From mboxrd@z Thu Jan 1 00:00:00 1970 From: One Thousand Gnomes Subject: Re: bit fields && data tearing Date: Mon, 8 Sep 2014 18:52:40 +0100 Message-ID: <20140908185240.21f52ca0@alan.etchedpixels.co.uk> References: <20140712181328.GA8738@redhat.com> <54079B70.4050200@hurleysoftware.com> <1409785893.30640.118.camel@pasglop> <063D6719AE5E284EB5DD2968C1650D6D17487172@AcuExch.aculab.com> <1409824374.4246.62.camel@pasglop> <5408E458.3@zytor.com> <54090AF4.7060406@hurleysoftware.com> <54091B30.7080100@zytor.com> <5409D76D.2070203@hurleysoftware.com> <5409D9C0.7030403@zytor.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <5409D9C0.7030403@zytor.com> Sender: linux-alpha-owner@vger.kernel.org To: "H. Peter Anvin" Cc: Peter Hurley , Benjamin Herrenschmidt , David Laight , Jakub Jelinek , "linux-arch@vger.kernel.org" , Tony Luck , "linux-ia64@vger.kernel.org" , Oleg Nesterov , "linux-kernel@vger.kernel.org" , Paul Mackerras , "Paul E. McKenney" , "linuxppc-dev@lists.ozlabs.org" , Miroslav Franc , Richard Henderson , linux-alpha@vger.kernel.org List-Id: linux-arch.vger.kernel.org On Fri, 05 Sep 2014 08:41:52 -0700 "H. Peter Anvin" wrote: > On 09/05/2014 08:31 AM, Peter Hurley wrote: > > > > Which is a bit ironic because I remember when Digital had a team > > working on emulating native x86 apps on Alpha/NT. > > > > Right, because the x86 architecture was obsolete and would never scale... Talking about "not scaling" can anyone explain how a "you need to use set_bit() and friends" bug report scaled into a hundred message plus discussion about ambiguous properties of processors (and nobody has audited all the embedded platforms we support yet, or the weirder ARMs) and a propsal to remove Alpha support. Wouldn't it be *much* simpler to do what I suggested in the first place and use the existing intended for purpose, deliberately put there, functions for atomic bitops, because they are fast on sane processors and they work on everything else. I think the whole "removing Alpha EV5" support is basically bonkers. Just use set_bit in the tty layer. Alpha will continue to work as well as it always has done and you won't design out support for any future processor that turns out not to do byte aligned stores. Alan From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from 251.110.2.81.in-addr.arpa ([81.2.110.251]:34125 "EHLO lxorguk.ukuu.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753006AbaIHRxd (ORCPT ); Mon, 8 Sep 2014 13:53:33 -0400 Date: Mon, 8 Sep 2014 18:52:40 +0100 From: One Thousand Gnomes Subject: Re: bit fields && data tearing Message-ID: <20140908185240.21f52ca0@alan.etchedpixels.co.uk> In-Reply-To: <5409D9C0.7030403@zytor.com> References: <20140712181328.GA8738@redhat.com> <54079B70.4050200@hurleysoftware.com> <1409785893.30640.118.camel@pasglop> <063D6719AE5E284EB5DD2968C1650D6D17487172@AcuExch.aculab.com> <1409824374.4246.62.camel@pasglop> <5408E458.3@zytor.com> <54090AF4.7060406@hurleysoftware.com> <54091B30.7080100@zytor.com> <5409D76D.2070203@hurleysoftware.com> <5409D9C0.7030403@zytor.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-arch-owner@vger.kernel.org List-ID: To: "H. Peter Anvin" Cc: Peter Hurley , Benjamin Herrenschmidt , David Laight , Jakub Jelinek , "linux-arch@vger.kernel.org" , Tony Luck , "linux-ia64@vger.kernel.org" , Oleg Nesterov , "linux-kernel@vger.kernel.org" , Paul Mackerras , "Paul E. McKenney" , "linuxppc-dev@lists.ozlabs.org" , Miroslav Franc , Richard Henderson , linux-alpha@vger.kernel.org Message-ID: <20140908175240.pOncVFceQixlzPjfee64Lj_Vh0qnQcsI_3kZja5ihxQ@z> On Fri, 05 Sep 2014 08:41:52 -0700 "H. Peter Anvin" wrote: > On 09/05/2014 08:31 AM, Peter Hurley wrote: > > > > Which is a bit ironic because I remember when Digital had a team > > working on emulating native x86 apps on Alpha/NT. > > > > Right, because the x86 architecture was obsolete and would never scale... Talking about "not scaling" can anyone explain how a "you need to use set_bit() and friends" bug report scaled into a hundred message plus discussion about ambiguous properties of processors (and nobody has audited all the embedded platforms we support yet, or the weirder ARMs) and a propsal to remove Alpha support. Wouldn't it be *much* simpler to do what I suggested in the first place and use the existing intended for purpose, deliberately put there, functions for atomic bitops, because they are fast on sane processors and they work on everything else. I think the whole "removing Alpha EV5" support is basically bonkers. Just use set_bit in the tty layer. Alpha will continue to work as well as it always has done and you won't design out support for any future processor that turns out not to do byte aligned stores. Alan