From mboxrd@z Thu Jan 1 00:00:00 1970 From: Glauber Costa Subject: Re: [PATCH] memcg: take reference before releasing rcu_read_lock Date: Mon, 1 Apr 2013 11:24:13 +0400 Message-ID: <5159361D.40302@parallels.com> References: <51556CE9.9060000@huawei.com> <5155718A.90108@parallels.com> <51563336.701@huawei.com> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <51563336.701@huawei.com> Sender: owner-linux-mm@kvack.org List-ID: Content-Type: text/plain; charset="us-ascii" To: Li Zefan Cc: Michal Hocko , KAMEZAWA Hiroyuki , Johannes Weiner , LKML , Cgroups , linux-mm@kvack.org, Andrew Morton On 03/30/2013 04:35 AM, Li Zefan wrote: > On 2013/3/29 18:48, Glauber Costa wrote: >> On 03/29/2013 02:28 PM, Li Zefan wrote: >>> The memcg is not referenced, so it can be destroyed at anytime right >>> after we exit rcu read section, so it's not safe to access it. >>> >>> To fix this, we call css_tryget() to get a reference while we're still >>> in rcu read section. >>> >>> This also removes a bogus comment above __memcg_create_cache_enqueue(). >>> >> Out of curiosity, did you see that happening ? >> > > Just by code inspection. This is not the only place you use RCU in this > wrong way. Remember the last patch I sent? ;) > Indeed, that is what happens with miscomprehensions: the mistake tends to be repeated. Thanks for your diligence with this. -- 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