linux-kernel - Re: [PATCH printk v3 6/6] printk: introduce console_prepend

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Message-ID: <87o7rfd96w.fsf@jogness.linutronix.de>
Date:   Tue, 03 Jan 2023 14:50:23 +0106
From:   John Ogness <john.ogness@...utronix.de>
To:     Petr Mladek <pmladek@...e.com>
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 v3 6/6] printk: introduce
 console_prepend_dropped() for dropped messages

On 2023-01-03, Petr Mladek <pmladek@...e.com> wrote:
> Well, what about making sure that something more useful is always
> printed. For example:
>
> 	/*
> 	 * Make sure outbuf is sufficiently large before prepending.
> 	 * Keep at least the prefix when the message has to be truncated.
> 	 * It is a rather theoretical problem when someone tries to
> 	 * use a minimalist buffer.
> 	 */
> 	if (WARN_ON_ONCE(len + PREFIX_MAX + 1 >= outbuf_sz))
> 		return;

I am fine with this. We won't see this warning anyway. Few lines would
ever be printed correctly if anyone ever tries to use a buffer so small.

> If we want to use this way. It would probably make sense to
> rename PREFIX_MAX to CONSOLE_PREFIX_MAX.

Actually, I would like to rename all of those limit macros to something
that makes more sense for the new code base:

CONSOLE_EXT_LOG_MAX -> CONSOLE_MESSAGE_MAX

CONSOLE_LOG_MAX     -> SYSLOG_MESSAGE_MAX

LOG_LINE_MAX        -> PRINTK_RECORD_MAX

PREFIX_MAX          -> CONSOLE_PREFIX_MAX

I have a patch to do this ready, but I did not want to post it until we
are finished with the thread/atomic work.

John