From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Paul Menage <menage@google.com>, Li Zefan <lizf@cn.fujitsu.com>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH RESEND] cgroups: fix incorrect using rcu_dereference() in cgroup_subsys_state()
Date: Tue, 4 Jan 2011 13:23:57 -0800 [thread overview]
Message-ID: <20110104212357.GU2026@linux.vnet.ibm.com> (raw)
In-Reply-To: <4D22D7BE.4070702@cn.fujitsu.com>
On Tue, Jan 04, 2011 at 04:18:06PM +0800, Lai Jiangshan wrote:
> From: Li Zefan <lizf@cn.fujitsu.com>
> Date: Mon, 25 Aug 2008 11:05:28 +0800
> (Original) Subject: [PATCH] cgroup: fix wrong rcu_dereference()
>
> It is tsk->cgroups which is protected by RCU, not ->subsys[subsys_id].
>
> laijs: updated it(the surrounding code have been changed since these two years).
This looks plausible to me, assuming that the cgroups guys are OK with
it.
One requested change: could you please delete the rcu_read_lock_held()?
This is now implied by rcu_dereference_check(). With that:
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
> Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
> ---
> diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
> index ed4ba11..a798814 100644
> --- a/include/linux/cgroup.h
> +++ b/include/linux/cgroup.h
> @@ -535,10 +535,11 @@ static inline struct cgroup_subsys_state *cgroup_subsys_state(
> * cgroup_subsys::attach() methods.
> */
> #define task_subsys_state_check(task, subsys_id, __c) \
> - rcu_dereference_check(task->cgroups->subsys[subsys_id], \
> + rcu_dereference_check(task->cgroups, \
> rcu_read_lock_held() || \
> lockdep_is_held(&task->alloc_lock) || \
> - cgroup_lock_is_held() || (__c))
> + cgroup_lock_is_held() || \
> + (__c))->subsys[subsys_id]
>
> static inline struct cgroup_subsys_state *
> task_subsys_state(struct task_struct *task, int subsys_id)
next prev parent reply other threads:[~2011-01-04 21:24 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-01-04 8:18 [PATCH RESEND] cgroups: fix incorrect using rcu_dereference() in cgroup_subsys_state() Lai Jiangshan
2011-01-04 21:23 ` Paul E. McKenney [this message]
2011-01-05 1:31 ` Paul Menage
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