From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lf0-f72.google.com (mail-lf0-f72.google.com [209.85.215.72]) by kanga.kvack.org (Postfix) with ESMTP id 973016B0005 for ; Mon, 25 Jun 2018 09:03:43 -0400 (EDT) Received: by mail-lf0-f72.google.com with SMTP id f126-v6so3967049lfg.5 for ; Mon, 25 Jun 2018 06:03:43 -0700 (PDT) Received: from SELDSEGREL01.sonyericsson.com (seldsegrel01.sonyericsson.com. [37.139.156.29]) by mx.google.com with ESMTPS id z13-v6si5773642lff.54.2018.06.25.06.03.41 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 25 Jun 2018 06:03:41 -0700 (PDT) Subject: Re: [PATCH] mm,oom: Bring OOM notifier callbacks to outside of OOM killer. References: <1529493638-6389-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp> <20180620115531.GL13685@dhcp22.suse.cz> From: peter enderborg Message-ID: <3d27f26e-68ba-d3c0-9518-cebeb2689aec@sony.com> Date: Mon, 25 Jun 2018 15:03:40 +0200 MIME-Version: 1.0 In-Reply-To: <20180620115531.GL13685@dhcp22.suse.cz> Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Content-Language: en-GB Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko , Tetsuo Handa Cc: linux-mm@kvack.org, rientjes@google.com, akpm@linux-foundation.org, linux-kernel@vger.kernel.org On 06/20/2018 01:55 PM, Michal Hocko wrote: > On Wed 20-06-18 20:20:38, Tetsuo Handa wrote: >> Sleeping with oom_lock held can cause AB-BA lockup bug because >> __alloc_pages_may_oom() does not wait for oom_lock. Since >> blocking_notifier_call_chain() in out_of_memory() might sleep, sleeping >> with oom_lock held is currently an unavoidable problem. > Could you be more specific about the potential deadlock? Sleeping while > holding oom lock is certainly not nice but I do not see how that would > result in a deadlock assuming that the sleeping context doesn't sleep on > the memory allocation obviously. It is a mutex you are supposed to be able to sleep.=C2=A0 It's even exporte= d. >> As a preparation for not to sleep with oom_lock held, this patch brings >> OOM notifier callbacks to outside of OOM killer, with two small behavior >> changes explained below. > Can we just eliminate this ugliness and remove it altogether? We do not > have that many notifiers. Is there anything fundamental that would > prevent us from moving them to shrinkers instead? @Hocko Do you remember the lowmemorykiller from android? Some things might = not be the right thing for shrinkers.