linux-kernel - Re: [PATCH] let WARN_ON() output the condition

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Message-Id: <20061205172737.14ecfeb3.akpm@osdl.org>
Date:	Tue, 5 Dec 2006 17:27:37 -0800
From:	Andrew Morton <akpm@...l.org>
To:	Jiri Kosina <jkosina@...e.cz>
Cc:	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] let WARN_ON() output the condition

On Wed, 6 Dec 2006 01:51:01 +0100 (CET)
Jiri Kosina <jkosina@...e.cz> wrote:

> [PATCH] let WARN_ON() output the condition
> 
> It is possible, in some cases, that the output of WARN_ON() is ambiguous 
> and can't be properly used to identify the exact condition which caused 
> the warning to trigger. This happens whenever there is a macro that 
> contains multiple WARN_ONs inside. Notable example is spin_lock_mutex(). 
> If any of the two WARN_ONs trigger, we are not able to say which one was 
> the cause (as we get only line number, which however belongs to the place 
> where the macro was expanded).
> 
> This patch lets WARN_ON() to output also the condition and fixes the 
> DEBUG_LOCKS_WARN_ON() macro to pass the condition properly to WARN_ON. The 
> possible drawback could be when someone passes a condition which has 
> sideeffects. Then it would be evaluated twice, instead of current one 
> evaluation. On the other hand, when anyone passes expression with 
> sideeffects to WARN_ON(), he is asking for problems anyway.
> 
> Patch against 2.6.19-rc6-mm2.
> 
> Signed-off-by: Jiri Kosina <jkosina@...e.cz>
> 
> --- 
> 
>  include/asm-generic/bug.h   |    4 ++--
>  include/linux/debug_locks.h |    2 +-
>  2 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/include/asm-generic/bug.h b/include/asm-generic/bug.h
> index a06eecd..af7574e 100644
> --- a/include/asm-generic/bug.h
> +++ b/include/asm-generic/bug.h
> @@ -35,8 +35,8 @@ #ifndef HAVE_ARCH_WARN_ON
>  #define WARN_ON(condition) ({						\
>  	typeof(condition) __ret_warn_on = (condition);			\
>  	if (unlikely(__ret_warn_on)) {					\
> -		printk("WARNING at %s:%d %s()\n", __FILE__,	\
> -			__LINE__, __FUNCTION__);			\
> +		printk("WARNING (%s) at %s:%d %s()\n", #condition,	\
> +			__FILE__,__LINE__, __FUNCTION__);		\
>  		dump_stack();						\
>  	}								\
>  	unlikely(__ret_warn_on);					\
> diff --git a/include/linux/debug_locks.h b/include/linux/debug_locks.h
> index 952bee7..1c2b682 100644
> --- a/include/linux/debug_locks.h
> +++ b/include/linux/debug_locks.h
> @@ -25,7 +25,7 @@ ({									\
>  									\
>  	if (unlikely(c)) {						\
>  		if (debug_locks_off())					\
> -			WARN_ON(1);					\
> +			WARN_ON(c);					\
>  		__ret = 1;						\
>  	}								\
>  	__ret;								\

Give me an additional 5k of text with distro config.  Is it worth it?

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