From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757703AbZEVTxv (ORCPT ); Fri, 22 May 2009 15:53:51 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755165AbZEVTxn (ORCPT ); Fri, 22 May 2009 15:53:43 -0400 Received: from mx-out2.daemonmail.net ([216.104.160.39]:49958 "EHLO mx-out2.daemonmail.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751688AbZEVTxm (ORCPT ); Fri, 22 May 2009 15:53:42 -0400 From: "Michael S. Zick" Reply-To: lkml@morethan.org To: Andi Kleen Subject: Re: [BUG FIX] Make x86_32 uni-processor Atomic ops, Atomic Date: Fri, 22 May 2009 14:53:39 -0500 User-Agent: KMail/1.9.9 Cc: linux-kernel@vger.kernel.org References: <200905221139.26941.lkml@morethan.org> <200905221343.30638.lkml@morethan.org> <20090522192329.GF846@one.firstfloor.org> In-Reply-To: <20090522192329.GF846@one.firstfloor.org> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200905221453.41895.lkml@morethan.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri May 22 2009, Andi Kleen wrote: > On Fri, May 22, 2009 at 01:43:27PM -0500, Michael S. Zick wrote: > > On Fri May 22 2009, you wrote: > > > "Michael S. Zick" writes: > > > > > > > Found in the bit-rot for 32-bit, x86, Uni-processor builds: > > > > > > Actually uni processor should not use the lock prefix > > > because it doesn't need it; the only exception are some special > > > ops used in para-virtualization which are special cased. > > > > > > > Unless you have interrupts enabled, then you have two contexts. > > Interrupts on the local CPU don't interrupt instructions, only > inbetween. > Ref: http://developer.intel.com/Assets/PDF/manual/253666.pdf Manual page: 3-590 PDF page: 638 Summary: Processors prior to P-4 can take an interrupt between the read cycle and the write cycle. Which is why opcode 0xF0 exists. Mike > -Andi