[GIT PULL] scheduler fix

[Ingo Molnar]

Linus,

Please pull the latest sched-urgent-for-linus git tree from:

   git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git 
sched-urgent-for-linus

   # HEAD: 53d3bc773eaa7ab1cf63585e76af7ee869d5e709 Revert "sched/fair: Fix 
fairness issue on migration"

This is a revert to fix an interactivity problem. The proper fixes for the 
problems that the reverted commit exposed are now in sched/core (consisting of 
3 
patches), but were too risky for v4.6 and will arrive in the v4.7 merge window.

 Thanks,

        Ingo

------------------>
Ingo Molnar (1):
      Revert "sched/fair: Fix fairness issue on migration"


 kernel/sched/fair.c | 20 ++++++--------------
 1 file changed, 6 insertions(+), 14 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 40748dc8ea3e..e7dd0ec169be 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -3188,25 +3188,17 @@ static inline void check_schedstat_required(void)
 static void
 enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
 {
-       bool renorm = !(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_WAKING);
-       bool curr = cfs_rq->curr == se;
-
        /*
-        * If we're the current task, we must renormalise before calling
-        * update_curr().
+        * Update the normalized vruntime before updating min_vruntime
+        * through calling update_curr().
         */
-       if (renorm && curr)
+       if (!(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_WAKING))
                se->vruntime += cfs_rq->min_vruntime;
 
-       update_curr(cfs_rq);
-
        /*
-        * Otherwise, renormalise after, such that we're placed at the current
-        * moment in time, instead of some random moment in the past.
+        * Update run-time statistics of the 'current'.
         */
-       if (renorm && !curr)
-               se->vruntime += cfs_rq->min_vruntime;
-
+       update_curr(cfs_rq);
        enqueue_entity_load_avg(cfs_rq, se);
        account_entity_enqueue(cfs_rq, se);
        update_cfs_shares(cfs_rq);
@@ -3222,7 +3214,7 @@ enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity 
*se, int flags)
                update_stats_enqueue(cfs_rq, se);
                check_spread(cfs_rq, se);
        }
-       if (!curr)
+       if (se != cfs_rq->curr)
                __enqueue_entity(cfs_rq, se);
        se->on_rq = 1;