From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750835Ab3AGFbj (ORCPT ); Mon, 7 Jan 2013 00:31:39 -0500 Received: from fgwmail5.fujitsu.co.jp ([192.51.44.35]:56859 "EHLO fgwmail5.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750776Ab3AGFbd (ORCPT ); Mon, 7 Jan 2013 00:31:33 -0500 X-SecurityPolicyCheck: OK by SHieldMailChecker v1.8.4 Message-ID: <50EA5D7D.7000703@jp.fujitsu.com> Date: Mon, 07 Jan 2013 14:30:37 +0900 From: Kamezawa Hiroyuki User-Agent: Mozilla/5.0 (Windows NT 6.1; rv:17.0) Gecko/17.0 Thunderbird/17.0 MIME-Version: 1.0 To: Wen Congyang CC: Tang Chen , akpm@linux-foundation.org, rientjes@google.com, liuj97@gmail.com, len.brown@intel.com, benh@kernel.crashing.org, paulus@samba.org, cl@linux.com, minchan.kim@gmail.com, kosaki.motohiro@jp.fujitsu.com, isimatu.yasuaki@jp.fujitsu.com, wujianguo@huawei.com, hpa@zytor.com, linfeng@cn.fujitsu.com, laijs@cn.fujitsu.com, mgorman@suse.de, yinghai@kernel.org, x86@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-acpi@vger.kernel.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, linux-ia64@vger.kernel.org, cmetcalf@tilera.com, sparclinux@vger.kernel.org Subject: Re: [PATCH v5 14/14] memory-hotplug: free node_data when a node is offlined References: <1356350964-13437-1-git-send-email-tangchen@cn.fujitsu.com> <1356350964-13437-15-git-send-email-tangchen@cn.fujitsu.com> <50DA7533.6060407@jp.fujitsu.com> <50DC3C26.6060308@cn.fujitsu.com> <50DCE7C0.8070407@jp.fujitsu.com> <50DFD8F4.7040301@cn.fujitsu.com> In-Reply-To: <50DFD8F4.7040301@cn.fujitsu.com> Content-Type: text/plain; charset=ISO-2022-JP Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org (2012/12/30 15:02), Wen Congyang wrote: > At 12/28/2012 08:28 AM, Kamezawa Hiroyuki Wrote: >> (2012/12/27 21:16), Wen Congyang wrote: >>> At 12/26/2012 11:55 AM, Kamezawa Hiroyuki Wrote: >>>> (2012/12/24 21:09), Tang Chen wrote: >>>>> From: Wen Congyang >>>>> >>>>> We call hotadd_new_pgdat() to allocate memory to store node_data. So we >>>>> should free it when removing a node. >>>>> >>>>> Signed-off-by: Wen Congyang >>>> >>>> I'm sorry but is it safe to remove pgdat ? All zone cache and zonelists are >>>> properly cleared/rebuilded in synchronous way ? and No threads are visinting >>>> zone in vmscan.c ? >>> >>> We have rebuilt zonelists when a zone has no memory after offlining some pages. >>> >> >> How do you guarantee that the address of pgdat/zone is not on stack of any kernel >> threads or other kernel objects without reference counting or other syncing method ? > > No way to guarentee this. But, the kernel should not use the address of pgdat/zone when > it is offlined. > > Hmm, what about this: reuse the memory when the node is onlined again? > That's the only way which we can go now. Please don't free it. Thanks, -Kame