linux-kernel - Re: Strange output on the console

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Date:   Fri, 25 Feb 2022 07:36:37 +0100
From:   Willy Tarreau <w@....eu>
To:     David Laight <David.Laight@...LAB.COM>
Cc:     "'Steven Rostedt'" <rostedt@...dmis.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <senozhatsky@...omium.org>,
        John Ogness <john.ogness@...utronix.de>
Subject: Re: Strange output on the console

On Fri, Feb 25, 2022 at 06:12:35AM +0000, David Laight wrote:
> From: Steven Rostedt
> > Sent: 25 February 2022 04:01
> > 
> > I've been noticing that my tests have been spitting out strange output on
> > the console. It would happen at boot up and then clear up. It looks like
> > something screwed up with the serial timing.
> > 
> > Attached is a dmesg of one of my test runs as an example.
> > 
> > I've noticed this on both 32 bit and 64 bit x86.
> > 
> > I haven't had time to look deeper into this, but I figured I let you know
> > about it.
> > 
> > And it always seems to happen right after:
> > 
> >   Serial: 8250/16550 driver, 4 ports, IRQ sharing enabled
> > 
> > Maybe this is a serial issue and not a printk one? :-/
> 
> Looks very much like the serial baud rate is being reset.

I don't think it's the baud rate, characters are still readable, it
looks more like a fifo being too short and causing lots of chars to
be dropped.

Willy