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

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Message-Id: <1184446418.5284.86.camel@lappy>
Date:	Sat, 14 Jul 2007 22:53:38 +0200
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Oleg Nesterov <oleg@...sign.ru>
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 Sun, 2007-07-15 at 00:48 +0400, Oleg Nesterov wrote:
> 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().

Yes, I got my head in a twist on that one. You are quite right!

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