netdev - Re: [PATCH 1/3] don't attach a task to a dead cgroup

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Message-ID: <20120419225322.GC10553@google.com>
Date:	Thu, 19 Apr 2012 15:53:22 -0700
From:	Tejun Heo <tj@...nel.org>
To:	Glauber Costa <glommer@...allels.com>
Cc:	netdev@...r.kernel.org, cgroups@...r.kernel.org,
	Li Zefan <lizefan@...wei.com>, kamezawa.hiroyu@...fujitsu.com,
	David Miller <davem@...emloft.net>, devel@...nvz.org
Subject: Re: [PATCH 1/3] don't attach a task to a dead cgroup

On Thu, Apr 19, 2012 at 07:49:16PM -0300, Glauber Costa wrote:
> Not all external callers of cgroup_attach_task() test to
> see if the cgroup is still live - the internal callers at
> cgroup.c does.
> 
> With this test in cgroup_attach_task, we can assure that
> no tasks are ever moved to a cgroup that is past its
> destruction point and was already marked as dead.
> 
> Signed-off-by: Glauber Costa <glommer@...allels.com>
> CC: Tejun Heo <tj@...nel.org>
> CC: Li Zefan <lizefan@...wei.com>
> CC: Kamezawa Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> ---
>  kernel/cgroup.c |    3 +++
>  1 files changed, 3 insertions(+), 0 deletions(-)
> 
> diff --git a/kernel/cgroup.c b/kernel/cgroup.c
> index b61b938..932c318 100644
> --- a/kernel/cgroup.c
> +++ b/kernel/cgroup.c
> @@ -1927,6 +1927,9 @@ int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
>  	struct cgroup_taskset tset = { };
>  	struct css_set *newcg;
>  
> +	if (cgroup_is_removed(cgrp))
> +		return -ENODEV;
> +

Isn't the test in cgroup_lock_live_group() enough?

-- 
tejun
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