sched: yield fix

fix yield bugs due to the current-not-in-rbtree changes: the task is
not in the rbtree so rbtree-removal is a no-no.

[ From: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>: build fix. ]

also, nice code size reduction:

kernel/sched.o:
   text    data     bss     dec     hex filename
  38323    3506      24   41853    a37d sched.o.before
  38236    3506      24   41766    a326 sched.o.after

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Dmitry Adamushko <dmitry.adamushko@gmail.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 5 insertions, 20 deletions

diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index 5384a977c9a7..fcd6900849b3 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -739,9 +739,7 @@ static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int sleep)
 static void yield_task_fair(struct rq *rq)
 {
         struct cfs_rq *cfs_rq = task_cfs_rq(rq->curr);
-        struct rb_node **link = &cfs_rq->tasks_timeline.rb_node;
         struct sched_entity *rightmost, *se = &rq->curr->se;
-        struct rb_node *parent;
 
         /*
          * Are we the only task in the tree?
@@ -755,39 +753,26 @@ static void yield_task_fair(struct rq *rq)
                  * Dequeue and enqueue the task to update its
                  * position within the tree:
                  */
-                dequeue_entity(cfs_rq, se, 0);
-                enqueue_entity(cfs_rq, se, 0);
+                update_curr(cfs_rq);
 
                 return;
         }
         /*
          * Find the rightmost entry in the rbtree:
          */
-        do {
-                parent = *link;
-                link = &parent->rb_right;
-        } while (*link);
-
-        rightmost = rb_entry(parent, struct sched_entity, run_node);
+        rightmost = __pick_last_entity(cfs_rq);
         /*
          * Already in the rightmost position?
          */
-        if (unlikely(rightmost == se))
+        if (unlikely(rightmost->vruntime < se->vruntime))
                 return;
 
         /*
          * Minimally necessary key value to be last in the tree:
+         * Upon rescheduling, sched_class::put_prev_task() will place
+         * 'current' within the tree based on its new key value.
          */
         se->vruntime = rightmost->vruntime + 1;
-
-        if (cfs_rq->rb_leftmost == &se->run_node)
-                cfs_rq->rb_leftmost = rb_next(&se->run_node);
-        /*
-         * Relink the task to the rightmost position:
-         */
-        rb_erase(&se->run_node, &cfs_rq->tasks_timeline);
-        rb_link_node(&se->run_node, parent, link);
-        rb_insert_color(&se->run_node, &cfs_rq->tasks_timeline);
 }
 
 /*