From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id CB3EDC004D3 for ; Mon, 22 Oct 2018 10:57:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8AABC20658 for ; Mon, 22 Oct 2018 10:57:11 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8AABC20658 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=i-love.sakura.ne.jp Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728791AbeJVTPN (ORCPT ); Mon, 22 Oct 2018 15:15:13 -0400 Received: from www262.sakura.ne.jp ([202.181.97.72]:39954 "EHLO www262.sakura.ne.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727857AbeJVTPN (ORCPT ); Mon, 22 Oct 2018 15:15:13 -0400 Received: from fsav104.sakura.ne.jp (fsav104.sakura.ne.jp [27.133.134.231]) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTP id w9MAuqVL046291; Mon, 22 Oct 2018 19:56:52 +0900 (JST) (envelope-from penguin-kernel@i-love.sakura.ne.jp) Received: from www262.sakura.ne.jp (202.181.97.72) by fsav104.sakura.ne.jp (F-Secure/fsigk_smtp/530/fsav104.sakura.ne.jp); Mon, 22 Oct 2018 19:56:52 +0900 (JST) X-Virus-Status: clean(F-Secure/fsigk_smtp/530/fsav104.sakura.ne.jp) Received: from [192.168.1.8] (softbank060157066051.bbtec.net [60.157.66.51]) (authenticated bits=0) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTPSA id w9MAupSs046287 (version=TLSv1.2 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Mon, 22 Oct 2018 19:56:52 +0900 (JST) (envelope-from penguin-kernel@i-love.sakura.ne.jp) Subject: Re: [RFC PATCH 1/2] mm, oom: marks all killed tasks as oom victims To: Michal Hocko Cc: linux-mm@kvack.org, Johannes Weiner , David Rientjes , Andrew Morton , LKML References: <20181022071323.9550-1-mhocko@kernel.org> <20181022071323.9550-2-mhocko@kernel.org> <201810220758.w9M7wojE016890@www262.sakura.ne.jp> <20181022084842.GW18839@dhcp22.suse.cz> <20181022104341.GY18839@dhcp22.suse.cz> From: Tetsuo Handa Message-ID: <93f99371-cff8-fc31-a594-eecdff299f16@i-love.sakura.ne.jp> Date: Mon, 22 Oct 2018 19:56:49 +0900 User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20181022104341.GY18839@dhcp22.suse.cz> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2018/10/22 19:43, Michal Hocko wrote: > On Mon 22-10-18 18:42:30, Tetsuo Handa wrote: >> On 2018/10/22 17:48, Michal Hocko wrote: >>> On Mon 22-10-18 16:58:50, Tetsuo Handa wrote: >>>> Michal Hocko wrote: >>>>> --- a/mm/oom_kill.c >>>>> +++ b/mm/oom_kill.c >>>>> @@ -898,6 +898,7 @@ static void __oom_kill_process(struct task_struct *victim) >>>>> if (unlikely(p->flags & PF_KTHREAD)) >>>>> continue; >>>>> do_send_sig_info(SIGKILL, SEND_SIG_FORCED, p, PIDTYPE_TGID); >>>>> + mark_oom_victim(p); >>>>> } >>>>> rcu_read_unlock(); >>>>> >>>>> -- >>>> >>>> Wrong. Either >>> >>> You are right. The mm might go away between process_shares_mm and here. >>> While your find_lock_task_mm would be correct I believe we can do better >>> by using the existing mm that we already have. I will make it a separate >>> patch to clarity. >> >> Still wrong. p->mm == NULL means that we are too late to set TIF_MEMDIE >> on that thread. Passing non-NULL mm to mark_oom_victim() won't help. > > Why would it be too late? Or in other words why would this be harmful? > Setting TIF_MEMDIE after exit_mm() completed is too late. static void exit_mm(void) { (...snipped...) task_lock(current); current->mm = NULL; up_read(&mm->mmap_sem); enter_lazy_tlb(mm, current); task_unlock(current); mm_update_next_owner(mm); mmput(mm); if (test_thread_flag(TIF_MEMDIE)) exit_oom_victim(); }