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=-2.4 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_2 autolearn=no 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 92A09C4360C for ; Thu, 10 Oct 2019 14:47:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 62FBB21835 for ; Thu, 10 Oct 2019 14:47:44 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lca.pw header.i=@lca.pw header.b="miW/7gsG" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726402AbfJJOrn (ORCPT ); Thu, 10 Oct 2019 10:47:43 -0400 Received: from mail-qk1-f194.google.com ([209.85.222.194]:43676 "EHLO mail-qk1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725867AbfJJOrm (ORCPT ); Thu, 10 Oct 2019 10:47:42 -0400 Received: by mail-qk1-f194.google.com with SMTP id h126so5821066qke.10 for ; Thu, 10 Oct 2019 07:47:42 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=lca.pw; s=google; h=message-id:subject:from:to:cc:date:in-reply-to:references :mime-version:content-transfer-encoding; bh=dY3cxBFbn5BFQR3wtmZXnj2xekyjm05rgtTqVfByDnk=; b=miW/7gsGehxbucNWUNf+JQQBZuBtJ2eE0qM4yM0DCDw4cxXTcso32P45cl8wkFq2aV QiAzEX8SfUjgqSnOp3xq9j/NJYHOlrYkv0vzUZ2SiNP/GRVGUpnKcCBh7bRerWjIlGfw f9hLXoCL2l9oLKJ8nNLr3d9TVtxohQRIk65qwUMO2cUWjc2AlMt4bULOYdg5daeZYvGi fb7rVgBALWWubKCC0Hh4ezsT0yQl2avWYlBCFlUTGabe0tkEO6snRU6NDw1vg8ebTLSO XqJOybJAHXF+aNu2td0emR0oOpgjJ28ENqxR8D6ivWvfSXcamA1hqcD5DogH1QcRwuhZ MQWA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:message-id:subject:from:to:cc:date:in-reply-to :references:mime-version:content-transfer-encoding; bh=dY3cxBFbn5BFQR3wtmZXnj2xekyjm05rgtTqVfByDnk=; b=JX0JA08MMzOB19rJK/ZHZJletCx+8exLtnxrVV6HHff7oHtCJYJj3mn71KIQWi3Khu m5DV/NeNh65Rh22MbmhWuhJmccembo1jYOUxfkgs6mVoph1vQ5czBqnplShUgy032dIe 8yQMujop8z8zBeLgfWC113t/61sBvFGnDAO4SXLX9OVgQKpvi/MREJ5po15rc+AzIH9P fyHGQybetnt7VsTNfPnoZoVZv6DWSvxzeDA4OF97EHXMoIdU+tvK2hiIBk8Z/cb6cy+u HX0gXkRmjqtLvoKDu0CmoR2WQ05KiBO0zUM+rTwYfWCdPgz1TCpfxO9Vd6xY42lz9zmt eKkg== X-Gm-Message-State: APjAAAUzcAeYGgk8JRjIwA9HP4SSgv1btnAxGcEkuDkwOrsRDttOYzzt AEjZgrgam20R7fqAAH1h3TYcsA== X-Google-Smtp-Source: APXvYqzuGVYLmfVHrpebW8KExt+KSlXKe3bxkKadjMlG+hrolzAg5Lm0HAeVpSLnhiERXxK/ZtkJ6w== X-Received: by 2002:a37:9847:: with SMTP id a68mr10359301qke.223.1570718861606; Thu, 10 Oct 2019 07:47:41 -0700 (PDT) Received: from dhcp-41-57.bos.redhat.com (nat-pool-bos-t.redhat.com. [66.187.233.206]) by smtp.gmail.com with ESMTPSA id f27sm2366449qkh.42.2019.10.10.07.47.39 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 10 Oct 2019 07:47:40 -0700 (PDT) Message-ID: <1570718858.5937.28.camel@lca.pw> Subject: Re: [PATCH v2] mm/page_isolation: fix a deadlock with printk() From: Qian Cai To: Michal Hocko Cc: Petr Mladek , Christian Borntraeger , Heiko Carstens , sergey.senozhatsky.work@gmail.com, rostedt@goodmis.org, peterz@infradead.org, linux-mm@kvack.org, john.ogness@linutronix.de, akpm@linux-foundation.org, Vasily Gorbik , Peter Oberparleiter , david@redhat.com, linux-kernel@vger.kernel.org Date: Thu, 10 Oct 2019 10:47:38 -0400 In-Reply-To: <20191010141820.GI18412@dhcp22.suse.cz> References: <20191009162339.GI6681@dhcp22.suse.cz> <6AAB77B5-092B-43E3-9F4B-0385DE1890D9@lca.pw> <20191010105927.GG18412@dhcp22.suse.cz> <1570713112.5937.26.camel@lca.pw> <20191010141820.GI18412@dhcp22.suse.cz> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.22.6 (3.22.6-10.el7) Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2019-10-10 at 16:18 +0200, Michal Hocko wrote: > On Thu 10-10-19 09:11:52, Qian Cai wrote: > > On Thu, 2019-10-10 at 12:59 +0200, Michal Hocko wrote: > > > On Thu 10-10-19 05:01:44, Qian Cai wrote: > > > > > > > > > > > > > On Oct 9, 2019, at 12:23 PM, Michal Hocko wrote: > > > > > > > > > > If this was only about the memory offline code then I would agree. But > > > > > we are talking about any printk from the zone->lock context and that is > > > > > a bigger deal. Besides that it is quite natural that the printk code > > > > > should be more universal and allow to be also called from the MM > > > > > contexts as much as possible. If there is any really strong reason this > > > > > is not possible then it should be documented at least. > > > > > > > > Where is the best place to document this? I am thinking about under > > > > the “struct zone” definition’s lock field in mmzone.h. > > > > > > I am not sure TBH and I do not think we have reached the state where > > > this would be the only way forward. > > > > How about I revised the changelog to focus on memory offline rather than making > > a rule that nobody should call printk() with zone->lock held? > > If you are to remove the CONFIG_DEBUG_VM printk then I am all for it. I > am still not convinced that fiddling with dump_page in the isolation > code is justified though. No, dump_page() there has to be fixed together for memory offline to be useful. What's the other options it has here? By not holding zone->lock in dump_page() from set_migratetype_isolate(), it even has a good side-effect to increase the system throughput as dump_page() could be time-consuming. It may make the code a bit cleaner by introducing a has_unmovable_pages_locked() version.