From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx155.postini.com [74.125.245.155]) by kanga.kvack.org (Postfix) with SMTP id 7BB5A6B0005 for ; Thu, 4 Apr 2013 11:34:27 -0400 (EDT) Date: Thu, 4 Apr 2013 17:34:25 +0200 From: Michal Hocko Subject: Re: [RFC][PATCH 6/7] memcg: don't need to get a reference to the parent Message-ID: <20130404153425.GN29911@dhcp22.suse.cz> References: <515BF233.6070308@huawei.com> <515BF2B1.9060909@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <515BF2B1.9060909@huawei.com> Sender: owner-linux-mm@kvack.org List-ID: To: Li Zefan Cc: linux-mm@kvack.org, LKML , Cgroups , Tejun Heo , Glauber Costa , KAMEZAWA Hiroyuki , Johannes Weiner On Wed 03-04-13 17:13:21, Li Zefan wrote: > The cgroup core guarantees it's always safe to access the parent. > > Signed-off-by: Li Zefan I would just prefer if you put a comment into place where we used to take a reference to parent so that it is more obvious in the code. See bellow. Acked-by: Michal Hocko > --- > mm/memcontrol.c | 14 +------------- > 1 file changed, 1 insertion(+), 13 deletions(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index ad576e8..45129cd 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -6124,12 +6124,8 @@ static void mem_cgroup_get(struct mem_cgroup *memcg) > > 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) > @@ -6229,14 +6225,6 @@ mem_cgroup_css_online(struct cgroup *cont) > res_counter_init(&memcg->res, &parent->res); > res_counter_init(&memcg->memsw, &parent->memsw); > 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). > - */ > - mem_cgroup_get(parent); Maybe a little note would be nice /* * No need to take reference to parent because cgroup * core guarantees its existence */ > } else { > res_counter_init(&memcg->res, NULL); > res_counter_init(&memcg->memsw, NULL); > -- > 1.8.0.2 > > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to majordomo@kvack.org. For more info on Linux MM, > see: http://www.linux-mm.org/ . > Don't email: email@kvack.org -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org