cgroup: improve old cgroup handling in cgroup_attach_proc()
authorTejun Heo <tj@kernel.org>
Tue, 13 Dec 2011 02:12:21 +0000 (18:12 -0800)
committerTejun Heo <tj@kernel.org>
Tue, 13 Dec 2011 02:12:21 +0000 (18:12 -0800)
commit134d33737f9015761c3832f6b268fae6274aac7f
tree536b973af6429c25e1fc8ccbaf76395c09a8623d
parentcd3d095275374220921fcf0d4e0c16584b26ddbc
cgroup: improve old cgroup handling in cgroup_attach_proc()

cgroup_attach_proc() behaves differently from cgroup_attach_task() in
the following aspects.

* All hooks are invoked even if no task is actually being moved.

* ->can_attach_task() is called for all tasks in the group whether the
  new cgrp is different from the current cgrp or not; however,
  ->attach_task() is skipped if new equals new.  This makes the calls
  asymmetric.

This patch improves old cgroup handling in cgroup_attach_proc() by
looking up the current cgroup at the head, recording it in the flex
array along with the task itself, and using it to remove the above two
differences.  This will also ease further changes.

-v2: nr_todo renamed to nr_migrating_tasks as per Paul Menage's
     suggestion.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reviewed-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Paul Menage <paul@paulmenage.org>
Acked-by: Li Zefan <lizf@cn.fujitsu.com>
kernel/cgroup.c