Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752296Ab3IJWDC (ORCPT ); Tue, 10 Sep 2013 18:03:02 -0400 Received: from mail-vc0-f182.google.com ([209.85.220.182]:60901 "EHLO mail-vc0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751424Ab3IJWC7 (ORCPT ); Tue, 10 Sep 2013 18:02:59 -0400 MIME-Version: 1.0 In-Reply-To: <522F9464.9070806@zytor.com> References: <20130910130811.507933095@infradead.org> <20130910135152.GD7537@gmail.com> <20130910135636.GA8268@gmail.com> <20130910164519.GL31370@twins.programming.kicks-ass.net> <20130910212509.GA18147@laptop.programming.kicks-ass.net> <522F9464.9070806@zytor.com> Date: Tue, 10 Sep 2013 15:02:58 -0700 X-Google-Sender-Auth: hmgi5lMgK1a5ukENseiAVLNtDCY Message-ID: Subject: Re: [PATCH 0/7] preempt_count rework -v2 From: Linus Torvalds To: "H. Peter Anvin" Cc: Peter Zijlstra , Ingo Molnar , Andi Kleen , Mike Galbraith , Thomas Gleixner , Arjan van de Ven , Frederic Weisbecker , Linux Kernel Mailing List , "linux-arch@vger.kernel.org" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1281 Lines: 35 On Tue, Sep 10, 2013 at 2:51 PM, H. Peter Anvin wrote: > On 09/10/2013 02:43 PM, Linus Torvalds wrote: > > Actually, the right thing here really is "er" (which I think you meant, > but just to make it clear.) Yes, I was just answering the i-vs-e confusion. > "e" doesn't work on versions of gcc older than the first x86-64 release, > but we don't care about that anymore. Indeed. > A final good question is if we should encapsulate the add/inc and > sub/dec into a single function; one could easily do somethin glike: Yes. However, I would do that at a higher level than the one that builds the actual functions. That said, there's a few cases where you might want to specify add-vs-sub explicitly, but they are rather odd, namely the fact that "-128" fits in a byte, but "128" does not. So it can be better to add 128 by doing a "subl $-128" than by doing an "add $128". But we probably don't have any situation where we care about that special value of "128". I've seen the trick, though. Linus -- 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/