From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx156.postini.com [74.125.245.156]) by kanga.kvack.org (Postfix) with SMTP id 3B4AD6B0006 for ; Tue, 2 Apr 2013 04:06:35 -0400 (EDT) Message-ID: <515A91B4.3090607@parallels.com> Date: Tue, 2 Apr 2013 12:07:16 +0400 From: Glauber Costa MIME-Version: 1.0 Subject: Re: [PATCH] memcg: don't do cleanup manually if mem_cgroup_css_online() fails References: <515A8A40.6020406@huawei.com> <515A90ED.7010208@huawei.com> In-Reply-To: <515A90ED.7010208@huawei.com> Content-Type: text/plain; charset="GB2312" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Li Zefan Cc: Michal Hocko , Johannes Weiner , KAMEZAWA Hiroyuki , LKML , Cgroups , linux-mm@kvack.org On 04/02/2013 12:03 PM, Li Zefan wrote: > On 2013/4/2 15:35, Li Zefan wrote: >> If memcg_init_kmem() returns -errno when a memcg is being created, >> mem_cgroup_css_online() will decrement memcg and its parent's refcnt, > >> (but strangely there's no mem_cgroup_put() for mem_cgroup_get() called >> in memcg_propagate_kmem()). > > The comment in memcg_propagate_kmem() suggests it knows mem_cgroup_css_free() > will be called in failure, while mem_cgroup_css_online() doesn't know. > This is a bit suspicious. At first your analysis seems fair, but I've extensively tested memcg teardown process with kmemcg (and even uncovered some bugs at that), and it works when and how expected. Also, note that this teardown code long predates kmemcg. I am not saying your are wrong - on the contrary, you seem to be right, but I think this one needs to be handled with extra care. I will run some tests, take a look, and get back to you. -- 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