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Subject: Re: [PATCH 04/10] Display /proc/stat information per cgroup
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: Glauber Costa <glommer@parallels.com>
Cc: linux-kernel@vger.kernel.org, paul@paulmenage.org, lizf@cn.fujitsu.com,
        daniel.lezcano@free.fr, jbottomley@parallels.com
Date: Wed, 05 Oct 2011 10:56:05 +0200
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On Sun, 2011-10-02 at 23:21 +0400, Glauber Costa wrote:
> +struct kernel_stat *task_group_kstat(struct task_struct *p)
> +{
> +       struct task_group *tg;
> +       struct kernel_stat *kstat;
> +
> +       rcu_read_lock();
> +       tg = task_group(p);
> +       kstat = tg->cpustat;
> +       rcu_read_unlock();
> +       return kstat;
> +} 

Who keeps tg alive and kicking while you poke at its (cpustat) member?