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=-13.4 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL 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 6125DC433E0 for ; Mon, 18 May 2020 12:44:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 38C66207D8 for ; Mon, 18 May 2020 12:44:29 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="CE/lKTEp" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727036AbgERMo2 (ORCPT ); Mon, 18 May 2020 08:44:28 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41172 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726855AbgERMo0 (ORCPT ); Mon, 18 May 2020 08:44:26 -0400 Received: from mail-ot1-x343.google.com (mail-ot1-x343.google.com [IPv6:2607:f8b0:4864:20::343]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EDA18C061A0C for ; Mon, 18 May 2020 05:44:25 -0700 (PDT) Received: by mail-ot1-x343.google.com with SMTP id c3so7847783otr.12 for ; Mon, 18 May 2020 05:44:25 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=mTr78JEsRcOgBqxtDKga7we0yjXSTYq9V0GCD/PQUyg=; b=CE/lKTEpgYM+eYNrcA3Ul2PeORNYAihMtIUSAUQzxTlgCD13y2KcsoH6GD5VjDKKNR Ody6r93SEfNyo5hY140gdOHy4FqjrYIbdQ8hMEY6vtZs6N7SsSER9uPCGE/yE922OQCD ZF/ppEjVO7h0GHNRPGcvLt8407BUq3nCM6m7w9Lb9r1rZZjNMnhnRgA38osD5gY4DlBW x6LZZogX9Y20y0SekHeIVXr2MlweNiNCFTUfGK4jpMipRHNCSnKZupnd9ji6JX179tie Q6nOTKxIOeoap5TYYHhoTBQZQ4oWvssd/SVXkRhmkid/u1F//otjI0LuWfrpamEcBmmX Y+gQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=mTr78JEsRcOgBqxtDKga7we0yjXSTYq9V0GCD/PQUyg=; b=BciJx+mfv1ZflDvZte6YUmk4oMEx9M+PjrvvhNu2hE+/dTZdmGzofoDncJPnByGvh0 QYqCmtJ/tbgB/HAsFebzpEW+YZ4H6WVgGwCo3K8i05oqL2tmyQ6Tc76UtLx67X9Ln4W7 mcCs88nu+QC0Bf4qI4BbrtMdy7OpjBi32eFWI1CoWWU+YH9gQA+MozUQCAuB13ATleCi fND1oSgDlxQ428F9GOG89KKie9worTiSWOU8h2ZdwnhFnTjBN0rmWqDar/f18xgehohs 2Mb9Y+8l+cxryp1GiGe7xHEtMw7ehBnVttvkrYOXCDfn5OYhGPgdRFg7JqvALpkePmAK RUKA== X-Gm-Message-State: AOAM532ONM/1vOUTAcFdE/UzLiW47HdVmhyb6iocXtptm7dZEY46QjlS F8PW0WzV5gVBZ80b9yj8BqQwhpRXI5meRqNqZp2S0w== X-Google-Smtp-Source: ABdhPJwPvMfYvq+F8WYaycOD8ztBRh6nouC6YLOhckJHzcj/zHjFs5D9P695EYaTVOD9n7NlLvtY4uqWYhuUFB5kdYA= X-Received: by 2002:a9d:7608:: with SMTP id k8mr12982752otl.233.1589805865139; Mon, 18 May 2020 05:44:25 -0700 (PDT) MIME-Version: 1.0 References: <20200517011732.GE24705@shao2-debian> <20200517034739.GO2869@paulmck-ThinkPad-P72> In-Reply-To: From: Marco Elver Date: Mon, 18 May 2020 14:44:13 +0200 Message-ID: Subject: Re: [rcu] 2f08469563: BUG:kernel_reboot-without-warning_in_boot_stage To: "Paul E. McKenney" , kan.liang@linux.intel.com, Peter Zijlstra , clang-built-linux , Nick Desaulniers Cc: kernel test robot , LKML , LKP Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org [+Cc clang-built-linux FYI] On Mon, 18 May 2020 at 12:11, Marco Elver wrote: > > On Sun, 17 May 2020 at 05:47, Paul E. McKenney wrote: > > > > On Sun, May 17, 2020 at 09:17:32AM +0800, kernel test robot wrote: > > > Greeting, > > > > > > FYI, we noticed the following commit (built with clang-11): > > > > > > commit: 2f08469563550d15cb08a60898d3549720600eee ("rcu: Mark rcu_state.ncpus to detect concurrent writes") > > > https://git.kernel.org/cgit/linux/kernel/git/paulmck/linux-rcu.git dev.2020.05.14c > > > > > > in testcase: boot > > > > > > on test machine: qemu-system-x86_64 -enable-kvm -cpu SandyBridge -smp 2 -m 8G > > > > > > caused below changes (please refer to attached dmesg/kmsg for entire log/backtrace): > > > > > > > > > > > > > > > If you fix the issue, kindly add following tag > > > Reported-by: kernel test robot > > > > > > > > > [ 0.054943] BRK [0x05204000, 0x05204fff] PGTABLE > > > [ 0.061181] BRK [0x05205000, 0x05205fff] PGTABLE > > > [ 0.062403] BRK [0x05206000, 0x05206fff] PGTABLE > > > [ 0.065200] RAMDISK: [mem 0x7a247000-0x7fffffff] > > > [ 0.067344] ACPI: Early table checksum verification disabled > > > BUG: kernel reboot-without-warning in boot stage > > > > I am having some difficulty believing that this commit is at fault given > > that the .config does not list CONFIG_KCSAN=y, but CCing Marco Elver > > for his thoughts. Especially given that I have never built with clang-11. > > > > But this does invoke ASSERT_EXCLUSIVE_WRITER() in early boot from > > rcu_init(). Might clang-11 have objections to early use of this macro? > > The macro is a noop without KCSAN. I think the bisection went wrong. > > I am able to reproduce a reboot-without-warning when building with > Clang 11 and the provided config. I did a bisect, starting with v5.6 > (good), and found this: > - Since v5.6, first bad commit is > 20e2aa812620439d010a3f78ba4e05bc0b3e2861 (Merge tag > 'perf-urgent-2020-04-12' of > git://git.kernel.org/pub/scm/linux/kernel//git/tip/tip) > - The actual commit that introduced the problem is > 2b3b76b5ec67568da4bb475d3ce8a92ef494b5de (perf/x86/intel/uncore: Add > Ice Lake server uncore support) -- reverting it fixes the problem. > > Thanks, > -- Marco