From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeff Garzik Subject: Re: [PATCH] gianfar: Add I/O barriers when touching buffer descriptor ownership. Date: Thu, 17 May 2007 20:45:49 -0400 Message-ID: <464CF73D.9050505@garzik.org> References: <20070516200659.GA23548@ld0162-tx32.am.freescale.net> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, linuxppc-dev@ozlabs.org To: Scott Wood Return-path: Received: from srv5.dvmed.net ([207.36.208.214]:43551 "EHLO mail.dvmed.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755591AbXERApw (ORCPT ); Thu, 17 May 2007 20:45:52 -0400 In-Reply-To: <20070516200659.GA23548@ld0162-tx32.am.freescale.net> Sender: netdev-owner@vger.kernel.org List-Id: netdev.vger.kernel.org Scott Wood wrote: > The hardware must not see that is given ownership of a buffer until it is > completely written, and when the driver receives ownership of a buffer, > it must ensure that any other reads to the buffer reflect its final > state. Thus, I/O barriers are added where required. > > Without this patch, I have observed GCC reordering the setting of > bdp->length and bdp->status in gfar_new_skb. Hardware reordering > was also theoretically possible. > > Signed-off-by: Scott Wood > --- > I've added the requested comments to the source code about > the use of eieio(). Jeff, please consider for 2.6.22, as it > fixes a bug that has been observed. > > drivers/net/gianfar.c | 11 +++++++++++ > 1 files changed, 11 insertions(+), 0 deletions(-) applied