From: Li Zefan <lizefan@huawei.com>
Date: Sun, 9 Jun 2013 09:16:46 +0000 (+0800)
Subject: cpuset: allow to move tasks to empty cpusets
X-Git-Tag: omap-for-v3.11/fixes-for-merge-window~43^2~2
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=88fa523bff295f1d60244a54833480b02f775152;p=pandora-kernel.git

cpuset: allow to move tasks to empty cpusets

Currently some cpuset behaviors are not friendly when cpuset is co-mounted
with other cgroup controllers.

Now with this patchset if cpuset is mounted with sane_behavior option,
it behaves differently:

- Tasks will be kept in empty cpusets when hotplug happens and take
  masks of ancestors with non-empty cpus/mems, instead of being moved to
  an ancestor.

- A task can be moved into an empty cpuset, and again it takes masks of
  ancestors, so the user can drop a task into a newly created cgroup without
  having to do anything for it.

As tasks can reside in empy cpusets, here're some rules:

- They can be moved to another cpuset, regardless it's empty or not.

- Though it takes masks from ancestors, it takes other configs from the
  empty cpuset.

- If the ancestors' masks are changed, those tasks will also be updated
  to take new masks.

v2: add documentation in include/linux/cgroup.h

Signed-off-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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