linux-kernel - Re: [PATCH printk v5 1/1] printk: extend console

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Date:   Fri, 6 May 2022 10:16:13 +0200
From:   Petr Mladek <pmladek@...e.com>
To:     Marek Szyprowski <m.szyprowski@...sung.com>
Cc:     John Ogness <john.ogness@...utronix.de>,
        Sergey Senozhatsky <senozhatsky@...omium.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-amlogic@...ts.infradead.org
Subject: Re: [PATCH printk v5 1/1] printk: extend console_lock for
 per-console locking

On Fri 2022-05-06 08:43:02, Marek Szyprowski wrote:
> Hi John,
> 
> On 06.05.2022 00:33, John Ogness wrote:
> > On 2022-05-05, John Ogness <john.ogness@...utronix.de> wrote:
> >> I will go through and check if all access to AML_UART_CONTROL is
> >> protected by port->lock.
> > The startup() callback of the uart_ops is not called with the port
> > locked. I'm having difficulties identifying if the startup() callback
> > can occur after the console was already registered via meson_uart_init()
> > and could be actively printing, but I see other serial drivers are
> > protecting their registers in the startup() callback with the
> > port->lock.

I guess that it is used by the early console before the racy
code is called.

> > Could you try booting the meson hardware with the following change? (And
> > removing any previous debug changes I posted?)
> 
> Bingo! It looks that the startup() is called when getty initializes 
> console. This fixed the issues observed on the Amlogic Meson based boards.
> 
> Feel free to add:
> 
> Tested-by: Marek Szyprowski <m.szyprowski@...sung.com>

Uff, it is a huge relief that it has got fixed.

Best Regards,
Petr