linux-kernel - Re: [PATCH 2/6] move_task_off_dead_cpu: take rq->lock around select_fallback

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Date:	Wed, 24 Mar 2010 17:17:02 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Ingo Molnar <mingo@...e.hu>, Ben Blum <bblum@...gle.com>,
	Jiri Slaby <jirislaby@...il.com>,
	Lai Jiangshan <laijs@...fujitsu.com>,
	Li Zefan <lizf@...fujitsu.com>,
	Miao Xie <miaox@...fujitsu.com>,
	Paul Menage <menage@...gle.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>, Tejun Heo <tj@...nel.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/6] move_task_off_dead_cpu: take rq->lock around
 select_fallback_rq()

On Wed, 2010-03-24 at 17:07 +0100, Oleg Nesterov wrote:
> On 03/24, Peter Zijlstra wrote:
> >
> > On Mon, 2010-03-15 at 10:10 +0100, Oleg Nesterov wrote:
> > >  static void move_task_off_dead_cpu(int dead_cpu, struct task_struct *p)
> > >  {
> > > +       struct rq *rq = cpu_rq(dead_cpu);
> > > +       int needs_cpu, dest_cpu;
> > > +       unsigned long flags;
> > >  again:
> > > +       local_irq_save(flags);
> > > +
> > > +       raw_spin_lock(&rq->lock);
> > > +       needs_cpu = (task_cpu(p) == dead_cpu) && (p->state != TASK_WAKING);
> >
> >                                        ^ 
> > kernel/sched.c:5445: warning: ‘dest_cpu’ may be used uninitialized in this function
> 
> Hmm. looks like my gcc is more friendly...

Hrm, that and I'm apparently unable to read, it said dest_cpu, not
dead_cpu.. a well, I'll slam an __maybe_unused in.

> OK. certainly I'll send the updated patch, if this series passes
> your review otherwise.

Yeah, you made a few good points in 0/6, am now staring at the code on
how to close those holes, hope to post something sensible soon.
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