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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9C30FC433EF for ; Fri, 17 Jun 2022 15:01:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1382950AbiFQPBm convert rfc822-to-8bit (ORCPT ); Fri, 17 Jun 2022 11:01:42 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34118 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1382627AbiFQPBk (ORCPT ); Fri, 17 Jun 2022 11:01:40 -0400 Received: from eu-smtp-delivery-151.mimecast.com (eu-smtp-delivery-151.mimecast.com [185.58.85.151]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 2A64A3E0E4 for ; Fri, 17 Jun 2022 08:01:39 -0700 (PDT) Received: from AcuMS.aculab.com (156.67.243.121 [156.67.243.121]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384) id uk-mta-56-yIBenb7EPhWdGuPCD_Wigg-1; Fri, 17 Jun 2022 16:01:36 +0100 X-MC-Unique: yIBenb7EPhWdGuPCD_Wigg-1 Received: from AcuMS.Aculab.com (fd9f:af1c:a25b:0:994c:f5c2:35d6:9b65) by AcuMS.aculab.com (fd9f:af1c:a25b:0:994c:f5c2:35d6:9b65) with Microsoft SMTP Server (TLS) id 15.0.1497.36; Fri, 17 Jun 2022 16:01:34 +0100 Received: from AcuMS.Aculab.com ([fe80::994c:f5c2:35d6:9b65]) by AcuMS.aculab.com ([fe80::994c:f5c2:35d6:9b65%12]) with mapi id 15.00.1497.036; Fri, 17 Jun 2022 16:01:34 +0100 From: David Laight To: 'Petr Mladek' , "Jason A. Donenfeld" CC: John Ogness , Marco Elver , "linux-kernel@vger.kernel.org" Subject: RE: 5.19 printk breaks message ordering Thread-Topic: 5.19 printk breaks message ordering Thread-Index: AQHYglWHYY5jQBSQoEy5fw0dudLMr61Tr9rQ Date: Fri, 17 Jun 2022 15:01:33 +0000 Message-ID: References: In-Reply-To: Accept-Language: en-GB, 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 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=C51A453 smtp.mailfrom=david.laight@aculab.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: aculab.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Petr Mladek > Sent: 17 June 2022 15:21 ... > > I assume this is mostly caused by your threaded printk patchset > > Console has never been fully synchronous. printk() did console_trylock() > and flushed the message to the console only the lock was available. > The console kthreads made it asynchronous always when the kthreads > are available and system is in normal state. What priority do these kthreads run at? I'd have thought they ought to run at a high priority? That should tend to give kernel messages priority over user ones. Quite how high is another matter. Probably a bit below the RT/FIFO:50 of threaded ISR. Although if an x86 one ends up doing software scrolling of the vga text buffer using the ISA speed accesses that usually requires maybe not! Maybe that is faster on modern systems - but I doubt it. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)