Date: Thu, 3 Dec 2015 10:16:32 -0500
From: Tejun Heo <tj@kernel.org>
To: Li Zefan <lizefan@huawei.com>, Daniel Wagner <daniel.wagner@bmw-carit.de>
Cc: Johannes Weiner <hannes@cmpxchg.org>, cgroups@vger.kernel.org,
        linux-kernel@vger.kernel.org, Dave Jones <davej@codemonkey.org.uk>,
        kernel-team@fb.com, Aleksa Sarai <cyphar@cyphar.com>,
        Michal Hocko <mhocko@kernel.org>, Ingo Molnar <mingo@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Neil Horman <nhorman@tuxdriver.com>
Subject: Re: [PATCH cgroup/for-4.4-fixes 2/3] cgroup: fix handling of
 multi-destination migration from subtree_control enabling
Message-ID: <20151203151632.GE27463@mtj.duckdns.org>
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 <20151124144418.GB17033@mtj.duckdns.org>
 <56547B22.2020802@bmw-carit.de>
 <20151124145945.GF17033@mtj.duckdns.org>
 <20151130224205.GA9039@mtj.duckdns.org>
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On Mon, Nov 30, 2015 at 05:44:31PM -0500, Tejun Heo wrote:
> From 0d7d444e260493252e30c70813c7657e9ede2f12 Mon Sep 17 00:00:00 2001
> From: Tejun Heo <tj@kernel.org>
> Date: Mon, 30 Nov 2015 17:24:34 -0500
> 
> Consider the following v2 hierarchy.
> 
>   P0 (+memory) --- P1 (-memory) --- A
>                                  \- B
> 
> P0 has memory enabled in its subtree_control while P1 doesn't.  If
> both A and B contain processes, they would belong to the memory css of
> P1.  Now if memory is enabled on P1's subtree_control, memory csses
> should be created on both A and B and A's processes should be moved to
> the former and B's processes the latter.  IOW, enabling controllers
> can cause atomic migrations into different csses.
> 
> The core cgroup migration logic has been updated accordingly but the
> controller migration methods haven't and still assume that all tasks
> migrate to a single target css; furthermore, the methods were fed the
> css in which subtree_control was updated which is the parent of the
> target csses.  pids controller depends on the migration methods to
> move charges and this made the controller attribute charges to the
> wrong csses often triggering the following warning by driving a
> counter negative.

Applying 1-2 to libata/for-4.4-fixes.

Thanks.

-- 
tejun
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