From: Byungchul Park <byungchul.p...@lge.com>
current code ensures a task has a normalized vruntime when switching off
from fair class, but it does not ensure the task has a non-normalized
vruntime when switching back to the fair class.
this is an example breaking this consistency.
1. a task is in fair class and !queue
2. change its class to rt class (still !queue)
3. change its class to fair class again (stll !queue)
Signed-off-by: Byungchul Park <byungchul.p...@lge.com>
---
kernel/sched/fair.c | 16 +++++++++++++++-
1 file changed, 15 insertions(+), 1 deletion(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index ffa70dc..df265f5 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -8150,8 +8150,22 @@ static void switched_to_fair(struct rq *rq, struct
task_struct *p)
*/
se->depth = se->parent ? se->parent->depth + 1 : 0;
#endif
- if (!task_on_rq_queued(p))
+
+ if (!task_on_rq_queued(p)) {
+
+ /*
+ * Ensure the task has a non-normalized vruntime when it is
switched
+ * back to the fair class with !queued, so that
enqueue_entity() at
+ * wake-up time will do the right thing.
+ *
+ * If it's queued, then the enqueue_entity(.flags=0) makes the
task
+ * has non-normalized vruntime, if it's !queued, then it still
has
+ * normalized vruntime.
+ */
+ if (p->state != TASK_RUNNING)
+ se->vruntime += cfs_rq_of(se)->min_vruntime;
return;
+ }
/*
* We were most likely switched from sched_rt, so
--
1.7.9.5
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