linux-kernel - Re: [PATCH printk v4 05/39] printk: fix setting first seq for consoles

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Date:   Tue, 15 Nov 2022 13:04:07 +0100
From:   Petr Mladek <pmladek@...e.com>
To:     John Ogness <john.ogness@...utronix.de>
Cc:     Sergey Senozhatsky <senozhatsky@...omium.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH printk v4 05/39] printk: fix setting first seq for
 consoles

On Mon 2022-11-14 17:34:58, John Ogness wrote:
> It used to be that all consoles were synchronized with respect to
> which message they were printing. After commit a699449bb13b ("printk:
> refactor and rework printing logic"), all consoles have their own
> @seq for tracking which message they are on. That commit also changed
> how the initial sequence number was chosen. Instead of choosing the
> next non-printed message, it chose the sequence number of the next
> message that will be added to the ringbuffer.
> 
> That change created a possibility that a non-boot console taking over
> for a boot console might skip messages if the boot console was behind
> and did not have a chance to catch up before being unregistered.
> 
> Since it is not possible to know which boot console a console is
> taking over, use the lowest @seq of all the enabled boot consoles. If
> no boot consoles are available/enabled, begin with the next message
> that will be added to the ringbuffer.
> 
> Also, since boot consoles are meant to be used at boot time, handle
> them the same as CON_PRINTBUFFER to ensure that no initial messages
> are skipped.
> 
> Signed-off-by: John Ogness <john.ogness@...utronix.de>

Reviewed-by: Petr Mladek <pmladek@...e.com>

Best Regards,
Petr