From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753587AbaD3E0m (ORCPT ); Wed, 30 Apr 2014 00:26:42 -0400 Received: from mga09.intel.com ([134.134.136.24]:37041 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750978AbaD3E0k (ORCPT ); Wed, 30 Apr 2014 00:26:40 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.97,956,1389772800"; d="scan'208";a="532185376" Message-ID: <53607B7D.6050205@linux.intel.com> Date: Wed, 30 Apr 2014 12:26:37 +0800 From: Jiang Liu Organization: Intel User-Agent: Mozilla/5.0 (Windows NT 6.2; WOW64; rv:24.0) Gecko/20100101 Thunderbird/24.4.0 MIME-Version: 1.0 To: Peter Zijlstra CC: Andrew Morton , Ingo Molnar , David Rientjes , Ingo Molnar , "Rafael J . Wysocki" , Tony Luck , linux-kernel@vger.kernel.org Subject: Re: [Bugfix v2] sched: fix possible invalid memory access caused by CPU hot-addition References: <1398653293-12483-1-git-send-email-jiang.liu@linux.intel.com> <20140428070954.GM11096@twins.programming.kicks-ass.net> In-Reply-To: <20140428070954.GM11096@twins.programming.kicks-ass.net> 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 Thanks Peter, I will try to find other solutions. On 2014/4/28 15:09, Peter Zijlstra wrote: > On Mon, Apr 28, 2014 at 10:48:13AM +0800, Jiang Liu wrote: >> Intel platforms with Nehalem/Westmere/IvyBridge CPUs may support socket >> hotplug/online at runtime. The CPU hot-addition flow is: >> 1) handle CPU hot-addition event >> 1.a) gather platform specific information >> 1.b) associate hot-added CPU with NUMA node >> 1.c) create CPU device >> 2) online hot-added CPU through sysfs: >> 2.a) cpu_up() >> 2.b) ->try_online_node() >> 2.c) ->hotadd_new_pgdat() >> 2.d) ->node_set_online() >> >> Between 1.b and 2.c, hot-added CPUs are associated with NUMA nodes >> but those NUMA nodes may still be in offlined state. So we should >> check node_online(nid) before calling kmalloc_node(nid) and friends, >> otherwise it may cause invalid memory access as below. > > So complete and full NAK on this. This is a workaround for a fucked in > the head BIOS. If you're going to do a work around for that they should > live in arch/ space, not in core code. > > The code in question is nearly 7 years old (2.6.24), which leads me to > believe it works just fine for (regular) memory less nodes as I've not > had complaints about it before. > -- > 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/ >