linux-kernel - Re: [ANNOUNCE] v5.0.3-rt1

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Date:   Tue, 26 Mar 2019 17:04:04 +0100
From:   John Ogness <john.ogness@...utronix.de>
To:     Julien Grall <julien.grall@....com>
Cc:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-rt-users <linux-rt-users@...r.kernel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Dave P Martin <Dave.Martin@....com>
Subject: Re: [ANNOUNCE] v5.0.3-rt1

Hi Julien,

On 2019-03-26, Julien Grall <julien.grall@....com> 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.

I will setup some tests using systemd on 4.19 and 5.0 to see if I can
see what is going on. It seems there may be some synchronization missing
between the printk kernel thread and /dev/console.

John Ogness