From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751993Ab1ITOiy (ORCPT ); Tue, 20 Sep 2011 10:38:54 -0400 Received: from mx2.netapp.com ([216.240.18.37]:29053 "EHLO mx2.netapp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751643Ab1ITOiw (ORCPT ); Tue, 20 Sep 2011 10:38:52 -0400 X-IronPort-AV: E=Sophos;i="4.68,411,1312182000"; d="scan'208";a="583299582" X-MimeOLE: Produced By Microsoft Exchange V6.5 Content-class: urn:content-classes:message MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Subject: RE: [PATCH v4 1/8] SUNRPC: introduce helpers for reference counted rpcbind clients Date: Tue, 20 Sep 2011 07:38:53 -0700 Message-ID: <2E1EB2CF9ED1CB4AA966F0EB76EAB4430B47FD2B@SACMVEXC2-PRD.hq.netapp.com> In-reply-to: <4E78A4AF.1020303@parallels.com> X-MS-Has-Attach: X-MS-TNEF-Correlator: Thread-Topic: [PATCH v4 1/8] SUNRPC: introduce helpers for reference counted rpcbind clients Thread-Index: Acx3oqFmBa7xtCIPQLWVb5tVto9UlQAADCPQ 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> <4E78A4AF.1020303@parallels.com> From: "Myklebust, Trond" To: "Stanislav Kinsbursky" Cc: "Schumaker, Bryan" , , "Pavel Emelianov" , , , , , X-OriginalArrivalTime: 20 Sep 2011 14:38:51.0973 (UTC) FILETIME=[0423C750:01CC77A3] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from base64 to 8bit by nfs id p8KEd0vf021166 > -----Original Message----- > From: Stanislav Kinsbursky [mailto:skinsbursky@parallels.com] > Sent: Tuesday, September 20, 2011 10:35 AM > 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 > > 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? Yes, and so you don't need an smp_rmb() on the reader side. However, you still need to ensure that the processor which _sets_ the rpcb_users and rpcb_local_clnt/4 actually writes them in the correct order. Cheers Trond {.n++%ݶw{.n+{G{ayʇڙ,jfhz_(階ݢj"mG?&~iOzv^m ?I