From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-oi0-f72.google.com (mail-oi0-f72.google.com [209.85.218.72]) by kanga.kvack.org (Postfix) with ESMTP id 410676B0253 for ; Mon, 27 Jun 2016 22:35:36 -0400 (EDT) Received: by mail-oi0-f72.google.com with SMTP id d132so5992643oig.0 for ; Mon, 27 Jun 2016 19:35:36 -0700 (PDT) Received: from szxga01-in.huawei.com (szxga01-in.huawei.com. [58.251.152.64]) by mx.google.com with ESMTPS id t13si12764586ott.132.2016.06.27.19.35.34 for (version=TLS1 cipher=AES128-SHA bits=128/128); Mon, 27 Jun 2016 19:35:35 -0700 (PDT) Message-ID: <5771E25C.10605@huawei.com> Date: Tue, 28 Jun 2016 10:35:08 +0800 From: zhong jiang MIME-Version: 1.0 Subject: Re: A question about the patch(commit :c777e2a8b654 powerpc/mm: Fix Multi hit ERAT cause by recent THP update) References: <576AA934.4090504@huawei.com> <20160623092946.GA30082@dhcp22.suse.cz> <20160623093411.GB30077@dhcp22.suse.cz> In-Reply-To: <20160623093411.GB30077@dhcp22.suse.cz> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: aneesh.kumar@linux.vnet.ibm.com, Linux Memory Management List On 2016/6/23 17:34, Michal Hocko wrote: > On Thu 23-06-16 11:29:46, Michal Hocko wrote: >> On Wed 22-06-16 23:05:24, zhong jiang wrote: >>> Hi Aneesh >>> >>> CPU0 CPU1 >>> shrink_page_list() >>> add_to_swap() >>> split_huge_page_to_list() >>> __split_huge_pmd_locked() >>> pmdp_huge_clear_flush_notify() >>> // pmd_none() == true >>> exit_mmap() >>> unmap_vmas() >>> zap_pmd_range() >>> // no action on pmd since pmd_none() == true >>> pmd_populate() >>> >>> >>> the mm should be the last user when CPU1 process is exiting, CPU0 must be a own mm . >>> two different process should not be influenced each other. in a words , they should not >>> have race. >> No this is a different scenario than >> http://lkml.kernel.org/r/1466517956-13875-1-git-send-email-zhongjiang@huawei.com >> we were discussing recently. Note that pages are still on the LRU lists >> while the mm which maps them is exiting. So the above race is very much >> possible. > And just to clarify, I haven't checked the current code after c777e2a8b654 > ("powerpc/mm: Fix Multi hit ERAT cause by recent THP update") which is > ppc specific and I have no idea whether other arches need a similar > treatment. I was merely trying to explain that the mm exclusive argument > doesn't apply to reclaim vs. exit races. Thank for your explaintion! -- 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