From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752207AbcFUQcB (ORCPT ); Tue, 21 Jun 2016 12:32:01 -0400 Received: from mail-lf0-f68.google.com ([209.85.215.68]:35452 "EHLO mail-lf0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752578AbcFUQb7 (ORCPT ); Tue, 21 Jun 2016 12:31:59 -0400 Date: Tue, 21 Jun 2016 18:29:20 +0300 From: "Kirill A. Shutemov" To: zhong jiang Cc: mhocko@kernel.org, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/huge_memory: fix the memory leak due to the race Message-ID: <20160621152920.GA7760@node.shutemov.name> References: <1466517956-13875-1-git-send-email-zhongjiang@huawei.com> <20160621143701.GA6139@node.shutemov.name> <57695AEB.8030509@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <57695AEB.8030509@huawei.com> User-Agent: Mutt/1.5.23.1 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jun 21, 2016 at 11:19:07PM +0800, zhong jiang wrote: > On 2016/6/21 22:37, Kirill A. Shutemov wrote: > > On Tue, Jun 21, 2016 at 10:05:56PM +0800, zhongjiang wrote: > >> From: zhong jiang > >> > >> with great pressure, I run some test cases. As a result, I found > >> that the THP is not freed, it is detected by check_mm(). > >> > >> BUG: Bad rss-counter state mm:ffff8827edb70000 idx:1 val:512 > >> > >> Consider the following race : > >> > >> CPU0 CPU1 > >> __handle_mm_fault() > >> wp_huge_pmd() > >> do_huge_pmd_wp_page() > >> pmdp_huge_clear_flush_notify() > >> (pmd_none = true) > >> exit_mmap() > >> unmap_vmas() > >> zap_pmd_range() > >> pmd_none_or_trans_huge_or_clear_bad() > >> (result in memory leak) > >> set_pmd_at() > >> > >> because of CPU0 have allocated huge page before pmdp_huge_clear_notify, > >> and it make the pmd entry to be null. Therefore, The memory leak can occur. > >> > >> The patch fix the scenario that the pmd entry can lead to be null. > > I don't think the scenario is possible. > > > > exit_mmap() called when all mm users have gone, so no parallel threads > > exist. > > > Forget this patch. It 's my fault , it indeed don not exist. > But I hit the following problem. we can see the memory leak when the process exit. > > > Any suggestion will be apprecaited. Could you try this: http://lkml.kernel.org/r/20160621150433.GA7536@node.shutemov.name -- Kirill A. Shutemov