From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759153AbYEOLR4 (ORCPT ); Thu, 15 May 2008 07:17:56 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753081AbYEOLRs (ORCPT ); Thu, 15 May 2008 07:17:48 -0400 Received: from ozlabs.org ([203.10.76.45]:58803 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752947AbYEOLRs (ORCPT ); Thu, 15 May 2008 07:17:48 -0400 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-ID: <18476.5290.709729.582063@cargo.ozlabs.ibm.com> Date: Thu, 15 May 2008 20:47:06 +1000 From: Paul Mackerras To: Carl Love Cc: linuxppc-dev , linux-kernel , Maynard Johnson Subject: Re: [PATCH] Fix for OProfile callgraph for Power 64 bit user apps In-Reply-To: <1210183924.7726.28.camel@carll-linux-desktop> References: <1210183924.7726.28.camel@carll-linux-desktop> X-Mailer: VM 7.19 under Emacs 22.1.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Carl Love writes: > The following patch fixes the 64 bit user code backtrace > which currently may hang the system. What exactly is wrong with it? Having now taken a much closer look, I now don't think Nate Case's patch addresses this, since it only affects constant size arguments <= 8 to copy_{to,from}_user_inatomic. However, I don't see why your patch fixes anything. It means we do two access_ok calls and two __copy_from_user_inatomic calls, for 8 bytes, at sp and at sp + 16, rather than doing one access_ok and __copy_from_user_inatomic for 24 bytes at sp. Why does that make any difference (apart from being slower)? Paul.