linux-kernel - Re: [RFC][PATCH 2/4] sched: Push put_prev_task() into pick_next

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Message-ID: <4FE2E81C.2040402@linux.vnet.ibm.com>
Date:	Thu, 21 Jun 2012 17:23:40 +0800
From:	Michael Wang <wangyun@...ux.vnet.ibm.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
CC:	mingo@...nel.org, pjt@...gle.com, venki@...gle.com, efault@....de,
	rostedt@...dmis.org, glommer@...allels.com,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC][PATCH 2/4] sched: Push put_prev_task() into pick_next_task()

On 06/21/2012 04:41 PM, Peter Zijlstra wrote:

> On Thu, 2012-06-21 at 15:35 +0800, Michael Wang wrote:
>>> +pick_next_task_fair(struct rq *rq, struct task_struct *prev)
>>>  {
>>>  	struct task_struct *p;
>>>  	struct cfs_rq *cfs_rq = &rq->cfs;
>>> @@ -2999,6 +3000,9 @@ static struct task_struct *pick_next_tas
>>>  	if (!cfs_rq->nr_running)
>>>  		return NULL;
>>>
>>> +	if (prev)
>>> +		prev->sched_class->put_prev_task(rq, prev);
>>> +
>>>  	do {
>>>  		se = pick_next_entity(cfs_rq);
>>>  		set_next_entity(cfs_rq, se);
>>> --- a/kernel/sched/idle_task.c
>>> +++ b/kernel/sched/idle_task.c
>>> @@ -22,8 +22,12 @@ static void check_preempt_curr_idle(stru
>>>  	resched_task(rq->idle);
>>>  }
>>
>> Will it cause trouble when the last task on cfs_rq was dequeued before
>> been putted?
>>
>> The cfs_rq->nr_running will be 0 and we will miss the chance to put
>> prev, will we?
> 
> pick_next_task_idle() will then do the put, no?

Oh, that's right, I see.

> 


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