linux-kernel - Re: [PATCH 4/7] sched/deadline: reschedule if stop task slip in after pull operations

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Date:	Tue, 21 Apr 2015 07:02:34 +0800
From:	Wanpeng Li <wanpeng.li@...ux.intel.com>
To:	Juri Lelli <juri.lelli@....com>
Cc:	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	linux-kernel@...r.kernel.org,
	Wanpeng Li <wanpeng.li@...ux.intel.com>
Subject: Re: [PATCH 4/7] sched/deadline: reschedule if stop task slip in
 after pull operations

On Tue, Apr 21, 2015 at 06:59:02AM +0800, Wanpeng Li wrote:
>Hi Juri,
>On Mon, Apr 20, 2015 at 11:27:22AM +0100, Juri Lelli wrote:
>>Hi,
>>
>>On 06/04/2015 09:53, Wanpeng Li wrote:
>>> pull_dl_task can drop (and re-acquire) rq->lock, this means a stop task 
>>> can slip in, in which case we need to reschedule. This patch add the 
>>> reschedule when the scenario occurs.
>>> 
>>
>>Ok, I guess it can happen. Doesn't RT have the same problem? It seems that
>>it also has to deal with DL tasks slipping in, right?
>
>Yeah, I will send another patch to handle RT class in the v2 patchset. :)

Oh, I just find I have already done them in patch 7/7.

Regards,
Wanpeng Li 

>
>Regards,
>Wanpeng Li 
>
>>
>>Thanks,
>>
>>- Juri
>>
>>> Signed-off-by: Wanpeng Li <wanpeng.li@...ux.intel.com>
>>> ---
>>>  kernel/sched/deadline.c | 16 +++++++++++++++-
>>>  1 file changed, 15 insertions(+), 1 deletion(-)
>>> 
>>> diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
>>> index b8b9355..844da0f 100644
>>> --- a/kernel/sched/deadline.c
>>> +++ b/kernel/sched/deadline.c
>>> @@ -1739,7 +1739,13 @@ static void switched_from_dl(struct rq *rq, struct task_struct *p)
>>>  	if (!task_on_rq_queued(p) || rq->dl.dl_nr_running)
>>>  		return;
>>>  
>>> -	if (pull_dl_task(rq))
>>> +	/*
>>> +	 * pull_dl_task() can drop (and re-acquire) rq->lock; this
>>> +	 * means a stop task can slip in, in which case we need to
>>> +	 * reschedule.
>>> +	 */
>>> +	if (pull_dl_task(rq) ||
>>> +		(rq->stop && task_on_rq_queued(rq->stop)))
>>>  		resched_curr(rq);
>>>  }
>>>  
>>> @@ -1786,6 +1792,14 @@ static void prio_changed_dl(struct rq *rq, struct task_struct *p,
>>>  			pull_dl_task(rq);
>>>  
>>>  		/*
>>> +		 * pull_dl_task() can drop (and re-acquire) rq->lock; this
>>> +		 * means a stop task can slip in, in which case we need to
>>> +		 * reschedule.
>>> +		 */
>>> +		if (rq->stop && task_on_rq_queued(rq->stop))
>>> +			resched_curr(rq);
>>> +
>>> +		/*
>>>  		 * If we now have a earlier deadline task than p,
>>>  		 * then reschedule, provided p is still on this
>>>  		 * runqueue.
>>> 
--
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