sched: Account for vruntime wrapping

I spotted two sites that didn't take vruntime wrap-around into
account. Fix these by creating a comparison helper that does do
so.

Signed-off-by: Fabio Checconi <fabio@gandalf.sssup.it>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 8 insertions, 2 deletions

diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index 7c248dc30f41..9ffb2b2ceba4 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -266,6 +266,12 @@ static inline u64 min_vruntime(u64 min_vruntime, u64 vruntime)
         return min_vruntime;
 }
 
+static inline int entity_before(struct sched_entity *a,
+                                struct sched_entity *b)
+{
+        return (s64)(a->vruntime - b->vruntime) < 0;
+}
+
 static inline s64 entity_key(struct cfs_rq *cfs_rq, struct sched_entity *se)
 {
         return se->vruntime - cfs_rq->min_vruntime;
@@ -1017,7 +1023,7 @@ static void yield_task_fair(struct rq *rq)
         /*
          * Already in the rightmost position?
          */
-        if (unlikely(!rightmost || rightmost->vruntime < se->vruntime))
+        if (unlikely(!rightmost || entity_before(rightmost, se)))
                 return;
 
         /*
@@ -1713,7 +1719,7 @@ static void task_new_fair(struct rq *rq, struct task_struct *p)
 
         /* 'curr' will be NULL if the child belongs to a different group */
         if (sysctl_sched_child_runs_first && this_cpu == task_cpu(p) &&
-                        curr && curr->vruntime < se->vruntime) {
+                        curr && entity_before(curr, se)) {
                 /*
                  * Upon rescheduling, sched_class::put_prev_task() will place
                  * 'current' within the tree based on its new key value.