linux-kernel - Re: [PATCH -tip] sched: Pair ttwu_activate() with uwtt

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Date:	Wed, 16 Jan 2013 16:05:58 +0100
From:	Mike Galbraith <bitbucket@...ine.de>
To:	Alexander Gordeev <agordeev@...hat.com>
Cc:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH -tip] sched: Pair ttwu_activate() with uwtt_deactivate()

On Wed, 2013-01-16 at 11:14 +0100, Alexander Gordeev wrote: 
> Try to make reading of __schedule() bit more easy.

You didn't succeed in doing that for me.  Moving that code away just
obfuscates the special case for worker-bees scheduling off, and while
ttwu is shorthand for try_to_wake_up, uuwt is.. a lysdexic typo.

> Signed-off-by: Alexander Gordeev <agordeev@...hat.com>
> ---
>  kernel/sched/core.c |   42 ++++++++++++++++++++++++------------------
>  1 files changed, 24 insertions(+), 18 deletions(-)
> 
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 38413f6..dd54ded 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -1272,6 +1272,27 @@ static void ttwu_activate(struct rq *rq, struct task_struct *p, int en_flags)
>  		wq_worker_waking_up(p, cpu_of(rq));
>  }
>  
> +static void try_to_wake_up_local(struct task_struct *p);
> +
> +static void uwtt_deactivate(struct rq *rq, struct task_struct *p, int de_flags)
> +{
> +	deactivate_task(rq, p, de_flags);
> +	p->on_rq = 0;
> +
> +	/*
> +	 * If a worker went to sleep, notify and ask workqueue
> +	 * whether it wants to wake up a task to maintain
> +	 * concurrency.
> +	 */
> +	if (p->flags & PF_WQ_WORKER) {
> +		struct task_struct *to_wakeup;
> +
> +		to_wakeup = wq_worker_sleeping(p, cpu_of(rq));
> +		if (to_wakeup)
> +			try_to_wake_up_local(to_wakeup);
> +	}
> +}
> +
>  /*
>   * Mark the task runnable and perform wakeup-preemption.
>   */
> @@ -2907,25 +2928,10 @@ need_resched:
>  
>  	switch_count = &prev->nivcsw;
>  	if (prev->state && !(preempt_count() & PREEMPT_ACTIVE)) {
> -		if (unlikely(signal_pending_state(prev->state, prev))) {
> +		if (unlikely(signal_pending_state(prev->state, prev)))
>  			prev->state = TASK_RUNNING;
> -		} else {
> -			deactivate_task(rq, prev, DEQUEUE_SLEEP);
> -			prev->on_rq = 0;
> -
> -			/*
> -			 * If a worker went to sleep, notify and ask workqueue
> -			 * whether it wants to wake up a task to maintain
> -			 * concurrency.
> -			 */
> -			if (prev->flags & PF_WQ_WORKER) {
> -				struct task_struct *to_wakeup;
> -
> -				to_wakeup = wq_worker_sleeping(prev, cpu);
> -				if (to_wakeup)
> -					try_to_wake_up_local(to_wakeup);
> -			}
> -		}
> +		else
> +			uwtt_deactivate(rq, prev, DEQUEUE_SLEEP);
>  		switch_count = &prev->nvcsw;
>  	}
>  
> -- 
> 1.7.7.6
> 
> 


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