From 5300a9b3482b6d9c32de6d5f4eaeab0fbafa70a8 Mon Sep 17 00:00:00 2001
From: Tejun Heo <tj@kernel.org>
Date: Fri, 9 Nov 2012 09:12:30 -0800
Subject: [PATCH] cgroup_freezer: add ->post_create() and ->pre_destroy() and
 track online state

A cgroup is online and visible to iteration between ->post_create()
and ->pre_destroy().  This patch introduces CGROUP_FREEZER_ONLINE and
toggles it from the newly added freezer_post_create() and
freezer_pre_destroy() while holding freezer->lock such that a
cgroup_freezer can be reilably distinguished to be online.  This will
be used by full hierarchy support.

ONLINE test is added to freezer_apply_state() but it currently doesn't
make any difference as freezer_write() can only be called for an
online cgroup.

Adjusting system_freezing_cnt on destruction is moved from
freezer_destroy() to the new freezer_pre_destroy() for consistency.

This patch doesn't introduce any noticeable behavior change.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
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