From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759638Ab3FNB7E (ORCPT ); Thu, 13 Jun 2013 21:59:04 -0400 Received: from szxga02-in.huawei.com ([119.145.14.65]:50560 "EHLO szxga02-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754759Ab3FNB6w (ORCPT ); Thu, 13 Jun 2013 21:58:52 -0400 Message-ID: <51BA7808.10004@huawei.com> Date: Fri, 14 Jun 2013 09:55:20 +0800 From: Li Zefan User-Agent: Mozilla/5.0 (Windows NT 6.1; rv:17.0) Gecko/20130509 Thunderbird/17.0.6 MIME-Version: 1.0 To: Andrew Morton CC: Tejun Heo , Glauber Costa , KAMEZAWA Hiroyuki , Johannes Weiner , LKML , Cgroups , , Michal Hocko Subject: [PATCH v4 7/9] memcg: don't need to get a reference to the parent References: <51BA7794.2000305@huawei.com> In-Reply-To: <51BA7794.2000305@huawei.com> Content-Type: text/plain; charset="GB2312" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.135.68.215] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The cgroup core guarantees it's always safe to access the parent. v2: - added a comment in mem_cgroup_put() as suggested by Michal - removed mem_cgroup_get(), otherwise gcc will warn that it's not used Signed-off-by: Li Zefan Acked-by: Michal Hocko Acked-by: KAMEZAWA Hiroyuki --- mm/memcontrol.c | 19 +++---------------- 1 file changed, 3 insertions(+), 16 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index a63d9f1..443fb45 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -513,7 +513,6 @@ enum res_type { */ static DEFINE_MUTEX(memcg_create_mutex); -static void mem_cgroup_get(struct mem_cgroup *memcg); static void mem_cgroup_put(struct mem_cgroup *memcg); static inline @@ -6210,19 +6209,10 @@ static void free_rcu(struct rcu_head *rcu_head) schedule_work(&memcg->work_freeing); } -static void mem_cgroup_get(struct mem_cgroup *memcg) -{ - atomic_inc(&memcg->refcnt); -} - static void __mem_cgroup_put(struct mem_cgroup *memcg, int count) { - if (atomic_sub_and_test(count, &memcg->refcnt)) { - struct mem_cgroup *parent = parent_mem_cgroup(memcg); + if (atomic_sub_and_test(count, &memcg->refcnt)) call_rcu(&memcg->rcu_freeing, free_rcu); - if (parent) - mem_cgroup_put(parent); - } } static void mem_cgroup_put(struct mem_cgroup *memcg) @@ -6325,12 +6315,9 @@ mem_cgroup_css_online(struct cgroup *cont) res_counter_init(&memcg->kmem, &parent->kmem); /* - * We increment refcnt of the parent to ensure that we can - * safely access it on res_counter_charge/uncharge. - * This refcnt will be decremented when freeing this - * mem_cgroup(see mem_cgroup_put). + * No need to take a reference to the parent because cgroup + * core guarantees its existence. */ - mem_cgroup_get(parent); } else { res_counter_init(&memcg->res, NULL); res_counter_init(&memcg->memsw, NULL); -- 1.8.0.2