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=-0.9 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS 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 A3868ECE58E for ; Tue, 8 Oct 2019 10:04:36 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 6969321721 for ; Tue, 8 Oct 2019 10:04:36 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lca.pw header.i=@lca.pw header.b="MkG19wPi" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6969321721 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=lca.pw Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id E4B798E0005; Tue, 8 Oct 2019 06:04:35 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id DFC778E0003; Tue, 8 Oct 2019 06:04:35 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id CC3FC8E0005; Tue, 8 Oct 2019 06:04:35 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0138.hostedemail.com [216.40.44.138]) by kanga.kvack.org (Postfix) with ESMTP id B14768E0003 for ; Tue, 8 Oct 2019 06:04:35 -0400 (EDT) Received: from smtpin09.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with SMTP id 5B226824CA2A for ; Tue, 8 Oct 2019 10:04:35 +0000 (UTC) X-FDA: 76020182910.09.ghost81_ae5ac834e42f X-HE-Tag: ghost81_ae5ac834e42f X-Filterd-Recvd-Size: 3677 Received: from mail-qt1-f196.google.com (mail-qt1-f196.google.com [209.85.160.196]) by imf03.hostedemail.com (Postfix) with ESMTP for ; Tue, 8 Oct 2019 10:04:34 +0000 (UTC) Received: by mail-qt1-f196.google.com with SMTP id v52so1610392qtb.8 for ; Tue, 08 Oct 2019 03:04:34 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=lca.pw; s=google; h=content-transfer-encoding:from:mime-version:subject:date:message-id :references:cc:in-reply-to:to; bh=UHzh8Nd1pry2iT/DrbwRzV6vQa+dEjtAAEofF/MEC0w=; b=MkG19wPiUYEy/cwH4FWAdJFeOjxTx/ih3bRy9Ft9HUqflgmrO8W2P9pWqLKz1W1Wpo 4zCmrzjYfRzNZDjPMBjwwFbFQfUrBq/Lm/ioydz+tHPfFO671FqVrp8VT2kjhoOxP3kP j4COp8ThvUM1npokOcngJl8xj2iMg9P+Y+iI73OIqWpixBThtqR/uRWjyrWqxclnDhF4 DMdlK61gyjF41qEAfYtulkO1jWJAoqkOwpfRSJ3OAHgsoibpeTPqwXTkfk+LqLkMjVwm m19jghQDsgEo87ss6InPPapN9RqVbvm1QdD+vopuB+KnT1eS/j0iAaf35z7eLBC+ljI8 oZQg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:content-transfer-encoding:from:mime-version :subject:date:message-id:references:cc:in-reply-to:to; bh=UHzh8Nd1pry2iT/DrbwRzV6vQa+dEjtAAEofF/MEC0w=; b=IuCyrgfi8a/X/OcSxBT6wNvoCzbdISU3Xf1nLlZWuYolZ6+mlx/97gtGOEvTTIcJZB 2/JMn7lmwIF/VEyQQ+ViuVzsUJd9b1A1zb6GAqu5RI8E666aP8w4M8+uuI3G2AyjtYrK cyqcQN5SXRZGHwm3iJ9TtR9MMnR0o26nFSpOx85Vc3XJHsAvzz8eH7uawk4EOYz5mLPm mra1dJXdgRFESIphlTcXVs69gucWZ3KS+cLe/+gl9WUQzqbVp1MxHcsV4TtecOSNYRWU zOV73k67e9eSqJVBd+/ckRmE1nu/V6YFnkYH4Fw/oOPgGykQQRgIDEnqlujXVIkQck9F 1haA== X-Gm-Message-State: APjAAAVPcKtbQuAjZRdO3ls3aIlbi5NNplzpjhAQ61eWGgVeDqQjyU8r ryW2zu6Cv/N+PvG1v2mIDadP+A== X-Google-Smtp-Source: APXvYqw7c8QA+yozBt0uCvf/tfkuKfaIVAYplJEsYi/GpUQdwiDTaqs8uL3JR7XJ6WvUkOaVZ6eLnw== X-Received: by 2002:ac8:b41:: with SMTP id m1mr34691601qti.382.1570529074168; Tue, 08 Oct 2019 03:04:34 -0700 (PDT) Received: from [192.168.1.183] (pool-71-184-117-43.bstnma.fios.verizon.net. [71.184.117.43]) by smtp.gmail.com with ESMTPSA id a36sm9356107qtk.21.2019.10.08.03.04.33 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 08 Oct 2019 03:04:33 -0700 (PDT) Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable From: Qian Cai Mime-Version: 1.0 (1.0) Subject: Re: [PATCH v2] mm/page_isolation: fix a deadlock with printk() Date: Tue, 8 Oct 2019 06:04:32 -0400 Message-Id: <298970BD-529E-4095-8D87-61470ADBDD32@lca.pw> References: <20191008084031.GC6681@dhcp22.suse.cz> 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 In-Reply-To: <20191008084031.GC6681@dhcp22.suse.cz> To: Michal Hocko X-Mailer: iPhone Mail (17A860) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000002, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: > On Oct 8, 2019, at 4:40 AM, Michal Hocko wrote: >=20 > 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 loc= k orders everywhere. On the other hand, it make a little different to spend t= oo much time arguing the authentic of those reproducible locdep splats, as e= ven false positives could be as bad for developers where it would disable th= e whole lockdep and mask off other true deadlock could happen later.=