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 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 67793C43381 for ; Wed, 6 Mar 2019 22:23:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3BA85206DD for ; Wed, 6 Mar 2019 22:23:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726761AbfCFWXM (ORCPT ); Wed, 6 Mar 2019 17:23:12 -0500 Received: from Galois.linutronix.de ([146.0.238.70]:52560 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726293AbfCFWXL (ORCPT ); Wed, 6 Mar 2019 17:23:11 -0500 Received: from localhost ([127.0.0.1] helo=vostro.local) by Galois.linutronix.de with esmtp (Exim 4.80) (envelope-from ) id 1h1ewI-0006kr-4y; Wed, 06 Mar 2019 23:23:02 +0100 From: John Ogness To: Petr Mladek Cc: Sergey Senozhatsky , linux-kernel@vger.kernel.org, Peter Zijlstra , Steven Rostedt , Daniel Wang , Andrew Morton , Linus Torvalds , Greg Kroah-Hartman , Alan Cox , Jiri Slaby , Peter Feiner , linux-serial@vger.kernel.org, Sergey Senozhatsky Subject: Re: [RFC PATCH v1 08/25] printk: add ring buffer and kthread References: <20190212143003.48446-1-john.ogness@linutronix.de> <20190212143003.48446-9-john.ogness@linutronix.de> <20190304073856.GA552@jagdpanzerIV> <20190304100044.GC21004@jagdpanzerIV> <20190304110703.GA960@tigerII.localdomain> <87o96p9gtx.fsf@linutronix.de> <20190306155701.wc22i2no5swdcids@pathway.suse.cz> <87r2bjbt47.fsf@linutronix.de> Date: Wed, 06 Mar 2019 23:22:57 +0100 In-Reply-To: <87r2bjbt47.fsf@linutronix.de> (John Ogness's message of "Wed, 06 Mar 2019 22:17:12 +0100") Message-ID: <87k1hbbq2m.fsf@linutronix.de> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/23.4 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2019-03-06, Petr Mladek wrote: >> _Both_ categories are important for the user, but their requirements >> are different: >> >> informational: non-disturbing >> emergency: reliable > > Isn't this already handled by the console_level? > > The informational messages can be reliably read via syslog, /dev/kmsg. > They are related to the normal works when the system works well. > > The emergency messages (errors, warnings) are printed in emergency > situations. They are printed as reliably as possible to the console > because the userspace might not be reliable enough. I've never viewed console_level this way. _If_ console_level really is supposed to define the emergency/informational boundary, all informational messages are supposed to be handled by userspace, and console printing's main objective is reliability... then I would change my proposal such that: - if a console supports write_atomic(), _all_ console printing for that console would use write_atomic() - only consoles without write_atomic() will be printing via the printk-kthread(s) IMO, for consoles with write_atomic(), this would increase reliability over the current mainline implementation. It would also simplify write_atomic() implementations because they would no longer need to synchronize against write(). For those consoles that cannot implement write_atomic() (vt and netconsole come to mind), or as a transition period until remaining console drivers have implemented write_atomic(), these would use the "fallback" of printing fully preemptively in their own kthread using write(). Does this better align with the concept of the console_loglevel and the purpose of console printing? John Ogness