sched/fair: Move unused stub functions to header

These four functions have a normal definition for CONFIG_FAIR_GROUP_SCHED,
and empty one that is only referenced when FAIR_GROUP_SCHED is disabled
but CGROUP_SCHED is still enabled. If both are turned off, the functions
are still defined but the misisng prototype causes a W=1 warning:

kernel/sched/fair.c:12544:6: error: no previous prototype for 'free_fair_sched_group'
kernel/sched/fair.c:12546:5: error: no previous prototype for 'alloc_fair_sched_group'
kernel/sched/fair.c:12553:6: error: no previous prototype for 'online_fair_sched_group'
kernel/sched/fair.c:12555:6: error: no previous prototype for 'unregister_fair_sched_group'

Move the alternatives into the header as static inline functions with
the correct combination of #ifdef checks to avoid the warning without
adding even more complexity.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lore.kernel.org/r/20230522195021.3456768-6-arnd@kernel.org

kernel/sched/fair.c

@@ -684,7 +684,7 @@ struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq)
 /**************************************************************
  * Scheduling class statistics methods:
  */
-#ifdef CONFIG_SMP
+
 int sched_update_scaling(void)
 {
 	unsigned int factor = get_update_sysctl_factor();
@@ -702,7 +702,6 @@ int sched_update_scaling(void)
 	return 0;
 }
 #endif
-#endif
 
 /*
  * delta /= w
@@ -6169,8 +6168,9 @@ static inline int throttled_lb_pair(struct task_group *tg,
 	return 0;
 }
 
-#ifdef CONFIG_FAIR_GROUP_SCHED
 void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
+
+#ifdef CONFIG_FAIR_GROUP_SCHED
 static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
 #endif
 

kernel/sched/sched.h

@@ -1245,7 +1245,6 @@ static inline raw_spinlock_t *__rq_lockp(struct rq *rq)
 
 bool cfs_prio_less(const struct task_struct *a, const struct task_struct *b,
 			bool fi);
-void task_vruntime_update(struct rq *rq, struct task_struct *p, bool in_fi);
 
 /*
  * Helpers to check if the CPU's core cookie matches with the task's cookie
@@ -2377,7 +2376,6 @@ static inline struct cpuidle_state *idle_get_state(struct rq *rq)
 #endif
 
 extern void schedule_idle(void);
-asmlinkage void schedule_user(void);
 
 extern void sysrq_sched_debug_show(void);
 extern void sched_init_granularity(void);