From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf1-f199.google.com (mail-pf1-f199.google.com [209.85.210.199]) by kanga.kvack.org (Postfix) with ESMTP id 6EFD06B18A3 for ; Mon, 20 Aug 2018 07:10:19 -0400 (EDT) Received: by mail-pf1-f199.google.com with SMTP id j15-v6so7690027pfi.10 for ; Mon, 20 Aug 2018 04:10:19 -0700 (PDT) Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id z187-v6si8191374pgd.618.2018.08.20.04.10.18 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 20 Aug 2018 04:10:18 -0700 (PDT) Date: Mon, 20 Aug 2018 13:10:15 +0200 From: Michal Hocko Subject: Re: [PATCH] mm, oom: OOM victims do not need to select next OOM victim unless __GFP_NOFAIL. Message-ID: <20180820111015.GL29735@dhcp22.suse.cz> References: <1534761465-6449-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp> <20180820105336.GJ29735@dhcp22.suse.cz> <1341c62b-cb21-a592-f062-d162da01f912@i-love.sakura.ne.jp> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1341c62b-cb21-a592-f062-d162da01f912@i-love.sakura.ne.jp> Sender: owner-linux-mm@kvack.org List-ID: To: Tetsuo Handa Cc: Andrew Morton , Dmitry Vyukov , linux-mm@kvack.org, Greg Thelen , David Rientjes , syzbot On Mon 20-08-18 20:02:30, Tetsuo Handa wrote: > On 2018/08/20 19:53, Michal Hocko wrote: > > On Mon 20-08-18 19:37:45, Tetsuo Handa wrote: > >> Commit 696453e66630ad45 ("mm, oom: task_will_free_mem should skip > >> oom_reaped tasks") changed to select next OOM victim as soon as > >> MMF_OOM_SKIP is set. But since OOM victims can try ALLOC_OOM allocation > >> and then give up (if !memcg OOM) or can use forced charge and then retry > >> (if memcg OOM), OOM victims do not need to select next OOM victim unless > >> they are doing __GFP_NOFAIL allocations. > > > > I do not like this at all. It seems hackish to say the least. And more > > importantly... > > > >> This is a quick mitigation because syzbot is hitting WARN(1) caused by > >> this race window [1]. More robust fix (e.g. make it possible to reclaim > >> more memory before MMF_OOM_SKIP is set, wait for some more after > >> MMF_OOM_SKIP is set) is a future work. > > > > .. there is already a patch (by Johannes) for that warning IIRC. > > You mean http://lkml.kernel.org/r/20180808144515.GA9276@cmpxchg.org ? Yes > But I can't find that patch in linux-next.git . And as far as I know, > no patch was sent to linux.git for handling this problem. Therefore, > I wrote this patch so that we can apply for 4.19-rc1. I am pretty sure Johannes will post them later after merge window closes. -- Michal Hocko SUSE Labs