Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754043Ab3C2KsG (ORCPT ); Fri, 29 Mar 2013 06:48:06 -0400 Received: from mx2.parallels.com ([199.115.105.18]:43490 "EHLO mx2.parallels.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753051Ab3C2KsE (ORCPT ); Fri, 29 Mar 2013 06:48:04 -0400 Message-ID: <5155718A.90108@parallels.com> Date: Fri, 29 Mar 2013 14:48:42 +0400 From: Glauber Costa User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130311 Thunderbird/17.0.4 MIME-Version: 1.0 To: Li Zefan CC: Michal Hocko , KAMEZAWA Hiroyuki , Johannes Weiner , LKML , Cgroups , , Andrew Morton Subject: Re: [PATCH] memcg: take reference before releasing rcu_read_lock References: <51556CE9.9060000@huawei.com> In-Reply-To: <51556CE9.9060000@huawei.com> Content-Type: text/plain; charset="GB2312" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 767 Lines: 19 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 ? Theoretically, the race you describe seem real, and the fix is sound. Acked-by: Glauber Costa -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/