Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762821Ab3DCM6U (ORCPT ); Wed, 3 Apr 2013 08:58:20 -0400 Received: from mx2.parallels.com ([199.115.105.18]:36395 "EHLO mx2.parallels.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1761572Ab3DCM6T (ORCPT ); Wed, 3 Apr 2013 08:58:19 -0400 Message-ID: <515C2788.90907@parallels.com> Date: Wed, 3 Apr 2013 16:58:48 +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: , LKML , Cgroups , Tejun Heo , Michal Hocko , KAMEZAWA Hiroyuki , Johannes Weiner Subject: Re: [RFC][PATCH 1/7] memcg: use css_get in sock_update_memcg() References: <515BF233.6070308@huawei.com> <515BF249.50607@huawei.com> In-Reply-To: <515BF249.50607@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: 1564 Lines: 44 On 04/03/2013 01:11 PM, Li Zefan wrote: > Use css_get/css_put instead of mem_cgroup_get/put. > > Note, if at the same time someone is moving @current to a different > cgroup and removing the old cgroup, css_tryget() may return false, > and sock->sk_cgrp won't be initialized. > > Signed-off-by: Li Zefan > --- > mm/memcontrol.c | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 23d0f6e..43ca91d 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -536,15 +536,15 @@ void sock_update_memcg(struct sock *sk) > */ > if (sk->sk_cgrp) { > BUG_ON(mem_cgroup_is_root(sk->sk_cgrp->memcg)); > - mem_cgroup_get(sk->sk_cgrp->memcg); > + css_get(&sk->sk_cgrp->memcg->css); > return; > } > > rcu_read_lock(); > memcg = mem_cgroup_from_task(current); > cg_proto = sk->sk_prot->proto_cgroup(memcg); > - if (!mem_cgroup_is_root(memcg) && memcg_proto_active(cg_proto)) { > - mem_cgroup_get(memcg); > + if (!mem_cgroup_is_root(memcg) && > + memcg_proto_active(cg_proto) && css_tryget(&memcg->css)) { > sk->sk_cgrp = cg_proto; > } What happens if this tryget fails ? Won't we leak a reference here? We will put regardless when the socket is released, and this may go negative. No? -- 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/