Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1765840AbZAOOhe (ORCPT ); Thu, 15 Jan 2009 09:37:34 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758563AbZAOOhR (ORCPT ); Thu, 15 Jan 2009 09:37:17 -0500 Received: from fg-out-1718.google.com ([72.14.220.154]:34681 "EHLO fg-out-1718.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757314AbZAOOhP convert rfc822-to-8bit (ORCPT ); Thu, 15 Jan 2009 09:37:15 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:to:subject:in-reply-to:mime-version :content-type:content-transfer-encoding:content-disposition :references; b=dTuXxI1TZZNoZNgrP91eCGm53hEn/sjKA4/6nv4Y/rl7WnE51ICYxU4FFeURnvSwco XiBchHk7XiM72nos7iP2xgpml+uk1f1a6FTI7siW/X8hitETjBit2lOOpkoBNxJ7dddP af5aMHZm8/WH7h4JV4P/6eqUaEmnFGKba/TkI= Message-ID: <195c7a900901150637r4a8d374dhe00ac47592c9c0d3@mail.gmail.com> Date: Thu, 15 Jan 2009 15:37:12 +0100 From: "Bastien ROUCARIES" To: "Maciej W. Rozycki" , "Alan Cox" , "Ingo Molnar" , "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? In-Reply-To: <20090115142047.GV11087@lug-owl.de> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Content-Disposition: inline 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> <20090115142047.GV11087@lug-owl.de> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2690 Lines: 61 On Thu, Jan 15, 2009 at 3:20 PM, Jan-Benedict Glaw wrote: > On Thu, 2009-01-15 14:15:56 +0000, 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. > > I just searched for the old patch, but couldn't find it ad hoc. (But > it must be somewhere, at least in the archives, I guess?) here http://thread.gmane.org/gmane.linux.kernel/205839, but should be securized (use get_user() ) Regards > The kernel emulator has the benefit of no overhead when not switched > on, and low-to-no overhead when not being used (i386 capable kernel on > i486 hardware). > > Heck, I'd dig out my two test systems and give them a try with current > Debian unstable. Should be fun with four to eight megabytes of RAM. > > MfG, JBG > > -- > Jan-Benedict Glaw jbglaw@lug-owl.de +49-172-7608481 > Signature of: 23:53 <@jbglaw> So, ich kletter' jetzt mal ins Bett. > the second : 23:57 <@jever2> .oO( kletter ..., hat er noch Gitter vorm Bett, wie fr?her meine Kinder?) > 00:00 <@jbglaw> jever2: *patsch* > 00:01 <@jever2> *aua*, wof?r, Gedanken sind frei! > 00:02 <@jbglaw> Nee, freie Gedanken, die sind seit 1984 doch aus! > 00:03 <@jever2> 1984? ich bin erst seit 1985 verheiratet! > > -----BEGIN PGP SIGNATURE----- > Version: GnuPG v1.4.6 (GNU/Linux) > > iD8DBQFJb0Y/Hb1edYOZ4bsRAnEeAJ9JkaqmDFOGp1uPNzBe4qeSgl19dQCeI123 > c4oTq/pPCaUPcdJp3a/GsbU= > =wHyn > -----END PGP SIGNATURE----- > > -- 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/