sched/fair: Remove unused cfs_rq_clock_task() function

cfs_rq_clock_task() was first introduced and used in:

  f1b17280 ("sched: Maintain runnable averages across throttled periods")

Over time its use has been graduately removed by the following commits:

  d31b1a66 ("sched/fair: Factorize PELT update")
  23127296 ("sched/fair: Update scale invariance of PELT")

Today, there is no single user left, so it can be safely removed.

Found via the -Wunused-function build warning.
Signed-off-by: Qian Cai <cai@lca.pw>
Cc: Ben Segall <bsegall@google.com>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/1568668775-2127-1-git-send-email-cai@lca.pw
[ Rewrote the changelog. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>

kernel/sched/fair.c

@@ -749,7 +749,6 @@ void init_entity_runnable_average(struct sched_entity *se)
 	/* when this task enqueue'ed, it will contribute to its cfs_rq's load_avg */
 }
 
-static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq);
 static void attach_entity_cfs_rq(struct sched_entity *se);
 
 /*
@@ -4376,15 +4375,6 @@ static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
 	return &tg->cfs_bandwidth;
 }
 
-/* rq->task_clock normalized against any time this cfs_rq has spent throttled */
-static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
-{
-	if (unlikely(cfs_rq->throttle_count))
-		return cfs_rq->throttled_clock_task - cfs_rq->throttled_clock_task_time;
-
-	return rq_clock_task(rq_of(cfs_rq)) - cfs_rq->throttled_clock_task_time;
-}
-
 /* returns 0 on failure to allocate runtime */
 static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)
 {
@@ -4476,7 +4466,6 @@ static int tg_unthrottle_up(struct task_group *tg, void *data)
 
 	cfs_rq->throttle_count--;
 	if (!cfs_rq->throttle_count) {
-		/* adjust cfs_rq_clock_task() */
 		cfs_rq->throttled_clock_task_time += rq_clock_task(rq) -
 					     cfs_rq->throttled_clock_task;
 
@@ -5080,11 +5069,6 @@ static inline bool cfs_bandwidth_used(void)
 	return false;
 }
 
-static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
-{
-	return rq_clock_task(rq_of(cfs_rq));
-}
-
 static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) {}
 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq) { return false; }
 static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {}