[core-scheduling] Modify prio_less() with in CONFIG_SCHED_CORE

From: JaeJoon Jung
Date: Tue Oct 18 2022 - 08:42:59 EST


Hello,
Since the priority of sched_class can be determined by pointer operation,
the prio_less() function can be modified as follows.
With this fix, the __task_prio() function is not needed.
Please review.

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index ee28253c9ac0..24b86773da04 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -154,21 +154,6 @@ __read_mostly int scheduler_running;

DEFINE_STATIC_KEY_FALSE(__sched_core_enabled);

-/* kernel prio, less is more */
-static inline int __task_prio(struct task_struct *p)
-{
- if (p->sched_class == &stop_sched_class) /* trumps deadline */
- return -2;
-
- if (rt_prio(p->prio)) /* includes deadline */
- return p->prio; /* [-1, 99] */
-
- if (p->sched_class == &idle_sched_class)
- return MAX_RT_PRIO + NICE_WIDTH; /* 140 */
-
- return MAX_RT_PRIO + MAX_NICE; /* 120, squash fair */
-}
-
/*
* l(a,b)
* le(a,b) := !l(b,a)
@@ -179,22 +164,18 @@ static inline int __task_prio(struct task_struct *p)
/* real prio, less is less */
static inline bool prio_less(struct task_struct *a, struct
task_struct *b, bool in_fi)
{
-
- int pa = __task_prio(a), pb = __task_prio(b);
-
- if (-pa < -pb)
- return true;
-
- if (-pb < -pa)
- return false;
-
- if (pa == -1) /* dl_prio() doesn't work because of stop_class above */
- return !dl_time_before(a->dl.deadline, b->dl.deadline);
-
- if (pa == MAX_RT_PRIO + MAX_NICE) /* fair */
- return cfs_prio_less(a, b, in_fi);
-
- return false;
+ int less = a->sched_class - b->sched_class;
+
+ if (less) {
+ return (less > 0) ? true : false;
+ } else {
+ if (a->sched_class == &fair_sched_class)
+ return cfs_prio_less(a, b, in_fi);
+ else if (a->sched_class == &dl_sched_class)
+ return !dl_time_before(a->dl.deadline, b->dl.deadline);
+ else
+ return (a->prio - b->prio > 0) ? true : false;
+ }
}

Thanks,
JaeJoon Jung.