From mboxrd@z Thu Jan 1 00:00:00 1970 From: olof@lixom.net (Olof Johansson) Subject: Re: [PATCH v2] gianfar: Add I/O barriers when touching buffer descriptor ownership. Date: Fri, 4 May 2007 18:24:51 -0500 Message-ID: <20070504232451.GA15433@lixom.net> References: <20070502195712.GA16541@ld0162-tx32.am.freescale.net> <4638F0C4.2000406@freescale.com> <4638F734.2040809@freescale.com> <20070504221309.GR6193@austin.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, jgarzik@pobox.com, linuxppc-dev@ozlabs.org To: Linas Vepstas Return-path: Content-Disposition: inline In-Reply-To: <20070504221309.GR6193@austin.ibm.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: linuxppc-dev-bounces+glppd-linuxppc64-dev=m.gmane.org@ozlabs.org Errors-To: linuxppc-dev-bounces+glppd-linuxppc64-dev=m.gmane.org@ozlabs.org List-Id: netdev.vger.kernel.org On Fri, May 04, 2007 at 05:13:09PM -0500, Linas Vepstas wrote: > 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). Eieio has always worked for regular cachable memory as well, it just never orders _between_ cache inhibited/guarded and cachable memory. Book II 2.03 has a pretty good description of it on page 367. -Olof