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Date:   Wed, 24 Jun 2020 12:04:08 -0400
From:   Steven Rostedt <rostedt@goodmis.org>
To:     Nicolas Boichat <drinkcat@chromium.org>
Cc:     linux-kernel@vger.kernel.org, Ingo Molnar <mingo@redhat.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Kees Cook <keescook@chromium.org>,
        Jason Gunthorpe <jgg@ziepe.ca>,
        Daniel Vetter <daniel.vetter@ffwll.ch>,
        Peter Zijlstra <peterz@infradead.org>,
        Vinod Koul <vkoul@kernel.org>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Alexey Dobriyan <adobriyan@gmail.com>,
        Tiezhu Yang <yangtiezhu@loongson.cn>,
        Thomas Gleixner <tglx@linutronix.de>,
        "Guilherme G . Piccoli" <gpiccoli@canonical.com>,
        Will Deacon <will@kernel.org>, dianders@chromium.org,
        groeck@chromium.org
Subject: Re: [PATCH] kernel/trace: Add TRACING_ALLOW_PRINTK config option
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On Wed, 24 Jun 2020 16:45:24 +0800
Nicolas Boichat <drinkcat@chromium.org> wrote:

> trace_printk is only meant as a debugging tool, and should never be
> compiled into production code without source code changes, as
> indicated by the warning that shows up on boot if any trace_printk
> is called:
>  **   NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE   **
>  **                                                      **
>  ** trace_printk() being used. Allocating extra memory.  **
>  **                                                      **
>  ** This means that this is a DEBUG kernel and it is     **
>  ** unsafe for production use.                           **
> 
> If this option is set to n, the kernel will generate a build-time
> error if trace_printk is used.
> 
> Signed-off-by: Nicolas Boichat <drinkcat@chromium.org>

Interesting. Note, this will prevent modules with trace_printk from
being loaded as well.

-- Steve