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=-8.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_PASS,USER_AGENT_MUTT 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 EBBE1C04A6B for ; Mon, 13 May 2019 02:31:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AC560208C0 for ; Mon, 13 May 2019 02:31:56 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=joelfernandes.org header.i=@joelfernandes.org header.b="iRl0DBZn" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727331AbfEMCbz (ORCPT ); Sun, 12 May 2019 22:31:55 -0400 Received: from mail-pl1-f193.google.com ([209.85.214.193]:43237 "EHLO mail-pl1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727311AbfEMCby (ORCPT ); Sun, 12 May 2019 22:31:54 -0400 Received: by mail-pl1-f193.google.com with SMTP id n8so5643050plp.10 for ; Sun, 12 May 2019 19:31:54 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=joelfernandes.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=GkmKn8xqtM5ZFNASHy3dhSS1TrKNKE1jNN1/7Rw3UKs=; b=iRl0DBZnB84iNuFBTLWCeRyIpe0lPSsH15HCK6R6QA+PwO8exC1hHVjRgytri52y0q AOdcHrBnb8unRWbDBfXAac3xtO2Pq/ni2zHg2H9doeRN/YbHX4x5lt0Z3vp3M99NadxD E9/XMC0G2cO9/StbBL2Yw3EU2hvkVISGiw84w= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=GkmKn8xqtM5ZFNASHy3dhSS1TrKNKE1jNN1/7Rw3UKs=; b=HMBGS8EHiJSojkx1mwhexseke8TbQyEB1ySoXjq+l1ABUcZr+myml6GTLbLDuwNWG+ V01O1Zg3GcxWvEY8SBxz9rKnEuGlM2NJbjxaKhTeSSq7UQVxw0NJGd9w6pmvu9mdHCE7 JouA0/8A1BB09z2iJhnvCsmsitoFwy2l/MQO6AiEQRKGJ+lSdALedwkoujw9kxxdOr4o 1YXycelBNYKqFZvNwDgQc0zRdxKbfSjCYdBh8iQ7K89HHZyOVV4JVeTGcUV70Vt5WKFb rfYVbMtEYs8T2sUTneNKCgy/hXhYJiuJs12pG0FOIwC2pHlwPCUfnozFGMK8o3Z/kqBr aZkg== X-Gm-Message-State: APjAAAWgwK36mzKKIBzrnvWsb0Vmtkm0fb/4BciML9My8bi8HcNS6hpC PmabX3dcHNhf003xczCwlqU1Rw== X-Google-Smtp-Source: APXvYqxM3LbMIU9Q5iaT+nkjQfWHuEDGndPZntXzyCbgcmkhL7NypAv9mABJvVEnP0bGD1ZenD85DQ== X-Received: by 2002:a17:902:7406:: with SMTP id g6mr27017388pll.328.1557714713660; Sun, 12 May 2019 19:31:53 -0700 (PDT) Received: from localhost ([2620:15c:6:12:9c46:e0da:efbf:69cc]) by smtp.gmail.com with ESMTPSA id y14sm13984506pga.54.2019.05.12.19.31.51 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Sun, 12 May 2019 19:31:52 -0700 (PDT) Date: Sun, 12 May 2019 22:31:50 -0400 From: Joel Fernandes To: Steven Rostedt Cc: Zhenzhong Duan , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, paulmck@linux.ibm.com, josh@joshtriplett.org, mathieu.desnoyers@efficios.com, jiangshanlai@gmail.com, corbet@lwn.net, tglx@linutronix.de, mingo@kernel.org, gregkh@linuxfoundation.org, keescook@chromium.org, srinivas.eeda@oracle.com Subject: Re: [PATCH 2/2] doc: kernel-parameters.txt: fix documentation of nmi_watchdog parameter Message-ID: <20190513023150.GA192545@google.com> References: <1555211464-28652-1-git-send-email-zhenzhong.duan@oracle.com> <1555211464-28652-2-git-send-email-zhenzhong.duan@oracle.com> <20190510144749.592f4249@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190510144749.592f4249@gandalf.local.home> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, May 10, 2019 at 02:47:49PM -0400, Steven Rostedt wrote: > > As nobody else commented, I will ;) > > Hi Zhenzhong! > > On Sun, 14 Apr 2019 11:11:04 +0800 > Zhenzhong Duan wrote: > > > As stated in "Documentation/lockup-watchdogs.txt:line 22", the default > > behaivor after 'hardlockup' is to stay locked up rather than panic. > > That actually says: > > A 'hardlockup' is defined as a bug that causes the CPU to loop in > kernel mode for more than 10 seconds (see "Implementation" below for > details), without letting other interrupts have a chance to run. > Similarly to the softlockup case, the current stack trace is displayed > upon detection and the system will stay locked up unless the default > behavior is changed, which can be done through a sysctl, > 'hardlockup_panic', a compile time knob, "BOOTPARAM_HARDLOCKUP_PANIC", > and a kernel parameter, "nmi_watchdog" > > If your config has: > > CONFIG_BOOTPARAM_HARDLOCKUP_PANIC=y > > The kernel will panic on hard lockup by default unless you add nopanic. > > If your config has: > > # CONFIG_BOOTPARAM_HARDLOCKUP_PANIC is not set > > Then the default will be not to panic unless you add "panic" to the > kernel command line. > > > > > Signed-off-by: Zhenzhong Duan > > --- > > Documentation/admin-guide/kernel-parameters.txt | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt > > index 2b8ee90..fcc9579 100644 > > --- a/Documentation/admin-guide/kernel-parameters.txt > > +++ b/Documentation/admin-guide/kernel-parameters.txt > > @@ -2769,7 +2769,7 @@ > > 0 - turn hardlockup detector in nmi_watchdog off > > 1 - turn hardlockup detector in nmi_watchdog on > > When panic is specified, panic when an NMI watchdog > > - timeout occurs (or 'nopanic' to override the opposite > > + timeout occurs (or 'nopanic' which is the opposite > > default). To disable both hard and soft lockup detectors, > > Honestly, I think the original text states what it does better than > your update. Because the nopanic is added to override the "opposite > default" which is if the config was set to do so. > > That said, this all still can be explained better. What about: > > nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels > Format: [panic,][nopanic,][num] > Valid num: 0 or 1 > 0 - turn hardlockup detector in nmi_watchdog off > 1 - turn hardlockup detector in nmi_watchdog on > When panic is specified, panic when an NMI watchdog > timeout occurs (or 'nopanic' to not panic on an NMI > watchdog, if CONFIG_BOOTPARAM_HARDLOCKUP_PANIC is set) > To disable both hard and soft lockup detectors, > please see 'nowatchdog'. > This is useful when you use a panic=... timeout and > need the box quickly up again. Steven, your update makes it more clear to me. If patch is being written with such update, here is my Reviewed-by: Reviewed-by: Joel Fernandes (Google) thanks! - Joel > > -- Steve > > > > please see 'nowatchdog'. > > This is useful when you use a panic=... timeout and >