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SubjectRe: [PATCH 1/3] sched/deadline: clear dl_entity params when setscheduling to different class
Hi,

On 21/10/14 13:15, Wanpeng Li wrote:
> ping,
>
> 于 10/8/14, 8:32 PM, Wanpeng Li 写道:
>> Hi Juri,
>>
>> 于 9/19/14, 5:22 PM, Juri Lelli 写道:
>>> When a task is using SCHED_DEADLINE and the user setschedules it to a
>>> different
>>> class its sched_dl_entity static parameters are not cleaned up. This
>>> causes a
>>> bug if the user sets it back to SCHED_DEADLINE with the same
>>> parameters again.
>>> The problem resides in the check we perform at the very beginning of
>>> dl_overflow():
>>>
>>> if (new_bw == p->dl.dl_bw)
>>> return 0;
>>>
>>> This condition is met in the case depicted above, so the function
>>> returns and
>>> dl_b->total_bw is not updated (the p->dl.dl_bw is not added to it).
>>> After this,
>>
>> As you know there is no static parameter clear before this patch, so
>> if p->dl.dl_bw will decrease from dl_b->total_bw when the user
>> setschedules to a different class instead of dl?
>>

We remove p->dl.dl_bw from dl_b->total_bw in dl_overflow(). Then this
patch introduces the clearing of p->dl params.

Thanks,

- Juri

>> Regards,
>> Wanpeng Li
>>
>>> admission control is broken.
>>>
>>> This patch fixes the thing, properly clearing static parameters for a
>>> task
>>> that ceases to use SCHED_DEADLINE.
>>>
>>> Reported-by: Daniele Alessandrelli <daniele.alessandrelli@gmail.com>
>>> Reported-by: Daniel Wagner <daniel.wagner@bmw-carit.de>
>>> Reported-by: Vincent Legout <vincent@legout.info>
>>> Tested-by: Luca Abeni <luca.abeni@unitn.it>
>>> Signed-off-by: Juri Lelli <juri.lelli@arm.com>
>>> Cc: Ingo Molnar <mingo@redhat.com>
>>> Cc: Peter Zijlstra <peterz@infradead.org>
>>> Cc: Juri Lelli <juri.lelli@gmail.com>
>>> Cc: Dario Faggioli <raistlin@linux.it>
>>> Cc: Michael Trimarchi <michael@amarulasolutions.com>
>>> Cc: Fabio Checconi <fchecconi@gmail.com>
>>> Cc: linux-kernel@vger.kernel.org
>>> ---
>>> kernel/sched/core.c | 19 +++++++++++++++----
>>> kernel/sched/deadline.c | 2 ++
>>> kernel/sched/sched.h | 3 +++
>>> 3 files changed, 20 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
>>> index ec1a286..581a429 100644
>>> --- a/kernel/sched/core.c
>>> +++ b/kernel/sched/core.c
>>> @@ -1776,6 +1776,20 @@ int wake_up_state(struct task_struct *p,
>>> unsigned int state)
>>> }
>>> /*
>>> + * This function clears the sched_dl_entity static params.
>>> + */
>>> +void __dl_clear_params(struct task_struct *p)
>>> +{
>>> + struct sched_dl_entity *dl_se = &p->dl;
>>> +
>>> + dl_se->dl_runtime = 0;
>>> + dl_se->dl_deadline = 0;
>>> + dl_se->dl_period = 0;
>>> + dl_se->flags = 0;
>>> + dl_se->dl_bw = 0;
>>> +}
>>> +
>>> +/*
>>> * Perform scheduler related setup for a newly forked process p.
>>> * p is forked by current.
>>> *
>>> @@ -1799,10 +1813,7 @@ static void __sched_fork(unsigned long
>>> clone_flags, struct task_struct *p)
>>> RB_CLEAR_NODE(&p->dl.rb_node);
>>> hrtimer_init(&p->dl.dl_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
>>> - p->dl.dl_runtime = p->dl.runtime = 0;
>>> - p->dl.dl_deadline = p->dl.deadline = 0;
>>> - p->dl.dl_period = 0;
>>> - p->dl.flags = 0;
>>> + __dl_clear_params(p);
>>> INIT_LIST_HEAD(&p->rt.run_list);
>>> diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
>>> index 255ce13..4a51b14 100644
>>> --- a/kernel/sched/deadline.c
>>> +++ b/kernel/sched/deadline.c
>>> @@ -1569,6 +1569,8 @@ static void switched_from_dl(struct rq *rq,
>>> struct task_struct *p)
>>> if (hrtimer_active(&p->dl.dl_timer) && !dl_policy(p->policy))
>>> hrtimer_try_to_cancel(&p->dl.dl_timer);
>>> + __dl_clear_params(p);
>>> +
>>> #ifdef CONFIG_SMP
>>> /*
>>> * Since this might be the only -deadline task on the rq,
>>> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
>>> index 579712f..4890484 100644
>>> --- a/kernel/sched/sched.h
>>> +++ b/kernel/sched/sched.h
>>> @@ -126,6 +126,9 @@ struct rt_bandwidth {
>>> u64 rt_runtime;
>>> struct hrtimer rt_period_timer;
>>> };
>>> +
>>> +void __dl_clear_params(struct task_struct *p);
>>> +
>>> /*
>>> * To keep the bandwidth of -deadline tasks and groups under control
>>> * we need some place where:
>>
>
>

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