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Date: Fri, 21 Nov 2008 11:18:29 -0800
Message-ID: <6599ad830811211118kd410ce0o68db8249e60c8dd8@mail.gmail.com>
Subject: Re: [PATCH] cgroups: use task_lock() for access tsk->cgroups safe in 
	cgroup_clone()
From: Paul Menage <menage@google.com>
To: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       Linux Containers <containers@lists.linux-foundation.org>
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On Fri, Nov 21, 2008 at 12:49 AM, Lai Jiangshan <laijs@cn.fujitsu.com> wrote:
>
> use task_lock() protect tsk->cgroups and get_css_set(tsk->cgroups)
>
>
> Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>

Sounds reasonable, given the race with cgroup_exit()

Reviewed-by: Paul Menage <menage@google.com>

Thanks,

Paul

> ---
> diff --git a/kernel/cgroup.c b/kernel/cgroup.c
> index 358e775..ddc10ac 100644
> --- a/kernel/cgroup.c
> +++ b/kernel/cgroup.c
> @@ -2933,6 +2943,7 @@ int cgroup_clone(struct task_struct *tsk, struct cgroup_subsys *subsys,
>                mutex_unlock(&cgroup_mutex);
>                return 0;
>        }
> +       task_lock(tsk);
>        cg = tsk->cgroups;
>        parent = task_cgroup(tsk, subsys->subsys_id);
>
> @@ -2941,6 +2952,7 @@ int cgroup_clone(struct task_struct *tsk, struct cgroup_subsys *subsys,
>
>        /* Keep the cgroup alive */
>        get_css_set(cg);
> +       task_unlock(tsk);
>        mutex_unlock(&cgroup_mutex);
>
>        /* Now do the VFS work to create a cgroup */
>
>