->rt;
> > - else
> > - rt_se->rt_rq = parent->my_q;
> > -
> > + rt_se->rt_rq = parent->my_q;
>
> So when this is called with parent = NULL, this will crash?
>
> -- Steve
>
> > rt_se->my_q = rt_rq;
> > rt_se->parent = parent;
> > + parent->child = rt_se;
> > INIT_LIST_HEAD(&rt_se->run_list);
> > }
> >