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_HELO_NONE,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 48A7DC04AB6 for ; Tue, 28 May 2019 14:21:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1FCB3206BA for ; Tue, 28 May 2019 14:21:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727606AbfE1OVY (ORCPT ); Tue, 28 May 2019 10:21:24 -0400 Received: from www262.sakura.ne.jp ([202.181.97.72]:58540 "EHLO www262.sakura.ne.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726532AbfE1OVX (ORCPT ); Tue, 28 May 2019 10:21:23 -0400 Received: from fsav103.sakura.ne.jp (fsav103.sakura.ne.jp [27.133.134.230]) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTP id x4SELMwP009072; Tue, 28 May 2019 23:21:22 +0900 (JST) (envelope-from penguin-kernel@i-love.sakura.ne.jp) Received: from www262.sakura.ne.jp (202.181.97.72) by fsav103.sakura.ne.jp (F-Secure/fsigk_smtp/530/fsav103.sakura.ne.jp); Tue, 28 May 2019 23:21:22 +0900 (JST) X-Virus-Status: clean(F-Secure/fsigk_smtp/530/fsav103.sakura.ne.jp) Received: from [192.168.1.8] (softbank126012062002.bbtec.net [126.12.62.2]) (authenticated bits=0) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTPSA id x4SELKgN009063 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NO); Tue, 28 May 2019 23:21:21 +0900 (JST) (envelope-from penguin-kernel@i-love.sakura.ne.jp) Subject: Re: [RFC] printk/sysrq: Don't play with console_loglevel To: Petr Mladek , Sergey Senozhatsky Cc: Dmitry Safonov , linux-kernel@vger.kernel.org, Greg Kroah-Hartman , Jiri Slaby , Sergey Senozhatsky , Steven Rostedt References: <20190528002412.1625-1-dima@arista.com> <20190528041500.GB26865@jagdpanzerIV> <20190528044619.GA3429@jagdpanzerIV> <20190528134227.xyb3622gjwu52q4r@pathway.suse.cz> From: Tetsuo Handa Message-ID: Date: Tue, 28 May 2019 23:21:17 +0900 User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: <20190528134227.xyb3622gjwu52q4r@pathway.suse.cz> 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 2019/05/28 22:42, Petr Mladek wrote: >> Ahh.. OK, now I sort of remember why I gave up on this idea (see [1] >> at the bottom, when it comes to uv_nmi_dump_state()) - printk_NMI and >> printk-safe redirections. >> >> NMI >> loglevel = NEW >> printk -> printk_safe_nmi >> loglevel = OLD >> >> iret >> >> IRQ >> flush printk_safe_nmi -> printk >> // At this point we don't remember about >> // loglevel manipulation anymore >> iret > > printk_safe buffer preserves KERN_* headers. It should be > possible to insert KERN_UNSUPPRESSED there. But is context dependent buffer large enough to hold SysRq-t output? I think that only main logbuf can become large enough to hold SysRq-t output. We can add KERN_UNSUPPRESSED to SysRq's header line. But I don't think that we can automatically add KERN_UNSUPPRESSED to SysRq's body lines based on some context information. If we want to avoid manipulating console_loglevel, we need to think about how to make sure that KERN_UNSUPPRESSED is added to all lines from such context without overflowing capacity of that buffer.