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Date: Tue, 16 Dec 2008 10:35:09 -0800
Message-ID: <6599ad830812161035q7becedf1u3d90f4064f9b0964@mail.gmail.com>
Subject: Re: [PATCH] sched: fix another race when reading /proc/sched_debug
From: Paul Menage <menage@google.com>
To: Li Zefan <lizf@cn.fujitsu.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>, Ingo Molnar <mingo@elte.hu>,
       Andrew Morton <akpm@linux-foundation.org>,
       LKML <linux-kernel@vger.kernel.org>,
       KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
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On Tue, Dec 16, 2008 at 4:55 AM, Li Zefan <lizf@cn.fujitsu.com> wrote:
>
> This avoids accessing a destroyed cgroup, but still race with cgroup_create.
> You sugguested call cgroup_create_dir() before calling subsystems' create()
> method.
>

I think that if we need a fix for 2.6.28 I'll just make cgroup_path()
check for a NULL dentry in the passed cgroup, rather than shuffling
any code around. That combined with a simple RCU free in
cgroup_diput() should do the trick - I think I'll leave the existing
synchronize_rcu() at the beginning of cgroup_diput() in case we need
it for more reasons than I originally mentioned in the comment there.

Paul
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