linux-kernel - Re: [PATCH 06/40] sched: add wakeup/sleep sched

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Message-ID: <4B55050B.5020600@kernel.org>
Date:	Tue, 19 Jan 2010 10:04:11 +0900
From:	Tejun Heo <tj@...nel.org>
To:	Peter Zijlstra <peterz@...radead.org>
CC:	torvalds@...ux-foundation.org, mingo@...e.hu, awalls@...ix.net,
	linux-kernel@...r.kernel.org, jeff@...zik.org,
	akpm@...ux-foundation.org, jens.axboe@...cle.com,
	rusty@...tcorp.com.au, cl@...ux-foundation.org,
	dhowells@...hat.com, arjan@...ux.intel.com, avi@...hat.com,
	johannes@...solutions.net, andi@...stfloor.org,
	Mike Galbraith <efault@....de>
Subject: Re: [PATCH 06/40] sched: add wakeup/sleep sched_notifiers and allow
 NULL notifier ops

On 01/18/2010 09:49 PM, Peter Zijlstra wrote:
> On Mon, 2010-01-18 at 20:31 +0900, Tejun Heo wrote:
>> On 01/18/2010 06:57 PM, Peter Zijlstra wrote:
>>> On Mon, 2010-01-18 at 09:57 +0900, Tejun Heo wrote:
>>>
>>>> @@ -2439,6 +2440,8 @@ static inline void ttwu_post_activation(struct task_struct *p, struct rq *rq,
>>>>  		rq->idle_stamp = 0;
>>>>  	}
>>>>  #endif
>>>> +	if (success)
>>>> +		fire_sched_notifiers(p, wakeup);
>>>>  }
>>>>  
>>>>  /**
>>>
>>> So why can't you call fire_sched_notifier(p, wakeup) right next to
>>> activate_task(rq, p, 1) in ttwu_activate() ?
>>
>> I was worried about calling notifier callback before notifying the
>> sched_class of the wakeup.  Conceptually, the notifier callback should
>> be called after all sched internal stuff about the wakeup finish,
>> so...
> 
> I'm thinking that we can place it next to activate_task(), if it makes
> you feel better you can place them both at the end up ttwu_activate()
> instead of in the middle.
> 
> Esp. with the callback you have it really doesn't matter.

Alright, if it's safe, there's no reason to keep it separate with an
extra branch.  I'll move it.

Thanks.

-- 
tejun
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