Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758545Ab1FVTkU (ORCPT ); Wed, 22 Jun 2011 15:40:20 -0400 Received: from claw.goop.org ([74.207.240.146]:57826 "EHLO claw.goop.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758080Ab1FVTkT (ORCPT ); Wed, 22 Jun 2011 15:40:19 -0400 Message-ID: <4E0240AC.9060603@goop.org> Date: Wed, 22 Jun 2011 12:21:16 -0700 From: Jeremy Fitzhardinge User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.17) Gecko/20110428 Fedora/3.1.10-1.fc15 Lightning/1.0b3pre Thunderbird/3.1.10 MIME-Version: 1.0 To: Peter Zijlstra CC: "H. Peter Anvin" , Ingo Molnar , the arch/x86 maintainers , Linux Kernel Mailing List , Nick Piggin , Jeremy Fitzhardinge , Linus Torvalds Subject: Re: [PATCH RFC 0/7] x86: convert ticketlocks to C and remove duplicate code References: <1308664868.26237.173.camel@twins> In-Reply-To: <1308664868.26237.173.camel@twins> X-Enigmail-Version: 1.1.2 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1161 Lines: 33 On 06/21/2011 07:01 AM, Peter Zijlstra wrote: > One other thing you could contemplate is adding something like: > > #define xadd(ptr, inc) \ > do { \ > switch(sizeof(*(ptr))) { \ > case 1: \ > asm volatile (LOCK_PREFIX "xaddb %0, %1\n" \ > : "+r" (inc), "+m" (*(ptr)) \ > : : "memory", "cc"); \ > case 2: > ... xaddw ... > case 4: > ... xaddl ... > } while (0) > > and a similar something for inc. For both there seem to be various asm > bits left (we could even consider adding xadd to > arch/x86/include/asm/cmpxchg*.h). A friend just pointed out that gcc has a "__sync_fetch_and_add()" intrinsic, which compiles to xadd when used in this context. What's the general feeling about using these kinds of gcc features? It also has __sync_bool_compare_and_swap(), which would simplify a lot of asm/cmpxchg.h... J -- 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/