linux-kernel - Re: [PATCH v2 2/2] printk: Add printk.console

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Message-ID: <YQPb4LGzj+NuZ7qL@alley>
Date:   Fri, 30 Jul 2021 13:00:48 +0200
From:   Petr Mladek <pmladek@...e.com>
To:     Dmitry Safonov <dima@...sta.com>
Cc:     linux-kernel@...r.kernel.org,
        Dmitry Safonov <0x7f454c46@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        John Ogness <john.ogness@...utronix.de>,
        Sergey Senozhatsky <senozhatsky@...omium.org>,
        Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [PATCH v2 2/2] printk: Add printk.console_verbose boot parameter

On Tue 2021-07-13 02:15:11, Dmitry Safonov wrote:
> console_verbose() increases console loglevel to CONSOLE_LOGLEVEL_MOTORMOUTH,
> which provides more information to debug a panic/oops.
> 
> Unfortunately, in Arista we maintain some DUTs (Device Under Test) that
> are configured to have 9600 baud rate. While verbose console messages
> have their value to post-analyze crashes, on such setup they:
> - may prevent panic/oops messages being printed
> - take too long to flush on console resulting in watchdog reboot
> 
> In all our setups we use kdump which saves dmesg buffer after panic,
> so in reality those extra messages on console provide no additional value,
> but rather add risk of not getting to __crash_kexec().
> 
> Provide printk.console_verbose boot parameter, which allows to switch off
> printk being verbose on oops/panic/lockdep (making it boot parameter
> instead of compile-option suggested-by Petr).
> 
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: John Ogness <john.ogness@...utronix.de>
> Cc: Petr Mladek <pmladek@...e.com>
> Cc: Sergey Senozhatsky <senozhatsky@...omium.org>
> Cc: Steven Rostedt <rostedt@...dmis.org>
> Signed-off-by: Dmitry Safonov <dima@...sta.com>

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

Best Regards,
Petr