[tip:sched/urgent] sched: Account for vruntime wrapping

tip-bot for Fabio Checconi
2009-07-18T09:50:26Z

Commit-ID: 54fdc5816631b43ba55fc3206d7add2d85850bc6
Gitweb: http://git.kernel.org/tip/54fdc5816631b43ba55fc3206d7add2d85850bc6
Author: Fabio Checconi <fabio@gandalf.sssup.it>
AuthorDate: Thu, 16 Jul 2009 12:32:27 +0200
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Sat, 18 Jul 2009 11:17:08 +0200

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>

---
kernel/sched_fair.c | 10 ++++++++--
1 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index 7c248dc..9ffb2b2 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.