From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262499AbTGaShd (ORCPT ); Thu, 31 Jul 2003 14:37:33 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262710AbTGaShd (ORCPT ); Thu, 31 Jul 2003 14:37:33 -0400 Received: from mail.jlokier.co.uk ([81.29.64.88]:42880 "EHLO mail.jlokier.co.uk") by vger.kernel.org with ESMTP id S262499AbTGaShc (ORCPT ); Thu, 31 Jul 2003 14:37:32 -0400 Date: Thu, 31 Jul 2003 19:37:30 +0100 From: Jamie Lokier To: Alan Cox Cc: Petr Vandrovec , lkml Subject: Re: TSCs are a no-no on i386 Message-ID: <20030731183730.GA7803@mail.jlokier.co.uk> References: <20030730135623.GA1873@lug-owl.de> <20030730181006.GB21734@fs.tum.de> <20030730183033.GA970@matchmail.com> <20030730184529.GE21734@fs.tum.de> <20030730202822.GG1873@lug-owl.de> <20030730215032.GA18892@vana.vc.cvut.cz> <1059606394.10505.24.camel@dhcp22.swansea.linux.org.uk> <20030731151020.GF6410@mail.jlokier.co.uk> <1059667304.16608.47.camel@dhcp22.swansea.linux.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1059667304.16608.47.camel@dhcp22.swansea.linux.org.uk> User-Agent: Mutt/1.4.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Alan Cox wrote: > > > And if the byte you are looking at was patched by another thread you've > > > blown it. Your emulation can only be so good 8) People do stuff like > > > patching instructions under software decode as a robustness check - its > > > normally pretty amusing > > > > On a uniprocessor 386, this is not a problem. Just disable preemption > > in the kernel decoder. > > Wrong again. Thats a common myth but you see I can put the instruction on a page > so that its executed from a page I just did a read() into in another process. If > I'm really bored I'll use O_DIRECT but thats mostly for makign life really bad > for non cache coherent setups 8) I wouldn't be surprised if even real CPUs mis-decode when there's a concurrent DMA into the area they are reading instructions from! :) -- Jamie