Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1765422AbZAOOU7 (ORCPT ); Thu, 15 Jan 2009 09:20:59 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755987AbZAOOUu (ORCPT ); Thu, 15 Jan 2009 09:20:50 -0500 Received: from lug-owl.de ([195.71.106.12]:58406 "EHLO lug-owl.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755174AbZAOOUt (ORCPT ); Thu, 15 Jan 2009 09:20:49 -0500 Date: Thu, 15 Jan 2009 15:20:47 +0100 From: Jan-Benedict Glaw To: "Maciej W. Rozycki" Cc: 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? Message-ID: <20090115142047.GV11087@lug-owl.de> Mail-Followup-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" 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: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="KMT2bFHAEoOkugdu" Content-Disposition: inline In-Reply-To: X-Operating-System: Linux mail 2.6.18-5-686 X-gpg-fingerprint: 250D 3BCF 7127 0D8C A444 A961 1DBD 5E75 8399 E1BB X-gpg-key: wwwkeys.de.pgp.net X-Echelon-Enable: howto poison arsenous mail psychological biological nuclear warfare test the bombastical terror of flooding the spy listeners explosion sex drugs and rock'n'roll X-TKUeV: howto poison arsenous mail psychological biological nuclear warfare test the bombastical terror of flooding the spy listeners explosion sex drugs and rock'n'roll X-message-flag: Please send plain text messages only. Do not send HTML emails. Thank you. User-Agent: Mutt/1.5.13 (2006-08-11) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2811 Lines: 76 --KMT2bFHAEoOkugdu Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable 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 trivi= al,=20 > > > so why not include it like with LL/SC for MIPS? > >=20 > > Why not just ship an additional libc with the right options ? >=20 > Does not work for MIPS as glibc has no equivalent code for pre-LL/SC CPU= s=20 > and LL/SC is always used. For the i386 the situation seems worse yet as= =20 > for pre-i486 CPUs a generic C implementation of compare-and-exchange is= =20 > used guaranteeing silent thread unsafety. :( >=20 > IMO, a kernel emulation of CMPXCHG and XADD (both are used by=20 > sysdeps/i386/i486/bits/atomic.h in glibc) with an optional LOCK prefix,= =20 > guaranteeing UP atomicity would be a cheap way to provide long-term i386= =20 > userland support with little burden for both Linux and respective user=20 > software maintainers. Certainly it adds some bloat to the kernel, but I= =20 > think it is not an option that should be outright dismissed without=20 > 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?) 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 --=20 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 Bet= t, wie fr=C3=BCher meine Kinder?) 00:00 <@jbglaw> jever2: *patsch* 00:01 <@jever2> *aua*, wof=C3=BCr, 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! --KMT2bFHAEoOkugdu Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.6 (GNU/Linux) iD8DBQFJb0Y/Hb1edYOZ4bsRAnEeAJ9JkaqmDFOGp1uPNzBe4qeSgl19dQCeI123 c4oTq/pPCaUPcdJp3a/GsbU= =wHyn -----END PGP SIGNATURE----- --KMT2bFHAEoOkugdu-- -- 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/