Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S966643Ab3DQOSu (ORCPT ); Wed, 17 Apr 2013 10:18:50 -0400 Received: from mga03.intel.com ([143.182.124.21]:49716 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S966409Ab3DQOSt (ORCPT ); Wed, 17 Apr 2013 10:18:49 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.87,492,1363158000"; d="scan'208";a="287444595" Message-ID: <516EAF31.8000107@linux.intel.com> Date: Wed, 17 Apr 2013 07:18:25 -0700 From: Darren Hart User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130110 Thunderbird/17.0.2 MIME-Version: 1.0 To: zhang.yi20@zte.com.cn CC: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Ingo Molnar , Peter Zijlstra , Thomas Gleixner , Dave Hansen Subject: Re: [PATCH] futex: bugfix for futex-key conflict when futex use hugepage References: In-Reply-To: X-Enigmail-Version: 1.5.1 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1339 Lines: 38 On 04/17/2013 02:55 AM, zhang.yi20@zte.com.cn wrote: > Darren Hart wrote on 2013/04/17 01:57:10: > >> Again, a functional testcase in futextest would be a good idea. This >> helps validate the patch and also can be used to identify regressions in >> the future. > > I will post the testcase code later. > >> >> What is the max value of comp_idx? Are we at risk of truncating it? >> Looks like not really from my initial look. >> >> This also needs a comment in futex.h describing the usage of the offset >> field in union futex_key as well as above get_futex_key describing the >> key for shared mappings. >> >> > > As far as I know , the max size of one hugepage is 1 GBytes for x86 cpu. > Can some other cpus support greater hugepage even more than 4 GBytes? If > so, we can change the type of 'offset' from int to long to avoid > truncating. I discussed this with Dave Hansen, on CC, and he thought we needed 9 bits, so even on x86 32b we should be covered. -- Darren Hart Intel Open Source Technology Center Yocto Project - Technical Lead - Linux Kernel -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/