[tip: sched/core] sched: Remove struct sched_class::next field

[tip-bot2 for Steven Rostedt (VMware)]

The following commit has been merged into the sched/core branch of tip:

Commit-ID:     a87e749e8fa1aaef9b4db32e21c2795e69ce67bf
Gitweb:        https://git.kernel.org/tip/a87e749e8fa1aaef9b4db32e21c2795e69ce67bf
Author:        Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
AuthorDate:    Thu, 19 Dec 2019 16:44:54 -05:00
Committer:     Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Thu, 25 Jun 2020 13:45:44 +02:00

sched: Remove struct sched_class::next field

Now that the sched_class descriptors are defined in order via the linker
script vmlinux.lds.h, there's no reason to have a "next" pointer to the
previous priroity structure. The order of the sturctures can be aligned as
an array, and used to index and find the next sched_class descriptor.

Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Link: https://lkml.kernel.org/r/20191219214558.845353593@xxxxxxxxxxx
---
 kernel/sched/deadline.c  | 1 -
 kernel/sched/fair.c      | 1 -
 kernel/sched/idle.c      | 1 -
 kernel/sched/rt.c        | 1 -
 kernel/sched/sched.h     | 1 -
 kernel/sched/stop_task.c | 1 -
 6 files changed, 6 deletions(-)

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index d9e7946..c9cc1d6 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -2481,7 +2481,6 @@ static void prio_changed_dl(struct rq *rq, struct task_struct *p,
 
 const struct sched_class dl_sched_class
 	__attribute__((section("__dl_sched_class"))) = {
-	.next			= &rt_sched_class,
 	.enqueue_task		= enqueue_task_dl,
 	.dequeue_task		= dequeue_task_dl,
 	.yield_task		= yield_task_dl,
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 3365f6b..a63f400 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -11124,7 +11124,6 @@ static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task
  */
 const struct sched_class fair_sched_class
 	__attribute__((section("__fair_sched_class"))) = {
-	.next			= &idle_sched_class,
 	.enqueue_task		= enqueue_task_fair,
 	.dequeue_task		= dequeue_task_fair,
 	.yield_task		= yield_task_fair,
diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c
index f580629..336d478 100644
--- a/kernel/sched/idle.c
+++ b/kernel/sched/idle.c
@@ -455,7 +455,6 @@ static void update_curr_idle(struct rq *rq)
  */
 const struct sched_class idle_sched_class
 	__attribute__((section("__idle_sched_class"))) = {
-	/* .next is NULL */
 	/* no enqueue/yield_task for idle tasks */
 
 	/* dequeue is not valid, we print a debug message there: */
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 6543d44..f215eea 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -2431,7 +2431,6 @@ static unsigned int get_rr_interval_rt(struct rq *rq, struct task_struct *task)
 
 const struct sched_class rt_sched_class
 	__attribute__((section("__rt_sched_class"))) = {
-	.next			= &fair_sched_class,
 	.enqueue_task		= enqueue_task_rt,
 	.dequeue_task		= dequeue_task_rt,
 	.yield_task		= yield_task_rt,
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 4165c06..549e7e6 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1754,7 +1754,6 @@ extern const u32		sched_prio_to_wmult[40];
 #define RETRY_TASK		((void *)-1UL)
 
 struct sched_class {
-	const struct sched_class *next;
 
 #ifdef CONFIG_UCLAMP_TASK
 	int uclamp_enabled;
diff --git a/kernel/sched/stop_task.c b/kernel/sched/stop_task.c
index f4bbd54..394bc81 100644
--- a/kernel/sched/stop_task.c
+++ b/kernel/sched/stop_task.c
@@ -111,7 +111,6 @@ static void update_curr_stop(struct rq *rq)
  */
 const struct sched_class stop_sched_class
 	__attribute__((section("__stop_sched_class"))) = {
-	.next			= &dl_sched_class,
 
 	.enqueue_task		= enqueue_task_stop,
 	.dequeue_task		= dequeue_task_stop,