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?
>
> 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.
Regards,
Wanpeng Li
>
> Signed-off-by: Kirill Tkhai <[email protected]>
> ---
> 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;
>
> /*
>
>
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to [email protected]
> More majordomo info at http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at http://www.tux.org/lkml/
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 <[email protected]>
> > ---
> > 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;
> >
> > /*
> >
> >
> >
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> > the body of a message to [email protected]
> > More majordomo info at http://vger.kernel.org/majordomo-info.html
> > Please read the FAQ at http://www.tux.org/lkml/
>
Hi Kirill,
10/24/14, 2:01 PM, Kirill Tkhai:
> 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"
IIUR, for fair class, sched_entity::on_rq will be set/clear during
enqueue/dequeue, task_struct::on_rq will changed during task migration,
I'm not sure why they are the same.
Regards,
Wanpeng Li
>
>
>> Regards,
>> Wanpeng Li
>>
>>> Signed-off-by: Kirill Tkhai <[email protected]>
>>> ---
>>> 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;
>>>
>>> /*
>>>
>>>
>>>
>>> --
>>> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
>>> the body of a message to [email protected]
>>> More majordomo info at http://vger.kernel.org/majordomo-info.html
>>> Please read the FAQ at http://www.tux.org/lkml/
>
В Пт, 24/10/2014 в 17:32 +0800, Wanpeng Li пишет:
> Hi Kirill,
> 10/24/14, 2:01 PM, Kirill Tkhai:
> > 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"
>
> IIUR, for fair class, sched_entity::on_rq will be set/clear during
> enqueue/dequeue, task_struct::on_rq will changed during task migration,
> I'm not sure why they are the same.
prio_changed_fair() and switched_to_fair() can't be called during migration.
They are called under pi_lock, and migration needs this lock too.
> >>> Signed-off-by: Kirill Tkhai <[email protected]>
> >>> ---
> >>> 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;
> >>>
> >>> /*
> >>>
> >>>
> >>>
> >>> --
> >>> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> >>> the body of a message to [email protected]
> >>> More majordomo info at http://vger.kernel.org/majordomo-info.html
> >>> Please read the FAQ at http://www.tux.org/lkml/
> >
>