sched/fair: replace cfs_rq->rb_leftmost

... with the generic rbtree flavor instead. No changes
in semantics whatsoever.

Link: http://lkml.kernel.org/r/20170719014603.19029-8-dave@stgolabs.net
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kernel/sched/debug.c

@@ -530,7 +530,7 @@ void print_cfs_rq(struct seq_file *m, int cpu, struct cfs_rq *cfs_rq)
 			SPLIT_NS(cfs_rq->exec_clock));
 
 	raw_spin_lock_irqsave(&rq->lock, flags);
-	if (cfs_rq->rb_leftmost)
+	if (rb_first_cached(&cfs_rq->tasks_timeline))
 		MIN_vruntime = (__pick_first_entity(cfs_rq))->vruntime;
 	last = __pick_last_entity(cfs_rq);
 	if (last)

kernel/sched/fair.c

@@ -513,6 +513,7 @@ static inline int entity_before(struct sched_entity *a,
 static void update_min_vruntime(struct cfs_rq *cfs_rq)
 {
 	struct sched_entity *curr = cfs_rq->curr;
+	struct rb_node *leftmost = rb_first_cached(&cfs_rq->tasks_timeline);
 
 	u64 vruntime = cfs_rq->min_vruntime;
 
@@ -523,10 +524,9 @@ static void update_min_vruntime(struct cfs_rq *cfs_rq)
 			curr = NULL;
 	}
 
-	if (cfs_rq->rb_leftmost) {
-		struct sched_entity *se = rb_entry(cfs_rq->rb_leftmost,
-						   struct sched_entity,
-						   run_node);
+	if (leftmost) { /* non-empty tree */
+		struct sched_entity *se;
+		se = rb_entry(leftmost, struct sched_entity, run_node);
 
 		if (!curr)
 			vruntime = se->vruntime;
@@ -547,10 +547,10 @@ static void update_min_vruntime(struct cfs_rq *cfs_rq)
  */
 static void __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
 {
-	struct rb_node **link = &cfs_rq->tasks_timeline.rb_node;
+	struct rb_node **link = &cfs_rq->tasks_timeline.rb_root.rb_node;
 	struct rb_node *parent = NULL;
 	struct sched_entity *entry;
-	int leftmost = 1;
+	bool leftmost = true;
 
 	/*
 	 * Find the right place in the rbtree:
@@ -566,36 +566,23 @@ static void __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
 			link = &parent->rb_left;
 		} else {
 			link = &parent->rb_right;
-			leftmost = 0;
+			leftmost = false;
 		}
 	}
 
-	/*
-	 * Maintain a cache of leftmost tree entries (it is frequently
-	 * used):
-	 */
-	if (leftmost)
-		cfs_rq->rb_leftmost = &se->run_node;
-
 	rb_link_node(&se->run_node, parent, link);
-	rb_insert_color(&se->run_node, &cfs_rq->tasks_timeline);
+	rb_insert_color_cached(&se->run_node,
+			       &cfs_rq->tasks_timeline, leftmost);
 }
 
 static void __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
 {
-	if (cfs_rq->rb_leftmost == &se->run_node) {
-		struct rb_node *next_node;
-
-		next_node = rb_next(&se->run_node);
-		cfs_rq->rb_leftmost = next_node;
-	}
-
-	rb_erase(&se->run_node, &cfs_rq->tasks_timeline);
+	rb_erase_cached(&se->run_node, &cfs_rq->tasks_timeline);
 }
 
 struct sched_entity *__pick_first_entity(struct cfs_rq *cfs_rq)
 {
-	struct rb_node *left = cfs_rq->rb_leftmost;
+	struct rb_node *left = rb_first_cached(&cfs_rq->tasks_timeline);
 
 	if (!left)
 		return NULL;
@@ -616,7 +603,7 @@ static struct sched_entity *__pick_next_entity(struct sched_entity *se)
 #ifdef CONFIG_SCHED_DEBUG
 struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq)
 {
-	struct rb_node *last = rb_last(&cfs_rq->tasks_timeline);
+	struct rb_node *last = rb_last(&cfs_rq->tasks_timeline.rb_root);
 
 	if (!last)
 		return NULL;
@@ -9312,7 +9299,7 @@ static void set_curr_task_fair(struct rq *rq)
 
 void init_cfs_rq(struct cfs_rq *cfs_rq)
 {
-	cfs_rq->tasks_timeline = RB_ROOT;
+	cfs_rq->tasks_timeline = RB_ROOT_CACHED;
 	cfs_rq->min_vruntime = (u64)(-(1LL << 20));
 #ifndef CONFIG_64BIT
 	cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;

kernel/sched/sched.h

@@ -426,8 +426,7 @@ struct cfs_rq {
 	u64 min_vruntime_copy;
 #endif
 
-	struct rb_root tasks_timeline;
-	struct rb_node *rb_leftmost;
+	struct rb_root_cached tasks_timeline;
 
 	/*
 	 * 'curr' points to currently running entity on this cfs_rq.