linux-kernel - Re: [PATCH -rt 2/5] Thread Migration Preemption

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Date:	Sun, 15 Jul 2007 00:48:41 +0400
From:	Oleg Nesterov <oleg@...sign.ru>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>,
	Steven Rostedt <rostedt@...dmis.org>,
	Christoph Lameter <clameter@....com>
Subject: Re: [PATCH -rt 2/5] Thread Migration Preemption - v2

On 07/14, Peter Zijlstra wrote:

> --- linux-2.6.orig/kernel/sched.c
> +++ linux-2.6/kernel/sched.c
> @@ -288,6 +288,7 @@ struct rq {
>  
>  	struct task_struct *migration_thread;
>  	struct list_head migration_queue;
> +	struct list_head delayed_migration_queue;
>  #endif

I think this could be simplified a bit.

delayed_migration_queue can be a local variable in migration_thread(), then

>  #ifdef CONFIG_SCHEDSTATS
> @@ -5623,6 +5624,11 @@ static int migration_thread(void *data)
>  		head = &rq->migration_queue;
>  
>  		if (list_empty(head)) {
> +			/*
> +			 * we got a wakeup, give the delayed list another shot.
> +			 */
> +			if (current->state != TASK_INTERRUPTIBLE)
> +				list_splice(&rq->delayed_migration_queue, head);

No need to check TASK_INTERRUPTIBLE, just do list_splice() unconditionally and
call schedule().

Oleg.

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