Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759215AbYGRWnl (ORCPT ); Fri, 18 Jul 2008 18:43:41 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756457AbYGRWn3 (ORCPT ); Fri, 18 Jul 2008 18:43:29 -0400 Received: from smtp-outbound-1.vmware.com ([65.113.40.141]:34415 "EHLO smtp-outbound-1.vmware.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753909AbYGRWn3 (ORCPT ); Fri, 18 Jul 2008 18:43:29 -0400 Subject: Re: [PATCH] x86: APIC: Remove apic_write_around(); use alternatives From: Zachary Amsden To: "Maciej W. Rozycki" Cc: Yinghai Lu , Ingo Molnar , "x86@kernel.org" , "linux-kernel@vger.kernel.org" , Suresh Siddha , Jeremy Fitzhardinge In-Reply-To: References: <20080718105259.GY6875@elte.hu> <86802c440807180925t6fadfa58r6bf7740f8145482e@mail.gmail.com> <86802c440807181001h4426c197vc474f81497a5b42@mail.gmail.com> <20080718210348.GB24373@elte.hu> <86802c440807181413n7e79e821l90afaae86b322de9@mail.gmail.com> Content-Type: text/plain Date: Fri, 18 Jul 2008 15:42:17 -0700 Message-Id: <1216420937.30348.30.camel@bodhitayantram.eng.vmware.com> Mime-Version: 1.0 X-Mailer: Evolution 2.22.2 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2147 Lines: 47 On Fri, 2008-07-18 at 15:02 -0700, Maciej W. Rozycki wrote: > On Fri, 18 Jul 2008, Yinghai Lu wrote: > > > CC arch/x86/kernel/apic_64.o > > arch/x86/kernel/apic_64.c:170: error: unknown field 'write_atomic' > > specified in initializer > > arch/x86/kernel/apic_64.c:170: error: 'native_apic_mem_write_atomic' > > undeclared here (not in a function) > > arch/x86/kernel/apic_64.c:209: error: unknown field 'write_atomic' > > specified in initializer > > arch/x86/kernel/apic_64.c:209: warning: initialization from > > incompatible pointer type > > make[1]: *** [arch/x86/kernel/apic_64.o] Error 1 > > make: *** [arch/x86/kernel] Error 2 > > Just remove the offending initialisers. They are not needed anymore as > the .write method is now used universally including places where > .write_atomic was. I just could not stand watching the thing > proliferate... Thank you for cleaning this up Yinghai, but this really begs the question - is having write_atomic REALLY worthwhile? Intel themselves have not supported the affected processors since October 17, 2000, and here we are writing code for it, when the last processor with such a flaw (C2 or cB1 stepping Pentium) was stamped in 1995, over 13 years ago. It might have been relevant when Linus was developing SMP support in '96, but it isn't now. In fact, anyone running a 120 Mhz or 133 Mhz Pentium processor that has been obsoleted for 8 years should at this point be shot for wasting energy with their poor megawatt/megaflop ratio, doubly so if they can claim to be doing so in some kind of SMP scenario which even requires using an APIC at all. Seriously, please consider removing all of the flaming crap surrounding apic_write_around entirely and forcing users who compile for less than 686 processors to just not have official support for local APIC at all, or just default it off and let people turn it on at own risk. Zach -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/