Hi, Wanpeng,
the commit commentary confuses, I'm agree. Really it's just a cleanup.
On Пт, 2014-10-24 at 07:27 +0800, Wanpeng Li wrote:
> Hi Kirill,
> 8/6/14, 4:06 PM, Kirill Tkhai:
> > (sched_entity::on_rq == 1) does not guarantee the task is pickable;
> > changes on throttled cfs_rq must not lead to reschedule.
>
> Why (sched_entity::on_rq == 1) doesn't guarantee the task is pickable
> since entity will be dequeued during throttling cfs_rq?
Because one of task's (grand)parents in hierarhy may be throtthed and
dequeued.
But task_struct::on_rq check doesn't guarantee this too. So, just ignore
commit commentary; the commentary is wrong.
> > Check for task_struct::on_rq instead.
>
> Do you mean task_struct::on_rq will be cleared during throttling cfs_rq?
> I can't find codes do this.
No, it not cleared. The commit commentary should be:
"sched: Cleanup. Check task_struct::on_rq instead of sched_entity::on_rq,
because it is the same for a task"
> Regards,
> Wanpeng Li
>
> >
> > Signed-off-by: Kirill Tkhai <ktk...@parallels.com>
> > ---
> > kernel/sched/fair.c | 6 +++---
> > 1 file changed, 3 insertions(+), 3 deletions(-)
> >
> > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> > index bfa3c86..6f0ce2b 100644
> > --- a/kernel/sched/fair.c
> > +++ b/kernel/sched/fair.c
> > @@ -7465,7 +7465,7 @@ static void task_fork_fair(struct task_struct *p)
> > static void
> > prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
> > {
> > - if (!p->se.on_rq)
> > + if (!p->on_rq)
> > return;
> >
> > /*
> > @@ -7521,15 +7521,15 @@ static void switched_from_fair(struct rq *rq,
> > struct task_struct *p)
> > */
> > static void switched_to_fair(struct rq *rq, struct task_struct *p)
> > {
> > - struct sched_entity *se = &p->se;
> > #ifdef CONFIG_FAIR_GROUP_SCHED
> > + struct sched_entity *se = &p->se;
> > /*
> > * Since the real-depth could have been changed (only FAIR
> > * class maintain depth value), reset depth properly.
> > */
> > se->depth = se->parent ? se->parent->depth + 1 : 0;
> > #endif
> > - if (!se->on_rq)
> > + if (!p->on_rq)
> > return;
> >
> > /*
> >
> >
> >
> > --
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