linux-kernel - Re: [PATCH 06/11] ftrace: add ftrace warn on to disable ftrace

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Date:	Wed, 22 Oct 2008 12:12:57 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	linux-kernel@...r.kernel.org, mingo@...e.hu, fweisbec@...il.com,
	sagar.abhishek@...il.com, davem@...emloft.net, tglx@...utronix.de,
	peterz@...radead.org, torvalds@...ux-foundation.org,
	srostedt@...hat.com
Subject: Re: [PATCH 06/11] ftrace: add ftrace warn on to disable ftrace

On Wed, 22 Oct 2008 14:43:19 -0400
Steven Rostedt <rostedt@...dmis.org> wrote:

> Add ftrace warn on to disable ftrace as well as report a warning.
> 
> Signed-off-by: Steven Rostedt <srostedt@...hat.com>
> ---
>  kernel/trace/ftrace.c |   29 ++++++++++++++++++++++-------
>  1 file changed, 22 insertions(+), 7 deletions(-)
> 
> Index: linux-compile.git/kernel/trace/ftrace.c
> ===================================================================
> --- linux-compile.git.orig/kernel/trace/ftrace.c	2008-10-22 13:17:29.000000000 -0400
> +++ linux-compile.git/kernel/trace/ftrace.c	2008-10-22 13:20:11.000000000 -0400
> @@ -32,6 +32,24 @@
>  
>  #include "trace.h"
>  
> +#define FTRACE_WARN_ON(cond)			\
> +	do {					\
> +		if (unlikely(cond)) {		\
> +			WARN_ON(1);		\
> +			ftrace_kill();		\
> +		}				\
> +	} while (0)

This could be coded as

	if (WARN_ON(cond))
		ftrace_kill();

> +#define FTRACE_WARN_ON_ONCE(cond)		\
> +	do {					\
> +		static int once;		\
> +		if (unlikely(cond) && !once) {	\
> +			once++;			\
> +			WARN_ON(1);		\
> +			ftrace_kill();		\
> +		}				\
> +	} while (0)


	if (WARN_ON_ONCE(cond))
		ftrace_kill();


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