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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED 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 6C1E4C43441 for ; Fri, 23 Nov 2018 15:56:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3E68C20892 for ; Fri, 23 Nov 2018 15:56:40 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3E68C20892 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=goodmis.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2440461AbeKXClX (ORCPT ); Fri, 23 Nov 2018 21:41:23 -0500 Received: from mail.kernel.org ([198.145.29.99]:37298 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2436676AbeKXClX (ORCPT ); Fri, 23 Nov 2018 21:41:23 -0500 Received: from vmware.local.home (cpe-66-24-56-78.stny.res.rr.com [66.24.56.78]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 90362205C9; Fri, 23 Nov 2018 15:56:36 +0000 (UTC) Date: Fri, 23 Nov 2018 10:56:34 -0500 From: Steven Rostedt To: Petr Mladek Cc: Tetsuo Handa , Sergey Senozhatsky , Linus Torvalds , Sergey Senozhatsky , Dmitriy Vyukov , Alexander Potapenko , Fengguang Wu , Josh Poimboeuf , LKML , Andrew Morton , linux-mm@kvack.org, Ingo Molnar , Peter Zijlstra , Will Deacon Subject: Re: [PATCH 3/3] lockdep: Use line-buffered printk() for lockdep messages. Message-ID: <20181123105634.4956c255@vmware.local.home> In-Reply-To: <20181123124647.jmewvgrqdpra7wbm@pathway.suse.cz> References: <1541165517-3557-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp> <1541165517-3557-3-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp> <20181107151900.gxmdvx42qeanpoah@pathway.suse.cz> <20181108044510.GC2343@jagdpanzerIV> <9648a384-853c-942e-6a8d-80432d943aae@i-love.sakura.ne.jp> <20181109061204.GC599@jagdpanzerIV> <07dcbcb8-c5a7-8188-b641-c110ade1c5da@i-love.sakura.ne.jp> <20181109154326.apqkbsojmbg26o3b@pathway.suse.cz> <20181123124647.jmewvgrqdpra7wbm@pathway.suse.cz> X-Mailer: Claws Mail 3.15.1 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 23 Nov 2018 13:46:47 +0100 Petr Mladek wrote: > Steven told me on Plumbers conference that even few initial > characters saved him a day few times. Yes, and that has happened more than once. I would reboot and retest code that is crashing, and due to a triple fault, the machine would reboot because of some race, and the little output I get from the console would help tremendously. Remember, debugging the kernel is a lot like forensics, especially when it's from a customer's site. You look at all the evidence that you can get, and sometimes it's just 10 characters in the output that gives you an idea of where things went wrong. I'm really not liking the buffering idea because of this. -- Steve