Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1765491AbZAOOSJ (ORCPT ); Thu, 15 Jan 2009 09:18:09 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1759477AbZAOOR4 (ORCPT ); Thu, 15 Jan 2009 09:17:56 -0500 Received: from mx3.mail.elte.hu ([157.181.1.138]:55978 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759430AbZAOORz (ORCPT ); Thu, 15 Jan 2009 09:17:55 -0500 Date: Thu, 15 Jan 2009 15:17:34 +0100 From: Ingo Molnar To: "Maciej W. Rozycki" Cc: Alan Cox , Jan-Benedict Glaw , Peter Zijlstra , Jiri Kosina , Adam Osuchowski , linux-kernel@vger.kernel.org, Nick Piggin , Thomas Gleixner , "H. Peter Anvin" Subject: Re: Is 386 processor still supported? Message-ID: <20090115141734.GA15732@elte.hu> References: <1231424025.11687.447.camel@twins> <1231424833.11687.452.camel@twins> <20090108150448.2393aeb0@lxorguk.ukuu.org.uk> <20090108151046.GK18120@elte.hu> <20090115123614.GR11087@lug-owl.de> <20090115133252.28c36adb@lxorguk.ukuu.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1313 Lines: 31 * Maciej W. Rozycki wrote: > On Thu, 15 Jan 2009, Alan Cox wrote: > > > > UP emulation of CMPXCHG and XADD for userland should be rather trivial, > > > so why not include it like with LL/SC for MIPS? > > > > Why not just ship an additional libc with the right options ? > > Does not work for MIPS as glibc has no equivalent code for pre-LL/SC > CPUs and LL/SC is always used. For the i386 the situation seems worse > yet as for pre-i486 CPUs a generic C implementation of > compare-and-exchange is used guaranteeing silent thread unsafety. :( > > IMO, a kernel emulation of CMPXCHG and XADD (both are used by > sysdeps/i386/i486/bits/atomic.h in glibc) with an optional LOCK prefix, > guaranteeing UP atomicity would be a cheap way to provide long-term i386 > userland support with little burden for both Linux and respective user > software maintainers. Certainly it adds some bloat to the kernel, but I > think it is not an option that should be outright dismissed without > consideration. patches are welcome ... Ingo -- 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/