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=-2.5 required=3.0 tests=MAILING_LIST_MULTI,SPF_PASS, USER_AGENT_MUTT 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 9B3F2C43142 for ; Mon, 25 Jun 2018 13:08:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 548B5259F7 for ; Mon, 25 Jun 2018 13:08:01 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 548B5259F7 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org 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 S1755538AbeFYNH7 (ORCPT ); Mon, 25 Jun 2018 09:07:59 -0400 Received: from mx2.suse.de ([195.135.220.15]:48066 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755221AbeFYNH6 (ORCPT ); Mon, 25 Jun 2018 09:07:58 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (charybdis-ext-too.suse.de [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id E04A0ACF9; Mon, 25 Jun 2018 13:07:56 +0000 (UTC) Date: Mon, 25 Jun 2018 15:07:56 +0200 From: Michal Hocko To: peter enderborg Cc: Tetsuo Handa , linux-mm@kvack.org, rientjes@google.com, akpm@linux-foundation.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm,oom: Bring OOM notifier callbacks to outside of OOM killer. Message-ID: <20180625130756.GK28965@dhcp22.suse.cz> References: <1529493638-6389-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp> <20180620115531.GL13685@dhcp22.suse.cz> <3d27f26e-68ba-d3c0-9518-cebeb2689aec@sony.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <3d27f26e-68ba-d3c0-9518-cebeb2689aec@sony.com> User-Agent: Mutt/1.9.5 (2018-04-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon 25-06-18 15:03:40, peter enderborg wrote: > 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.  It's even exported. What do you mean? oom_lock is certainly not exported for general use. It is not local to oom_killer.c just because it is needed in other _mm_ code. > >> 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. Just that lmk did it wrong doesn't mean others have to follow. -- Michal Hocko SUSE Labs