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_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 80785ECE58E for ; Thu, 10 Oct 2019 14:18:28 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 455C020B7C for ; Thu, 10 Oct 2019 14:18:28 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 455C020B7C Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id CE6D96B0005; Thu, 10 Oct 2019 10:18:27 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id C966F6B0006; Thu, 10 Oct 2019 10:18:27 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id B5DBC8E0003; Thu, 10 Oct 2019 10:18:27 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0085.hostedemail.com [216.40.44.85]) by kanga.kvack.org (Postfix) with ESMTP id 8D5886B0005 for ; Thu, 10 Oct 2019 10:18:27 -0400 (EDT) Received: from smtpin11.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with SMTP id 34AC5180AD807 for ; Thu, 10 Oct 2019 14:18:27 +0000 (UTC) X-FDA: 76028080254.11.anger38_f8d2abe82159 X-HE-Tag: anger38_f8d2abe82159 X-Filterd-Recvd-Size: 2756 Received: from mx1.suse.de (mx2.suse.de [195.135.220.15]) by imf02.hostedemail.com (Postfix) with ESMTP for ; Thu, 10 Oct 2019 14:18:26 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id ECE46B469; Thu, 10 Oct 2019 14:18:24 +0000 (UTC) Date: Thu, 10 Oct 2019 16:18:20 +0200 From: Michal Hocko To: Qian Cai 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 Subject: Re: [PATCH v2] mm/page_isolation: fix a deadlock with printk() Message-ID: <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> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <1570713112.5937.26.camel@lca.pw> User-Agent: Mutt/1.10.1 (2018-07-13) Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000242, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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: > > >=20 > > >=20 > > > > On Oct 9, 2019, at 12:23 PM, Michal Hocko wro= te: > > > >=20 > > > > 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 t= hat is > > > > a bigger deal. Besides that it is quite natural that the printk c= ode > > > > should be more universal and allow to be also called from the MM > > > > contexts as much as possible. If there is any really strong reaso= n this > > > > is not possible then it should be documented at least. > > >=20 > > > Where is the best place to document this? I am thinking about under > > > the =E2=80=9Cstruct zone=E2=80=9D definition=E2=80=99s lock field i= n mmzone.h. > >=20 > > I am not sure TBH and I do not think we have reached the state where > > this would be the only way forward. >=20 > How about I revised the changelog to focus on memory offline rather tha= n 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. --=20 Michal Hocko SUSE Labs