linux-kernel - Re: [PATCH 2/3] tracing: Use pr_crit() instead of long fancy messages

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Date:   Thu, 1 Apr 2021 11:14:47 +0200
From:   Petr Mladek <pmladek@...e.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Geert Uytterhoeven <geert+renesas@...der.be>,
        Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
        Ingo Molnar <mingo@...hat.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        John Ogness <john.ogness@...utronix.de>,
        Gary R Hook <gary.hook@....com>,
        Marco Elver <elver@...gle.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        linux-embedded@...r.kernel.org
Subject: Re: [PATCH 2/3] tracing: Use pr_crit() instead of long fancy messages

On Wed 2021-03-31 09:40:07, Steven Rostedt wrote:
> On Wed, 31 Mar 2021 11:31:03 +0200
> Geert Uytterhoeven <geert+renesas@...der.be> wrote:
> 
> > This reduces kernel size by ca. 0.5 KiB.
> 
> If you are worried about size, disable tracing and it will go away
> entirely. 0.5KiB is a drop in the bucket compared to what tracing adds in
> size overhead.
> 
> Sorry, but NAK.
> 
> This has been very successful in stopping people from adding trace_printk()
> to the kernel, and I like to keep it that way.

I agree with Steven. I believe that the eye-catching form is
important.

Anyway, all three patches are replacing text that have
many common parts. It is:

	pr_warn("\n");
	pr_warn("**********************************************************\n");
	pr_warn("**   NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE   **\n");
	pr_warn("**                                                      **\n");
	pr_warn("** <Something is enabled/used.>			 **\n");
	pr_warn("**                                                      **\n");
	pr_warn("** <Description of the effect and why it should not     **\n");
	pr_warn("** happen on production kernel>			**\n");
	pr_warn("**                                                      **\n");
	pr_warn("** If you see this message and you are not debugging    **\n");
	pr_warn("** the kernel, report this immediately to your vendor!  **\n");
	pr_warn("**                                                      **\n");
	pr_warn("**   NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE   **\n");
	pr_warn("**********************************************************\n");

It might be useful to avoid cut&pasting this entire blob and unify the
common parts.

My only concern is how to define the caller-specific lines so that
they fit with the common ones. They should not be longer than the
header and footer. We need to find a good compromise between
usability and over-engineering.

Also we have to keep bikeshading under control ;-)

Best Regards,
Petr