From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx197.postini.com [74.125.245.197]) by kanga.kvack.org (Postfix) with SMTP id 427636B0002 for ; Fri, 29 Mar 2013 20:35:46 -0400 (EDT) Message-ID: <51563336.701@huawei.com> Date: Sat, 30 Mar 2013 08:35:02 +0800 From: Li Zefan MIME-Version: 1.0 Subject: Re: [PATCH] memcg: take reference before releasing rcu_read_lock References: <51556CE9.9060000@huawei.com> <5155718A.90108@parallels.com> In-Reply-To: <5155718A.90108@parallels.com> Content-Type: text/plain; charset="GB2312" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Glauber Costa Cc: Michal Hocko , KAMEZAWA Hiroyuki , Johannes Weiner , LKML , Cgroups , linux-mm@kvack.org, Andrew Morton 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? ;) > Theoretically, the race you describe seem real, and the fix is sound. > -- 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