From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michael Cree Subject: Re: bit fields && data tearing Date: Fri, 5 Sep 2014 20:16:48 +1200 Message-ID: <20140905081648.GB5281@omega> 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> <54091B30.2090509@zytor.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Return-path: Content-Disposition: inline In-Reply-To: <54091B30.2090509@zytor.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: linuxppc-dev-bounces+glppe-linuxppc-embedded-2=m.gmane.org@lists.ozlabs.org Sender: "Linuxppc-dev" To: "H. Peter Anvin" Cc: Jakub Jelinek , "linux-arch@vger.kernel.org" , Tony Luck , "linux-ia64@vger.kernel.org" , Peter Hurley , Oleg Nesterov , "linux-kernel@vger.kernel.org" , David Laight , Paul Mackerras , linux-alpha@vger.kernel.org, "Paul E. McKenney" , "linuxppc-dev@lists.ozlabs.org" , Miroslav Franc , Richard Henderson List-Id: linux-arch.vger.kernel.org T24gVGh1LCBTZXAgMDQsIDIwMTQgYXQgMDc6MDg6NDhQTSAtMDcwMCwgSC4gUGV0ZXIgQW52aW4g d3JvdGU6Cj4gT24gMDkvMDQvMjAxNCAwNTo1OSBQTSwgUGV0ZXIgSHVybGV5IHdyb3RlOgo+ID4g SSBoYXZlIG5vIGlkZWEgaG93IHByZXZhbGVudCB0aGUgZXY1NiBpcyBjb21wYXJlZCB0byB0aGUg ZXY1Lgo+ID4gU3RpbGwgd2UncmUgdGFsa2luZyBhYm91dCBhIGNoaXAgdGhhdCBjYW1lIG91dCBp biAxOTk2Lgo+IAo+IEFoIHllcywgSSBzdGFuZCBjb3JyZWN0ZWQuICBBY2NvcmRpbmcgdG8gV2lr aXBlZGlhLCB0aGUgYWZmZWN0ZWQgQ1BVcwo+IHdlcmUgYWxsIHRoZSAyMTA2eCBDUFVzIChFVjQs IEVWNDUsIExDQTQsIExDQTQ1KSBwbHVzIHRoZSAyMTE2NCB3aXRoIG5vCj4gc3VmZml4IChFVjUp LiAgSG93ZXZlciwgd2UncmUgc3RpbGwgdGFsa2luZyBhYm91dCBtdXNldW0gcGllY2VzIGhlcmUu CgpZZXMsIHRoYXQgaXMgY29ycmVjdCwgRVY1NiBpcyB0aGUgZmlyc3QgQWxwaGEgQ1BVIHRvIGhh dmUgdGhlIGJ5dGUtd29yZApleHRlbnNpb24gKEJXWCkgQ1BVIGluc3RydWN0aW9ucy4KCkl0IHdv dWxkIG5vdCB3b3JyeSBtZSBpZiB0aGUga2VybmVsIGRlY2lkZWQgdG8gYXNzdW1lIGF0b21pYyBh bGlnbmVkCnNjYWxhciBhY2Nlc3NlcyBmb3IgYWxsIGFyY2hlcywgdGh1cyB0ZXJtaW5hdGluZyBz dXBwb3J0IGZvciBBbHBoYXMKd2l0aG91dCBCV1guCgpUaGUgWCBzZXJ2ZXIsIGV2ZXIgc2luY2Ug dGhlIGxpYnBjaWFjY2VzcyBjaGFuZ2UsIGRvZXMgbm90IHdvcmsgb24KQWxwaGFzIHdpdGhvdXQg QldYLgoKRGViaWFuIEFscGhhIChwcmV0dHkgbXVjaCB1cCB0byBkYXRlIGF0IERlYmlhbi1Qb3J0 cykgaXMgc3RpbGwgY29tcGlsZWQKZm9yIGFsbCBBbHBoYXMsIGkuZS4sIHdpdGhvdXQgQldYLiAg VGhlIGxhc3QgYXR0ZW1wdCB0byBzdGFydCBjb21waWxpbmcKRGViaWFuIEFscGhhIHdpdGggQldY LCBhYm91dCB0aHJlZSB5ZWFycyBhZ28gd2hlbiBBbHBoYSB3YXMga2lja2VkIG91dAp0byBEZWJp YW4tUG9ydHMgcmVzdWx0ZWQgaW4gYSBjb3VwbGUgb3Igc28gY29tcGxhaW50cyBzbyBnb3Qgbm93 aGVyZS4KSXQncyBmcnVzdHJhdGluZyBzdXBwb3J0aW5nIHRoZSBsb3dlc3QgY29tbW9uIGRlbW9u