1 files changed, 21 insertions, 5 deletions

diff --git a/kernel/sched.c b/kernel/sched.c
index b4dab63c6dbd..0ec84f57695d 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -1941,6 +1941,7 @@ int can_migrate_task(task_t *p, runqueue_t *rq, int this_cpu,
         return 1;
 }
 
+#define rq_best_prio(rq) min((rq)->curr->prio, (rq)->best_expired_prio)
 /*
  * move_tasks tries to move up to max_nr_move tasks and max_load_move weighted
  * load from busiest to this_rq, as part of a balancing operation within
@@ -1955,7 +1956,9 @@ static int move_tasks(runqueue_t *this_rq, int this_cpu, runqueue_t *busiest,
 {
         prio_array_t *array, *dst_array;
         struct list_head *head, *curr;
-        int idx, pulled = 0, pinned = 0, this_min_prio;
+        int idx, pulled = 0, pinned = 0, this_best_prio, busiest_best_prio;
+        int busiest_best_prio_seen;
+        int skip_for_load; /* skip the task based on weighted load issues */
         long rem_load_move;
         task_t *tmp;
 
@@ -1964,7 +1967,16 @@ static int move_tasks(runqueue_t *this_rq, int this_cpu, runqueue_t *busiest,
 
         rem_load_move = max_load_move;
         pinned = 1;
-        this_min_prio = this_rq->curr->prio;
+        this_best_prio = rq_best_prio(this_rq);
+        busiest_best_prio = rq_best_prio(busiest);
+        /*
+         * Enable handling of the case where there is more than one task
+         * with the best priority.   If the current running task is one
+         * of those with prio==busiest_best_prio we know it won't be moved
+         * and therefore it's safe to override the skip (based on load) of
+         * any task we find with that prio.
+         */
+        busiest_best_prio_seen = busiest_best_prio == busiest->curr->prio;
 
         /*
          * We first consider expired tasks. Those will likely not be
@@ -2009,8 +2021,12 @@ skip_queue:
          * skip a task if it will be the highest priority task (i.e. smallest
          * prio value) on its new queue regardless of its load weight
          */
-        if ((idx >= this_min_prio && tmp->load_weight > rem_load_move) ||
+        skip_for_load = tmp->load_weight > rem_load_move;
+        if (skip_for_load && idx < this_best_prio)
+                skip_for_load = !busiest_best_prio_seen && idx == busiest_best_prio;
+        if (skip_for_load ||
             !can_migrate_task(tmp, busiest, this_cpu, sd, idle, &pinned)) {
+                busiest_best_prio_seen |= idx == busiest_best_prio;
                 if (curr != head)
                         goto skip_queue;
                 idx++;
@@ -2031,8 +2047,8 @@ skip_queue:
          * and the prescribed amount of weighted load.
          */
         if (pulled < max_nr_move && rem_load_move > 0) {
-                if (idx < this_min_prio)
-                        this_min_prio = idx;
+                if (idx < this_best_prio)
+                        this_best_prio = idx;
                 if (curr != head)
                         goto skip_queue;
                 idx++;