From mboxrd@z Thu Jan 1 00:00:00 1970 From: linas@austin.ibm.com (Linas Vepstas) Subject: Re: [PATCH v2] gianfar: Add I/O barriers when touching buffer descriptor ownership. Date: Fri, 4 May 2007 17:13:09 -0500 Message-ID: <20070504221309.GR6193@austin.ibm.com> References: <20070502195712.GA16541@ld0162-tx32.am.freescale.net> <4638F0C4.2000406@freescale.com> <4638F734.2040809@freescale.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Kumar Gala , netdev@vger.kernel.org, jgarzik@pobox.com, linuxppc-dev@ozlabs.org To: Scott Wood Return-path: Received: from e31.co.us.ibm.com ([32.97.110.149]:48819 "EHLO e31.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1031524AbXEDWNK (ORCPT ); Fri, 4 May 2007 18:13:10 -0400 Received: from d03relay02.boulder.ibm.com (d03relay02.boulder.ibm.com [9.17.195.227]) by e31.co.us.ibm.com (8.13.8/8.13.8) with ESMTP id l44MDAh6001433 for ; Fri, 4 May 2007 18:13:10 -0400 Received: from d03av01.boulder.ibm.com (d03av01.boulder.ibm.com [9.17.195.167]) by d03relay02.boulder.ibm.com (8.13.8/8.13.8/NCO v8.3) with ESMTP id l44MDACS174760 for ; Fri, 4 May 2007 16:13:10 -0600 Received: from d03av01.boulder.ibm.com (loopback [127.0.0.1]) by d03av01.boulder.ibm.com (8.12.11.20060308/8.13.3) with ESMTP id l44MD9VJ013339 for ; Fri, 4 May 2007 16:13:10 -0600 Content-Disposition: inline In-Reply-To: <4638F734.2040809@freescale.com> Sender: netdev-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Wed, May 02, 2007 at 03:40:20PM -0500, Scott Wood wrote: > > Well, Segher doesn't want me to use iobarrier (because it's not I/O). > Andy doesn't want me to use wmb() (because it's sync). I don't think > something like gfar_wmb() would be appropriate. So the remaining > options are either eieio(), ? Just curious... the original intent of eieio was to order I/O, such as MMIO; it has no effect on memory that isn't marked cache-inhibited or write-trhough or guarded. Has this changed? I guess I haven't kept up with the times ... is eieio now being used to provide some other kind of barrier? Is eieio providing some sort of SMP synchronization side-effect? Point being: if Segher doesn't let you "use iobarrier (because it's not I/O)", then I don't understand why eieio would work (since that's for io only). --linas