From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tom Tucker Subject: Re: [RFC,PATCH 11/15] knfsd: RDMA transport core Date: Mon, 21 May 2007 11:02:05 -0500 Message-ID: <1179763325.23385.244.camel@trinity.ogc.int> References: <1179510352.23385.123.camel@trinity.ogc.int> <1179515255.6488.136.camel@heimdal.trondhjem.org> <1179518863.23385.195.camel@trinity.ogc.int> <18001.18232.387141.533217@notabene.brown> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Cc: Tom Talpey , Linux NFS Mailing List , Peter Leckie , Greg Banks , Trond Myklebust To: Neil Brown Return-path: Received: from sc8-sf-mx1-b.sourceforge.net ([10.3.1.91] helo=mail.sourceforge.net) by sc8-sf-list2-new.sourceforge.net with esmtp (Exim 4.43) id 1HqAKn-0007Xn-G1 for nfs@lists.sourceforge.net; Mon, 21 May 2007 09:02:09 -0700 Received: from rrcs-71-42-183-126.sw.biz.rr.com ([71.42.183.126] helo=smtp.opengridcomputing.com) by mail.sourceforge.net with esmtp (Exim 4.44) id 1HqAKq-00044M-20 for nfs@lists.sourceforge.net; Mon, 21 May 2007 09:02:12 -0700 In-Reply-To: <18001.18232.387141.533217@notabene.brown> List-Id: "Discussion of NFS under Linux development, interoperability, and testing." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: nfs-bounces@lists.sourceforge.net Errors-To: nfs-bounces@lists.sourceforge.net On Mon, 2007-05-21 at 17:16 +1000, Neil Brown wrote: > On Friday May 18, tom@opengridcomputing.com wrote: > > On Fri, 2007-05-18 at 15:07 -0400, Trond Myklebust wrote: > > > > > > + while (xprt->sc_ctxt_cnt < target) { > > > > + xprt->sc_ctxt_cnt ++; > > > > + spin_unlock_irqrestore(&xprt->sc_ctxt_lock, flags); > > > > + > > > > + ctxt = kmalloc(sizeof(*ctxt), GFP_KERNEL); > > > > + > > > > + spin_lock_irqsave(&xprt->sc_ctxt_lock, flags); > > > > > > You've now dropped the spinlock. How can you know that the condition > > > xprt->sc_ctxt_cnt <= target is still valid? > > > > > > > I increment the sc_ctxt_cnt with the lock held. If I'm at the limit, the > > competing thread will find it equal -- correct? > > > > I'm having trouble figuring out who the competing thread is. > As far as I can see (Well... "have seen"), this is always called from > the context of an nfsd thread which has sole access to the xprt. So > there is no race. > ?? The callback handler for SQ CQ (send queue completion queue) is called on interrupt context. This function returns contexts to this queue when cleaning up completed SQ WR (send queue work requests). See sq_cq_reap in svc_rdma_transport.c, line #329. > > NeilBrown ------------------------------------------------------------------------- This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. No limits. Just data. Click to get it now. http://sourceforge.net/powerbar/db2/ _______________________________________________ NFS maillist - NFS@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/nfs