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From:   John Ogness <john.ogness@linutronix.de>
To:     Julien Grall <julien.grall@arm.com>
Cc:     Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
        Thomas Gleixner <tglx@linutronix.de>,
        LKML <linux-kernel@vger.kernel.org>,
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        Dave P Martin <Dave.Martin@arm.com>
Subject: Re: [ANNOUNCE] v5.0.3-rt1
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>
        <28ab7caf-1ada-1c39-c2f9-cd69b2376ef8@arm.com>
Date:   Tue, 26 Mar 2019 17:04:04 +0100
In-Reply-To: <28ab7caf-1ada-1c39-c2f9-cd69b2376ef8@arm.com> (Julien Grall's
        message of "Tue, 26 Mar 2019 10:26:31 +0000")
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Hi Julien,

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