From owner-svn-src-head@FreeBSD.ORG Mon Jun 4 12:51:04 2012 Return-Path: Delivered-To: svn-src-head@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52]) by hub.freebsd.org (Postfix) with ESMTP id B6F0E106564A; Mon, 4 Jun 2012 12:51:04 +0000 (UTC) (envelope-from kostikbel@gmail.com) Received: from mail.zoral.com.ua (mx0.zoral.com.ua [91.193.166.200]) by mx1.freebsd.org (Postfix) with ESMTP id 1547D8FC26; Mon, 4 Jun 2012 12:51:03 +0000 (UTC) Received: from skuns.kiev.zoral.com.ua (localhost [127.0.0.1]) by mail.zoral.com.ua (8.14.2/8.14.2) with ESMTP id q54CooJ8097542; Mon, 4 Jun 2012 15:50:50 +0300 (EEST) (envelope-from kostikbel@gmail.com) Received: from deviant.kiev.zoral.com.ua (kostik@localhost [127.0.0.1]) by deviant.kiev.zoral.com.ua (8.14.5/8.14.5) with ESMTP id q54CooLc091323; Mon, 4 Jun 2012 15:50:50 +0300 (EEST) (envelope-from kostikbel@gmail.com) Received: (from kostik@localhost) by deviant.kiev.zoral.com.ua (8.14.5/8.14.5/Submit) id q54Coo08091322; Mon, 4 Jun 2012 15:50:50 +0300 (EEST) (envelope-from kostikbel@gmail.com) X-Authentication-Warning: deviant.kiev.zoral.com.ua: kostik set sender to kostikbel@gmail.com using -f Date: Mon, 4 Jun 2012 15:50:50 +0300 From: Konstantin Belousov To: Tijl Coosemans Message-ID: <20120604125050.GA85127@deviant.kiev.zoral.com.ua> References: <201206021810.q52IAGZA004238@svn.freebsd.org> <4FCC873B.90104@freebsd.org> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="5vNYLRcllDrimb99" Content-Disposition: inline In-Reply-To: <4FCC873B.90104@freebsd.org> User-Agent: Mutt/1.4.2.3i X-Virus-Scanned: clamav-milter 0.95.2 at skuns.kiev.zoral.com.ua X-Virus-Status: Clean X-Spam-Status: No, score=-4.0 required=5.0 tests=ALL_TRUSTED,AWL,BAYES_00 autolearn=ham version=3.2.5 X-Spam-Checker-Version: SpamAssassin 3.2.5 (2008-06-10) on skuns.kiev.zoral.com.ua Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org Subject: Re: svn commit: r236456 - in head/sys: amd64/include i386/include X-BeenThere: svn-src-head@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: SVN commit messages for the src tree for head/-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 04 Jun 2012 12:51:04 -0000 --5vNYLRcllDrimb99 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Jun 04, 2012 at 12:00:27PM +0200, Tijl Coosemans wrote: > On 02-06-2012 20:10, Konstantin Belousov wrote: > > Author: kib > > Date: Sat Jun 2 18:10:16 2012 > > New Revision: 236456 > > URL: http://svn.freebsd.org/changeset/base/236456 > >=20 > > Log: > > Use plain store for atomic_store_rel on x86, instead of implicitly > > locked xchg instruction. IA32 memory model guarantees that store has > > release semantic, since stores cannot pass loads or stores. >=20 > They can pass non-temporal stores can't they? Sure. But (our) barriers only work for WB memory accesses, in respect to ot= her WB memory accesses. The atomic(9) contains not quite explicit mention of the requirement, for ia32 and more direct notion for ia64. It could probably be reworded to mention memory access type explicitely for ia32 too. At least the code which I saw and maintain which uses the mixed accesses to the same physical page, sometime including non-CPU caches coherency protocols, use explicit {s,m}fence barriers as needed. --5vNYLRcllDrimb99 Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (FreeBSD) iEYEARECAAYFAk/MrykACgkQC3+MBN1Mb4gfcwCfZegTw+qe1tj4qPpT8osb1267 SpgAnivKjpW3WAIf7FOx7DrJtkAcloaL =QyCF -----END PGP SIGNATURE----- --5vNYLRcllDrimb99--