linux-kernel - Re: [PATCH v3] cgroup: fix cgroup

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Message-ID: <20130218171756.GE17414@htj.dyndns.org>
Date:	Mon, 18 Feb 2013 09:17:56 -0800
From:	Tejun Heo <tj@...nel.org>
To:	Li Zefan <lizefan@...wei.com>
Cc:	"Kirill A. Shutemov" <kirill@...temov.name>,
	LKML <linux-kernel@...r.kernel.org>,
	Cgroups <cgroups@...r.kernel.org>
Subject: Re: [PATCH v3] cgroup: fix cgroup_rmdir() vs close(eventfd) race

On Mon, Feb 18, 2013 at 06:56:14PM +0800, Li Zefan wrote:
> commit 205a872bd6f9a9a09ef035ef1e90185a8245cc58 ("cgroup: fix lockdep
> warning for event_control") solved a deadlock by introducing a new
> bug.
> 
> Move cgrp->event_list to a temporary list doesn't mean you can traverse
> this list locklessly, because at the same time cgroup_event_wake() can
> be called and remove the event from the list. The result of this race
> is disastrous.
> 
> We adopt the way how kvm irqfd code implements race-free event removal,
> which is now described in the comments in cgroup_event_wake().
> 
> v3:
> - call eventfd_signal() no matter it's eventfd close or cgroup removal
> that removes the cgroup event.
> 
> Acked-by: Kirill A. Shutemov <kirill@...temov.name>
> Signed-off-by: Li Zefan <lizefan@...wei.com>

Dropped v2 and applied this one to cgroup/for-3.9.

Thanks.

-- 
tejun
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