From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wen Congyang Date: Sat, 20 Oct 2012 00:50:45 +0000 Subject: Re: [PATCH 1/10] memory-hotplug : check whether memory is offline or not when removing memory Message-Id: <5081F565.8020605@cn.fujitsu.com> List-Id: References: <506E43E0.70507@jp.fujitsu.com> <506E451E.1050403@jp.fujitsu.com> <50812F13.20503@cn.fujitsu.com> <5081609C.9080702@gmail.com> In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: KOSAKI Motohiro Cc: Wen Congyang , Yasuaki Ishimatsu , 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, rientjes@google.com, liuj97@gmail.com, len.brown@intel.com, cl@linux.com, minchan.kim@gmail.com, akpm@linux-foundation.org At 10/20/2012 02:33 AM, KOSAKI Motohiro Wrote: >> I think it again, and found that this check is necessary. Because we only >> lock memory hotplug when offlining pages. Here is the steps to offline and >> remove memory: >> >> 1. lock memory hotplug >> 2. offline a memory section >> 3. unlock memory hotplug >> 4. repeat 1-3 to offline all memory sections >> 5. lock memory hotplug >> 6. remove memory >> 7. unlock memory hotplug >> >> All memory sections must be offlined before removing memory. But we don't >> hold >> the lock in the whole operation. So we should check whether all memory >> sections >> are offlined before step6. > > You should describe the race scenario in the patch description. OK? > OK Thanks Wen Congyang