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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS 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 0F543C3279B for ; Tue, 10 Jul 2018 21:40:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B888B208E5 for ; Tue, 10 Jul 2018 21:40:38 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B888B208E5 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=i-love.sakura.ne.jp 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 S1732333AbeGJVlg (ORCPT ); Tue, 10 Jul 2018 17:41:36 -0400 Received: from www262.sakura.ne.jp ([202.181.97.72]:24170 "EHLO www262.sakura.ne.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732187AbeGJVlg (ORCPT ); Tue, 10 Jul 2018 17:41:36 -0400 Received: from fsav104.sakura.ne.jp (fsav104.sakura.ne.jp [27.133.134.231]) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTP id w6AL8Kim082080; Wed, 11 Jul 2018 06:08:20 +0900 (JST) (envelope-from penguin-kernel@i-love.sakura.ne.jp) Received: from www262.sakura.ne.jp (202.181.97.72) by fsav104.sakura.ne.jp (F-Secure/fsigk_smtp/530/fsav104.sakura.ne.jp); Wed, 11 Jul 2018 06:08:19 +0900 (JST) X-Virus-Status: clean(F-Secure/fsigk_smtp/530/fsav104.sakura.ne.jp) Received: from [192.168.1.8] (softbank126074194044.bbtec.net [126.74.194.44]) (authenticated bits=0) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTPSA id w6AL8EmB082058 (version=TLSv1.2 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Wed, 11 Jul 2018 06:08:19 +0900 (JST) (envelope-from penguin-kernel@i-love.sakura.ne.jp) Subject: Re: [PATCH] x86: Avoid pr_cont() in show_opcodes() To: David Laight , "'Josh Poimboeuf'" , Peter Zijlstra Cc: Ingo Molnar , "mingo@redhat.com" , "linux-kernel@vger.kernel.org" , Andy Lutomirski , Borislav Petkov , Linus Torvalds , Thomas Gleixner References: <1530943625-3288-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp> <20180707111209.GA27768@gmail.com> <20180709084953.GB2476@hirez.programming.kicks-ass.net> <20180709191034.pyadc3cy7ulwaf2o@treble> From: Tetsuo Handa Message-ID: <19297e6e-c9f7-cd19-d6ac-39ed45d5d269@i-love.sakura.ne.jp> Date: Wed, 11 Jul 2018 06:08:19 +0900 User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.9.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2018/07/11 1:51, David Laight wrote: > From: Josh Poimboeuf >> Sent: 09 July 2018 20:12 >> On Mon, Jul 09, 2018 at 10:49:53AM +0200, Peter Zijlstra wrote: >>> On Sat, Jul 07, 2018 at 10:54:28PM +0900, Tetsuo Handa wrote: >>>>>> Since syzbot is confused by concurrent printk() messages [1], >>>>>> this patch changes show_opcodes() to use snprintf(). >>> >>> But how big of a problem is that really? We can't very well remove all >>> pr_cont stuff from the kernel. >> >> I'd say we should try to make oopses as legible as possible. > > To make oopses legible you need to lock the output between output lines. > Which would require a 'KERN_CONTINUED' marker on the previous print. There is an attempt to prefix context identifier to each line of output ( https://groups.google.com/d/msg/syzkaller/ttZehjXiHTU/JR67pXz3BAAJ ). Therefore, I expect oops messages can stop using pr_cont()/KERN_CONT.