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 A9E0CC433F5 for ; Fri, 25 Feb 2022 10:11:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239336AbiBYKMW convert rfc822-to-8bit (ORCPT ); Fri, 25 Feb 2022 05:12:22 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50008 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230206AbiBYKMU (ORCPT ); Fri, 25 Feb 2022 05:12:20 -0500 Received: from eu-smtp-delivery-151.mimecast.com (eu-smtp-delivery-151.mimecast.com [185.58.86.151]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 0615622520 for ; Fri, 25 Feb 2022 02:11:47 -0800 (PST) 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-25-PJYvd1KwMOGbmBnNbq1ouw-1; Fri, 25 Feb 2022 10:11:45 +0000 X-MC-Unique: PJYvd1KwMOGbmBnNbq1ouw-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 15.0.1497.28; Fri, 25 Feb 2022 10:11:43 +0000 Received: from AcuMS.Aculab.com ([fe80::994c:f5c2:35d6:9b65]) by AcuMS.aculab.com ([fe80::994c:f5c2:35d6:9b65%12]) with mapi id 15.00.1497.028; Fri, 25 Feb 2022 10:11:43 +0000 From: David Laight To: 'Willy Tarreau' CC: 'Steven Rostedt' , LKML , Petr Mladek , "Sergey Senozhatsky" , John Ogness Subject: RE: Strange output on the console Thread-Topic: Strange output on the console Thread-Index: AQHYKfxF0QTTTto/+k+8VsyEcwRQo6yjyM1ggAAHToCAADtxAA== Date: Fri, 25 Feb 2022 10:11:43 +0000 Message-ID: <1dcb185901f04a5ea2476a449e371167@AcuMS.aculab.com> References: <20220224230035.36547137@gandalf.local.home> <61226fc12ff9459d8daed8e346d6ab94@AcuMS.aculab.com> <20220225063637.GA18039@1wt.eu> In-Reply-To: <20220225063637.GA18039@1wt.eu> 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: Willy Tarreau > Sent: 25 February 2022 06:37 > > On Fri, Feb 25, 2022 at 06:12:35AM +0000, David Laight wrote: > > From: Steven Rostedt > > > Sent: 25 February 2022 04:01 > > > > > > I've been noticing that my tests have been spitting out strange output on > > > the console. It would happen at boot up and then clear up. It looks like > > > something screwed up with the serial timing. > > > > > > Attached is a dmesg of one of my test runs as an example. > > > > > > I've noticed this on both 32 bit and 64 bit x86. > > > > > > I haven't had time to look deeper into this, but I figured I let you know > > > about it. > > > > > > And it always seems to happen right after: > > > > > > Serial: 8250/16550 driver, 4 ports, IRQ sharing enabled > > > > > > Maybe this is a serial issue and not a printk one? :-/ > > > > Looks very much like the serial baud rate is being reset. > > I don't think it's the baud rate, characters are still readable, it > looks more like a fifo being too short and causing lots of chars to > be dropped. Just before it recovers there is this output: ATaitoscic nitahi tuPiet mfba Ae: aD nCt AH0 nP0 That is probably 'fifo not enabled'. But the earlier output doesn't have many different characters in it. Which is typical of the baud rate being wrong. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)