linux-kernel - Re: Bug in scheduler when using rt

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Message-ID: <1295419041.8017.120.camel@marge.simson.net>
Date:	Wed, 19 Jan 2011 07:37:21 +0100
From:	Mike Galbraith <efault@....de>
To:	Yong Zhang <yong.zhang0@...il.com>
Cc:	Peter Zijlstra <peterz@...radead.org>, samu.p.onkalo@...ia.com,
	mingo@...e.hu,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	tglx <tglx@...utronix.de>
Subject: Re: Bug in scheduler when using rt_mutex

On Wed, 2011-01-19 at 14:09 +0800, Yong Zhang wrote:
> On Wed, Jan 19, 2011 at 1:40 PM, Mike Galbraith <efault@....de> wrote:
> > On Wed, 2011-01-19 at 12:35 +0800, Yong Zhang wrote:
> >
> >> cfs_rq->curr != se is always true.
> >
> > If that were always true, we'd illegally enqueue a running task.
> 
> I'm sorry that I'm not express myself correctly.

Human communication methods are all buggy as hell :)

> The conclusion of (cfs_rq->curr != se is always true) is not
> self-contained. IOW, it's based on one condition which is
> (task_of(se) != rq->curr). So what I want to say is:
> task_of(se) != rq->curr    ==>   cfs_rq_of(se)->curr != se
> So,
>          !running                   ==>   cfs_rq_of(se)->curr != se
> 
> Is this more clear?

Yeah.

	-Mike

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