aW5hdG9yIGFzIG1hbnkgb2YKdGhlIGJ1Z3Mgc3BlY2lmaWMgdG8gQWxwaGEgY2FuIGJlIHJlc29s dmVkIGJ5IHJlY29tcGlsaW5nIHdpdGggdGhlIEJXWC4KVGhlIGtlcm5lbCBubyBsb25nZXIgc3Vw cG9ydGluZyBBbHBoYXMgd2l0aG91dCBCV1ggbWlnaHQganVzdCBiZSB0aGUKaW5jZW50aXZlIHdl IG5lZWQgdG8gc3dpdGNoIERlYmlhbiBBbHBoYSB0byBjb21waWxpbmcgd2l0aCBCV1guCgpDaGVl cnMKTWljaGFlbC4KX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19f X18KTGludXhwcGMtZGV2IG1haWxpbmcgbGlzdApMaW51eHBwYy1kZXZAbGlzdHMub3psYWJzLm9y ZwpodHRwczovL2xpc3RzLm96bGFicy5vcmcvbGlzdGluZm8vbGludXhwcGMtZGV2 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.orcon.net.nz ([219.88.242.59]:33363 "EHLO mail.orcon.net.nz" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1751828AbaIEIuN (ORCPT ); Fri, 5 Sep 2014 04:50:13 -0400 Date: Fri, 5 Sep 2014 20:16:48 +1200 From: Michael Cree Subject: Re: bit fields && data tearing Message-ID: <20140905081648.GB5281@omega> 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> <54091B30.2090509@zytor.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <54091B30.2090509@zytor.com> 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: <20140905081648.Dil2iCqSr78iKl9Tf1Fo2pCYGJU2Iz0OFNqhjWb34eA@z> On Thu, Sep 04, 2014 at 07:08:48PM -0700, H. Peter Anvin wrote: > On 09/04/2014 05:59 PM, Peter Hurley wrote: > > I have no idea how prevalent the ev56 is compared to the ev5. > > Still we're talking about a chip that came out in 1996. > > Ah yes, I stand corrected. According to Wikipedia, the affected CPUs > were all the 2106x CPUs (EV4, EV45, LCA4, LCA45) plus the 21164 with no > suffix (EV5). However, we're still talking about museum pieces here. Yes, that is correct, EV56 is the first Alpha CPU to have the byte-word extension (BWX) CPU instructions. It would not worry me if the kernel decided to assume atomic aligned scalar accesses for all arches, thus terminating support for Alphas without BWX. The X server, ever since the libpciaccess change, does not work on Alphas without BWX. Debian Alpha (pretty much up to date at Debian-Ports) is still compiled for all Alphas, i.e., without BWX. The last attempt to start compiling Debian Alpha with BWX, about three years ago when Alpha was kicked out to Debian-Ports resulted in a couple or so complaints so got nowhere. It's frustrating supporting the lowest common demoninator as many of the bugs specific to Alpha can be resolved by recompiling with the BWX. The kernel no longer supporting Alphas without BWX might just be the incentive we need to switch Debian Alpha to compiling with BWX. Cheers Michael.