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Date: Thu, 3 Mar 2016 14:01:43 +0530
Message-ID: <CAG53R5WVdahjdJRy=AJ3T2uw45ZZA2sYWGnHxLANzX6g7JWtiA@mail.gmail.com>
Subject: Re: [PATCHv9 1/3] rdmacg: Added rdma cgroup controller
From: Parav Pandit <pandit.parav@gmail.com>
To: Haggai Eran <haggaie@mellanox.com>
Cc: Tejun Heo <tj@kernel.org>, cgroups@vger.kernel.org,
        linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-rdma@vger.kernel.org, lizefan@huawei.com,
        Johannes Weiner <hannes@cmpxchg.org>,
        Doug Ledford <dledford@redhat.com>, Liran Liss <liranl@mellanox.com>,
        "Hefty, Sean" <sean.hefty@intel.com>,
        Jason Gunthorpe <jgunthorpe@obsidianresearch.com>,
        Jonathan Corbet <corbet@lwn.net>, james.l.morris@oracle.com,
        serge@hallyn.com, Or Gerlitz <ogerlitz@mellanox.com>,
        Matan Barak <matanb@mellanox.com>, raindel@mellanox.com,
        akpm@linux-foundation.org, linux-security-module@vger.kernel.org
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On Thu, Mar 3, 2016 at 1:44 PM, Haggai Eran <haggaie@mellanox.com> wrote:
> On 03/03/2016 05:18, Parav Pandit wrote:
>> On Thu, Mar 3, 2016 at 1:28 AM, Parav Pandit <pandit.parav@gmail.com> wrote:
>>> On Wed, Mar 2, 2016 at 11:09 PM, Tejun Heo <tj@kernel.org> wrote:
>>>> Nothing seems to prevent @cg from going away if this races with
>>>> @current being migrated to a different cgroup.  Have you run this with
>>>> lockdep and rcu debugging enabled?  This should have triggered a
>>>> warning.
>> I am able to reproduce this race. Looking into how to address it.
>
> If I understand correctly, task_css() requires rcu read lock being held.
> Is task_get_css() suitable here?

Yes. Its suitable if we continue with newer API to drop "num" entries.
Or I will have make minor modification to support that in cgroup.h.
There is no variation as task_get_css_many, but its minor change anyway.
I saw slept off yesterday night, saw today morning.
Will test over weekend and wait for Tejun's opinion if there is any.