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,URIBL_BLOCKED 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 C730FC43381 for ; Tue, 26 Mar 2019 10:26:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9FE1120857 for ; Tue, 26 Mar 2019 10:26:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731324AbfCZK0g (ORCPT ); Tue, 26 Mar 2019 06:26:36 -0400 Received: from foss.arm.com ([217.140.101.70]:34026 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726111AbfCZK0f (ORCPT ); Tue, 26 Mar 2019 06:26:35 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 27BD11596; Tue, 26 Mar 2019 03:26:35 -0700 (PDT) Received: from [10.37.9.236] (unknown [10.37.9.236]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 6B1613F614; Tue, 26 Mar 2019 03:26:33 -0700 (PDT) Subject: Re: [ANNOUNCE] v5.0.3-rt1 To: John Ogness Cc: Sebastian Andrzej Siewior , Thomas Gleixner , LKML , linux-rt-users , Steven Rostedt , Dave P Martin References: <20190320171511.icjhdlulgal2yeho@linutronix.de> <791056c4-3575-0bd8-031e-44d0e3b21e54@arm.com> <87tvfrs76z.fsf@linutronix.de> <3cb3c190-e804-982a-1c5b-8545a97379b9@arm.com> <87imw7qm2p.fsf@linutronix.de> From: Julien Grall Message-ID: <28ab7caf-1ada-1c39-c2f9-cd69b2376ef8@arm.com> Date: Tue, 26 Mar 2019 10:26:31 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.5.1 MIME-Version: 1.0 In-Reply-To: <87imw7qm2p.fsf@linutronix.de> Content-Type: text/plain; charset=utf-8; format=flowed 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 Hi John, On 3/25/19 10:34 AM, John Ogness wrote: > On 2019-03-25, Julien Grall wrote: >> [...] >> [ 1.169151] 002: Serial: AMBA PL011 UART driver >> [ 1.254891] 002: 7ff80000.uart: ttyAMA0 at MMIO 0x7ff80000 (irq = 32, base_baud = 0) is a PL011 rev3 >> [ 1.255007] 002: printk: console [ttyAMA0] enabled > > The ttyAMA drivers do not have support for atomic printing, so it is not > the new atomic feature that is causing the mangling. For your setup, all > printk console printing is being handled within a specific context, the > printk kernel thread. This series is somehow making worst when using ttyAMA0. I haven't see any mangling with 4.19-rt. > > It looks to me like some userspace application (systemd?) is writing > directly to /dev/ttyAMA0. If the kernel is also writing to this device > (because it is setup as a console), then the output will be > mangled. There is no high-level synchronization between console output > and directly writing to UART devices. Maybe you need to set your > loglevel so that the kernel does not do the printing? For example, > loglevel=1? I am a bit confused with your suggestion. This would basically means I would not be able to see kernel warning. So this would impair any development on Linux-rt. > > You should see this problem with older kernel versions as well. I have tried with 4.19-rt and didn't see a similar issue. The trace comes pretty clean in one go. With 5.0-rt, the trace never come clean. Cheers, -- Julien Grall