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 5784FC10F14 for ; Tue, 8 Oct 2019 10:39:12 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 3126B206C2 for ; Tue, 8 Oct 2019 10:39:12 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3126B206C2 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 C840B8E0005; Tue, 8 Oct 2019 06:39:11 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id C34F68E0003; Tue, 8 Oct 2019 06:39:11 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id B4AA28E0005; Tue, 8 Oct 2019 06:39:11 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0211.hostedemail.com [216.40.44.211]) by kanga.kvack.org (Postfix) with ESMTP id 96BF48E0003 for ; Tue, 8 Oct 2019 06:39:11 -0400 (EDT) Received: from smtpin12.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with SMTP id 38E4D180AD806 for ; Tue, 8 Oct 2019 10:39:11 +0000 (UTC) X-FDA: 76020270102.12.able40_15f5c4339a311 X-HE-Tag: able40_15f5c4339a311 X-Filterd-Recvd-Size: 1635 Received: from mx1.suse.de (mx2.suse.de [195.135.220.15]) by imf40.hostedemail.com (Postfix) with ESMTP for ; Tue, 8 Oct 2019 10:39:10 +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 EB0CFAEAF; Tue, 8 Oct 2019 10:39:08 +0000 (UTC) Date: Tue, 8 Oct 2019 12:39:07 +0200 From: Michal Hocko To: Qian Cai Cc: Petr Mladek , akpm@linux-foundation.org, sergey.senozhatsky.work@gmail.com, rostedt@goodmis.org, peterz@infradead.org, linux-mm@kvack.org, john.ogness@linutronix.de, david@redhat.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] mm/page_isolation: fix a deadlock with printk() Message-ID: <20191008103907.GE6681@dhcp22.suse.cz> References: <20191008084031.GC6681@dhcp22.suse.cz> <298970BD-529E-4095-8D87-61470ADBDD32@lca.pw> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <298970BD-529E-4095-8D87-61470ADBDD32@lca.pw> User-Agent: Mutt/1.10.1 (2018-07-13) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000058, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue 08-10-19 06:04:32, Qian Cai wrote: > > > > On Oct 8, 2019, at 4:40 AM, Michal Hocko wrote: > > > > Does this tip point to a real deadlock or merely a class of lockdep > > false dependencies? > > I lean towards it is a real deadlock given how trivial to generate those lock orders everywhere. Have you actually triggered any real deadlock? With a zone->lock in place it would be pretty clear with hard lockups detected. -- Michal Hocko SUSE Labs