Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030502Ab3HIHaN (ORCPT ); Fri, 9 Aug 2013 03:30:13 -0400 Received: from cn.fujitsu.com ([222.73.24.84]:9175 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1030401Ab3HIHaL (ORCPT ); Fri, 9 Aug 2013 03:30:11 -0400 X-IronPort-AV: E=Sophos;i="4.89,844,1367942400"; d="scan'208";a="8161678" Message-ID: <52049A2E.8080101@cn.fujitsu.com> Date: Fri, 09 Aug 2013 15:28:46 +0800 From: Tang Chen User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:12.0) Gecko/20120430 Thunderbird/12.0.1 MIME-Version: 1.0 To: Toshi Kani CC: Yasuaki Ishimatsu , rafael.j.wysocki@intel.com, linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org, Wen Congyang Subject: Re: [PATCH] ACPI, cpu hotplug: move try_offline_node() after acpi_unmap_lsapic() References: <5200CBBF.1090904@jp.fujitsu.com> <1375808178.10300.181.camel@misato.fc.hp.com> In-Reply-To: <1375808178.10300.181.camel@misato.fc.hp.com> X-MIMETrack: Itemize by SMTP Server on mailserver/fnst(Release 8.5.3|September 15, 2011) at 2013/08/09 15:28:42, Serialize by Router on mailserver/fnst(Release 8.5.3|September 15, 2011) at 2013/08/09 15:28:43, Serialize complete at 2013/08/09 15:28:43 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=UTF-8; format=flowed Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1864 Lines: 46 On 08/07/2013 12:56 AM, Toshi Kani wrote: > On Tue, 2013-08-06 at 19:11 +0900, Yasuaki Ishimatsu wrote: >> try_offline_node() checks that all cpus related with removed node have been >> removed by using cpu_present_bits. If all cpus related with removed node have >> been removed, try_offline_node() clears the node information. >> >> But try_offline_node() called from acpi_processor_remove() never clears >> the node information. For disabling cpu_present_bits, acpi_unmap_lsapic() >> need be called. But acpi_unmap_lsapic() is called after try_offline_node() >> runs. So when try_offline_node() runs, the cpu's cpu_present_bits is always >> set. >> >> This patch moves try_offline_node() after acpi_unmap_lsapic(). >> >> Signed-off-by: Yasuaki Ishimatsu > > The change looks good to me. > > Acked-by: Toshi Kani > > BTW, do you know why try_offline_node() has to use stop_machine()? try_offline_node() is used to check if the node could be hot-removed after each memory or cpu hot-remove operation. In memory hot-remove path, we have lock_memory_hotplug() to series all the memory hot-remove options. But when doing cpu hot-remove, acpi_processor_remove() |->try_offline_node() There is no lock to protect it. I think, when we are going to hot-remove a node, others should not do any memory or cpu hotplug operation. In memory hotplug path, we have lock_memory_hotplug(). But in cpu hotplug path, I didn't find any lock. So we used stop_machine() to call check_cpu_on_node(). If we find any cpu still present, we return and do not remove the node. Thanks. -- 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/