linux-kernel - Re: [PATCH] tracing: annotate emit_log

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Message-ID: <20090528141648.GA6018@nowhere>
Date:	Thu, 28 May 2009 16:16:50 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [PATCH] tracing: annotate emit_log_char() notrace

On Wed, May 27, 2009 at 05:00:44PM +0200, Thomas Gleixner wrote:
> printk calls emit_log_char() in a loop which is cluttering the trace
> buffer. Make it notrace.
> 
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> ---


Does it produce that much annoying traces?
I mean, printk() are usually rare events.

Do you have a particular debugging workflow that makes this
function invasive in the trace?

May be it's because you are debugging using ftrace and other
debugging options that use a lot of printk()
In such case, it would indeed be good to apply this patch.

Thanks,
Frederic.



>  kernel/printk.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> Index: linux-2.6-tip/kernel/printk.c
> ===================================================================
> --- linux-2.6-tip.orig/kernel/printk.c
> +++ linux-2.6-tip/kernel/printk.c
> @@ -499,7 +499,7 @@ static void call_console_drivers(unsigne
>  	_call_console_drivers(start_print, end, msg_level);
>  }
>  
> -static void emit_log_char(char c)
> +static void notrace emit_log_char(char c)
>  {
>  	LOG_BUF(log_end) = c;
>  	log_end++;

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