sched: handle vruntime 64-bit overflow

Handle vruntime overflow by centering the key space around min_vruntime.

( otherwise we could overflow 64-bit vruntime in a few days with SCHED_IDLE
 tasks - or in a few years with nice +19. )

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Mike Galbraith <efault@gmx.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>

diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index 86e5e8c..895fef7 100644 (file)
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -124,11 +124,18 @@ set_leftmost(struct cfs_rq *cfs_rq, struct rb_node *leftmost)
        cfs_rq->rb_leftmost = leftmost;
        if (leftmost) {
                se = rb_entry(leftmost, struct sched_entity, run_node);
-               cfs_rq->min_vruntime = max(se->vruntime,
-                                               cfs_rq->min_vruntime);
+               if ((se->vruntime > cfs_rq->min_vruntime) ||
+                   (cfs_rq->min_vruntime > (1ULL << 61) &&
+                    se->vruntime < (1ULL << 50)))
+                       cfs_rq->min_vruntime = se->vruntime;
        }
 }
 
+s64 entity_key(struct cfs_rq *cfs_rq, struct sched_entity *se)
+{
+       return se->fair_key - cfs_rq->min_vruntime;
+}
+
 /*
  * Enqueue an entity into the rb-tree:
  */
@@ -138,7 +145,7 @@ __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
        struct rb_node **link = &cfs_rq->tasks_timeline.rb_node;
        struct rb_node *parent = NULL;
        struct sched_entity *entry;
-       s64 key = se->fair_key;
+       s64 key = entity_key(cfs_rq, se);
        int leftmost = 1;
 
        /*
@@ -151,7 +158,7 @@ __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
                 * We dont care about collisions. Nodes with
                 * the same key stay together.
                 */
-               if (key - entry->fair_key < 0) {
+               if (key < entity_key(cfs_rq, entry)) {
                        link = &parent->rb_left;
                } else {
                        link = &parent->rb_right;