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 49320C282C2 for ; Wed, 13 Feb 2019 16:53:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 20FA1222D0 for ; Wed, 13 Feb 2019 16:53:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2392793AbfBMQxg convert rfc822-to-8bit (ORCPT ); Wed, 13 Feb 2019 11:53:36 -0500 Received: from eu-smtp-delivery-151.mimecast.com ([146.101.78.151]:24852 "EHLO eu-smtp-delivery-151.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2392559AbfBMQxg (ORCPT ); Wed, 13 Feb 2019 11:53:36 -0500 Received: from AcuMS.aculab.com (156.67.243.126 [156.67.243.126]) (Using TLS) by relay.mimecast.com with ESMTP id uk-mta-131-5bfnswKhP721ybj2SXPzFA-1; Wed, 13 Feb 2019 16:53:32 +0000 Received: from AcuMS.Aculab.com (fd9f:af1c:a25b::d117) by AcuMS.aculab.com (fd9f:af1c:a25b::d117) with Microsoft SMTP Server (TLS) id 15.0.1347.2; Wed, 13 Feb 2019 16:54:15 +0000 Received: from AcuMS.Aculab.com ([fe80::43c:695e:880f:8750]) by AcuMS.aculab.com ([fe80::43c:695e:880f:8750%12]) with mapi id 15.00.1347.000; Wed, 13 Feb 2019 16:54:15 +0000 From: David Laight To: 'John Ogness' , "linux-kernel@vger.kernel.org" CC: Peter Zijlstra , Petr Mladek , Sergey Senozhatsky , 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 00/25] printk: new implementation Thread-Topic: [RFC PATCH v1 00/25] printk: new implementation Thread-Index: AQHUwt+yw0tokMnSLkaf/+oK4gykJqXd8fOw Date: Wed, 13 Feb 2019 16:54:15 +0000 Message-ID: <6f965383270d45d6ac26529fec5ad470@AcuMS.aculab.com> References: <20190212143003.48446-1-john.ogness@linutronix.de> In-Reply-To: <20190212143003.48446-1-john.ogness@linutronix.de> Accept-Language: en-GB, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.107] MIME-Version: 1.0 X-MC-Unique: 5bfnswKhP721ybj2SXPzFA-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: John Ogness > Sent: 12 February 2019 14:30 ... > - A dedicated kernel thread is created for printing to all consoles in > a fully preemptible context. > > - A new (optional) console operation "write_atomic" is introduced that > console drivers may implement. This function must be NMI-safe. An > implementation for the 8250 UART driver is provided. > > - The concept of "emergency messages" is introduced that allows > important messages (based on a new emergency loglevel threshold) to > be immediately written to any consoles supporting write_atomic, > regardless of the context. ... Does this address my usual 'gripe' that the output is written to the console by syslogd and not by the kernel itself? When you are trying to find out where the system is completely deadlocking you need the 'old fashioned' completely synchronous kernel printf(). David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)