From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-oi0-f46.google.com (mail-oi0-f46.google.com [209.85.218.46]) by kanga.kvack.org (Postfix) with ESMTP id 92AFA90002E for ; Tue, 10 Mar 2015 22:53:58 -0400 (EDT) Received: by oifu20 with SMTP id u20so5375336oif.11 for ; Tue, 10 Mar 2015 19:53:58 -0700 (PDT) Received: from szxga03-in.huawei.com (szxga03-in.huawei.com. [119.145.14.66]) by mx.google.com with ESMTPS id m6si979832oel.34.2015.03.10.19.53.55 for (version=TLSv1 cipher=RC4-SHA bits=128/128); Tue, 10 Mar 2015 19:53:57 -0700 (PDT) Message-ID: <54FFADB6.60604@huawei.com> Date: Wed, 11 Mar 2015 10:51:34 +0800 From: Xie XiuQi MIME-Version: 1.0 Subject: Re: node-hotplug: is memset 0 safe in try_offline_node()? References: <54F52ACF.4030103@huawei.com> <54F81322.8010202@cn.fujitsu.com> <54F8243D.7020809@huawei.com> <54FF9662.8080303@cn.fujitsu.com> In-Reply-To: <54FF9662.8080303@cn.fujitsu.com> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Gu Zheng , Xishi Qiu Cc: Yasuaki Ishimatsu , Andrew Morton , Tang Chen , Yinghai Lu , Linux MM , LKML , Toshi Kani , Mel Gorman , Tejun Heo , Kamezawa Hiroyuki On 2015/3/11 9:12, Gu Zheng wrote: > Hi Xishi, > > What is the condition of this problem now? Hi Gu, I have no machine to do this test now. But I've tested the patch "just remove memset 0" more than 20 hours last week, it's OK. Thanks, Xie XiuQi > > Regards, > Gu > On 03/05/2015 05:39 PM, Xishi Qiu wrote: > >> On 2015/3/5 16:26, Gu Zheng wrote: >> >>> Hi Xishi, >>> Could you please try the following one? >>> It postpones the reset of obsolete pgdat from try_offline_node() to >>> hotadd_new_pgdat(), and just resetting pgdat->nr_zones and >>> pgdat->classzone_idx to be 0 rather than the whole reset by memset() >>> as Kame suggested. >>> >>> Regards, >>> Gu >>> >>> --- >>> mm/memory_hotplug.c | 13 ++++--------- >>> 1 files changed, 4 insertions(+), 9 deletions(-) >>> >>> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c >>> index 1778628..c17eebf 100644 >>> --- a/mm/memory_hotplug.c >>> +++ b/mm/memory_hotplug.c >>> @@ -1092,6 +1092,10 @@ static pg_data_t __ref *hotadd_new_pgdat(int nid, u64 start) >>> return NULL; >>> >>> arch_refresh_nodedata(nid, pgdat); >>> + } else { >>> + /* Reset the nr_zones and classzone_idx to 0 before reuse */ >>> + pgdat->nr_zones = 0; >>> + pgdat->classzone_idx = 0; >> >> Hi Gu, >> >> This is just to avoid the warning, I think it's no meaning. >> Here is the changlog from the original patch: >> >> commit 88fdf75d1bb51d85ba00c466391770056d44bc03 >> ... >> Warn if memory-hotplug/boot code doesn't initialize pg_data_t with zero >> when it is allocated. Arch code and memory hotplug already initiailize >> pg_data_t. So this warning should never happen. I select fields *randomly* >> near the beginning, middle and end of pg_data_t for checking. >> ... >> >> Thanks, >> Xishi Qiu >> >>> } >>> >>> /* we can use NODE_DATA(nid) from here */ >>> @@ -2021,15 +2025,6 @@ void try_offline_node(int nid) >>> >>> /* notify that the node is down */ >>> call_node_notify(NODE_DOWN, (void *)(long)nid); >>> - >>> - /* >>> - * Since there is no way to guarentee the address of pgdat/zone is not >>> - * on stack of any kernel threads or used by other kernel objects >>> - * without reference counting or other symchronizing method, do not >>> - * reset node_data and free pgdat here. Just reset it to 0 and reuse >>> - * the memory when the node is online again. >>> - */ >>> - memset(pgdat, 0, sizeof(*pgdat)); >>> } >>> EXPORT_SYMBOL(try_offline_node); >>> >> >> >> >> -- >> To unsubscribe, send a message with 'unsubscribe linux-mm' in >> the body to majordomo@kvack.org. For more info on Linux MM, >> see: http://www.linux-mm.org/ . >> Don't email: email@kvack.org >> . >> > > > -- > 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/ > > . > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org