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Subject: Re: [PATCH 2/6] move_task_off_dead_cpu: take rq->lock around
 select_fallback_rq()
From: Peter Zijlstra <peterz@infradead.org>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>, Ben Blum <bblum@google.com>,
       Jiri Slaby <jirislaby@gmail.com>, Lai Jiangshan <laijs@cn.fujitsu.com>,
       Li Zefan <lizf@cn.fujitsu.com>, Miao Xie <miaox@cn.fujitsu.com>,
       Paul Menage <menage@google.com>, "Rafael J. Wysocki" <rjw@sisk.pl>,
       Tejun Heo <tj@kernel.org>, linux-kernel@vger.kernel.org
In-Reply-To: <20100315091010.GA9131@redhat.com>
References: <20100315091010.GA9131@redhat.com>
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Date: Wed, 24 Mar 2010 16:41:24 +0100
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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

> +       if (needs_cpu)
> +               dest_cpu = select_fallback_rq(dead_cpu, p);