linux-kernel - Re: [PATCH] tracing: add trace console

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Message-ID: <1321463145.4181.30.camel@frodo>
Date:	Wed, 16 Nov 2011 12:05:45 -0500
From:	Steven Rostedt <srostedt@...hat.com>
To:	Johannes Berg <johannes@...solutions.net>
Cc:	Christoph Hellwig <hch@...radead.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...hat.com>
Subject: Re: [PATCH] tracing: add trace console

On Wed, 2011-11-16 at 12:00 -0500, Steven Rostedt wrote:

> diff --git a/kernel/printk.c b/kernel/printk.c
> index 1455a0d..4b8445a 100644
> --- a/kernel/printk.c
> +++ b/kernel/printk.c
> @@ -542,6 +542,7 @@ MODULE_PARM_DESC(ignore_loglevel, "ignore loglevel setting, to"
>  static void _call_console_drivers(unsigned start,
>  				unsigned end, int msg_log_level)
>  {
> +	trace_console(&LOG_BUF(start), end - start);

And since we don't want to trace when end == start, we can use
TRACE_EVENT_CONDITION() and have cond be: len > 0. (where len is the
parameter that takes the end - start.)

This will keep the branch to test len > 0 inside the tracepoint, and it
wont affect the logic when tracing is disabled.

-- Steve


>  	if ((msg_log_level < console_loglevel || ignore_loglevel) &&
>  			console_drivers && start != end) {
>  		if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) {
> 



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