sched/core: Simplify helpers for rq clock update skip requests

By renaming the functions we can get rid of the skip parameter
and have better code redability. It makes zero sense to have
things such as:

rq_clock_skip_update(rq, false)

When the skip request is in fact not going to happen. Ever. Rename
things such that we end up with:

rq_clock_skip_update(rq)
rq_clock_cancel_skipupdate(rq)

Signed-off-by: Davidlohr Bueso <[e-mail]>
Acked-by: Peter Zijlstra (Intel) <[e-mail]>
Cc: Linus Torvalds <[e-mail]>
Cc: Mike Galbraith <[e-mail]>
Cc: Thomas Gleixner <[e-mail]>
Cc: [e-mail]
Cc: [e-mail]
Cc: [e-mail]
Link: http://lkml.kernel.org/r/20180404161539.nhadkff2aats74jh@linux-n805
Signed-off-by: Ingo Molnar <[e-mail]>

kernel/sched/core.c

···
 	 * this case, we can save a useless back to back clock update.
 	 */
 	if (task_on_rq_queued(rq->curr) && test_tsk_need_resched(rq->curr))
-		rq_clock_skip_update(rq, true);
+		rq_clock_skip_update(rq);
 }
 
 #ifdef CONFIG_SMP

kernel/sched/deadline.c

···
 	 * so we don't do microscopic update in schedule()
 	 * and double the fastpath cost.
 	 */
-	rq_clock_skip_update(rq, true);
+	rq_clock_skip_update(rq);
 }
 
 #ifdef CONFIG_SMP

kernel/sched/fair.c

···
 		 * so we don't do microscopic update in schedule()
 		 * and double the fastpath cost.
 		 */
-		rq_clock_skip_update(rq, true);
+		rq_clock_skip_update(rq);
 	}
 
 	set_skip_buddy(se);

kernel/sched/rt.c

···
 				 * 'runtime'.
 				 */
 				if (rt_rq->rt_nr_running && rq->curr == rq->idle)
-					rq_clock_skip_update(rq, false);
+					rq_clock_cancel_skipupdate(rq);
 			}
 			if (rt_rq->rt_time || rt_rq->rt_nr_running)
 				idle = 0;

kernel/sched/sched.h

···
 	return rq->clock_task;
 }
 
-static inline void rq_clock_skip_update(struct rq *rq, bool skip)
+static inline void rq_clock_skip_update(struct rq *rq)
 {
 	lockdep_assert_held(&rq->lock);
-	if (skip)
-		rq->clock_update_flags |= RQCF_REQ_SKIP;
-	else
-		rq->clock_update_flags &= ~RQCF_REQ_SKIP;
+	rq->clock_update_flags |= RQCF_REQ_SKIP;
+}
+
+/*
+ * See rt task throttoling, which is the only time a skip
+ * request is cancelled.
+ */
+static inline void rq_clock_cancel_skipupdate(struct rq *rq)
+{
+	lockdep_assert_held(&rq->lock);
+	rq->clock_update_flags &= ~RQCF_REQ_SKIP;
 }
 
 struct rq_flags {