linux-kernel - Re: [PATCH] sched: Update unlikely to now likely in sched_move

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Date:   Sat, 4 Feb 2017 12:06:45 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     "Steven Rostedt (VMware)" <rostedt@...dmis.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Oleg Nesterov <oleg@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>
Subject: Re: [PATCH] sched: Update unlikely to now likely in sched_move_task()

On Fri, Feb 03, 2017 at 03:30:19PM -0500, Steven Rostedt (VMware) wrote:
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index c56fb57..669f23d 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -7989,14 +7989,14 @@ void sched_move_task(struct task_struct *tsk)
>  
>  	if (queued)
>  		dequeue_task(rq, tsk, DEQUEUE_SAVE | DEQUEUE_MOVE);
> -	if (unlikely(running))
> +	if (likely(running))
>  		put_prev_task(rq, tsk);
>  
>  	sched_change_group(tsk, TASK_MOVE_GROUP);
>  
>  	if (queued)
>  		enqueue_task(rq, tsk, ENQUEUE_RESTORE | ENQUEUE_MOVE);
> -	if (unlikely(running))
> +	if (likely(running))
>  		set_curr_task(rq, tsk);
>  
>  	task_rq_unlock(rq, tsk, &rf);


I prefer to simply remove the hint entirely and match all the other
instances of this pattern.

Now if only C wouldn't stink and have a sensible way to express this
pattern without having to copy/paste it all over :/