From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tim Deegan Subject: Re: [PATCH] libvchan: interdomain communications library Date: Thu, 25 Aug 2011 11:27:38 +0100 Message-ID: <20110825102738.GA79827@ocelot.phlegethon.org> References: <1313764724-12683-1-git-send-email-dgdegra@tycho.nsa.gov> <1314004557.5010.411.camel@zakaz.uk.xensource.com> <4E554884.1040109@tycho.nsa.gov> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Return-path: Content-Disposition: inline In-Reply-To: <4E554884.1040109@tycho.nsa.gov> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Daniel De Graaf Cc: "xen-devel@lists.xensource.com" , Ian Campbell , "konrad.wilk@oracle.com" , Stefano Stabellini List-Id: xen-devel@lists.xenproject.org At 14:52 -0400 on 24 Aug (1314197572), Daniel De Graaf wrote: > Agreed, barriers are needed for a robust implementation. Since this is > a shared library and not xen or kernel code, the existing barrier()/wmb() > functions are not available. The only existing implementations in Xen > appear to expand to asm("":::"memory") which does not actually implement > a memory barrier (i.e. MFENCE or similar opcodes). AIUI on x86_64, writes are guaranteed to be seen in order so the only thing that barrier has to protect against is the compiler reordering the writes. Tim. -- Tim Deegan Principal Software Engineer, Xen Platform Team Citrix Systems UK Ltd. (Company #02937203, SL9 0BG)