Return-Path: Received: from mailhub.sw.ru ([195.214.232.25]:16220 "EHLO relay.sw.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751614Ab1ITOgH (ORCPT ); Tue, 20 Sep 2011 10:36:07 -0400 Message-ID: <4E78A4AF.1020303@parallels.com> Date: Tue, 20 Sep 2011 18:35:27 +0400 From: Stanislav Kinsbursky To: "Myklebust, Trond" CC: "Schumaker, Bryan" , "linux-nfs@vger.kernel.org" , Pavel Emelianov , "neilb@suse.de" , "netdev@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "bfields@fieldses.org" , "davem@davemloft.net" Subject: Re: [PATCH v4 1/8] SUNRPC: introduce helpers for reference counted rpcbind clients References: <20110920101031.9861.18444.stgit@localhost6.localdomain6> <20110920101341.9861.51453.stgit@localhost6.localdomain6> <4E788F8C.20103@netapp.com> <2E1EB2CF9ED1CB4AA966F0EB76EAB4430B47FD10@SACMVEXC2-PRD.hq.netapp.com> <4E789679.1060601@parallels.com> <2E1EB2CF9ED1CB4AA966F0EB76EAB4430B47FD22@SACMVEXC2-PRD.hq.netapp.com> In-Reply-To: <2E1EB2CF9ED1CB4AA966F0EB76EAB4430B47FD22@SACMVEXC2-PRD.hq.netapp.com> Content-Type: text/plain; charset=UTF-8; format=flowed Sender: linux-nfs-owner@vger.kernel.org List-ID: MIME-Version: 1.0 20.09.2011 18:14, Myklebust, Trond пишет: >>> >>> Doesn't it need to be protected by rpcb_clnt_lock too? >>> >> >> Nope from my pow. It's protected by rpcb_create_local_mutex. I.e. no one >> will change rpcb_users since it's zero. If it's non zero - we willn't get to >> rpcb_set_local(). > > OK, so you are saying that the rpcb_users++ below could be replaced by rpcb_users=1? > Yes, you right. > In that case, don't you need a smp_wmb() between the setting of rpcb_local_clnt/4 and the setting of rpcb_users? Otherwise, how do you guarantee that rpcb_users != 0 implies rpbc_local_clnt/4 != NULL? > We check rpcb_users under spinlock. Gain spinlock forces memory barrier, doesn't it? -- Best regards, Stanislav Kinsbursky