linux-kernel - Re: [PATCH 1/1] boot: Put initcall_debug into its own Kconfig option DEBUG

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Message-ID: <50296CA8.1060303@xenotime.net>
Date:	Mon, 13 Aug 2012 14:07:52 -0700
From:	Randy Dunlap <rdunlap@...otime.net>
To:	Thai Bui <blquythai@...il.com>
CC:	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] boot: Put initcall_debug into its own Kconfig option
 DEBUG_INITCALL

On 08/13/2012 01:57 PM, Thai Bui wrote:

> Putting DEBUG_INITCALL config option to compile out the command-line option
> "initcall_debug".

The patch description does not tell us Why.

presumably to save some memory?

How much memory is saved by disabling DEBUG_INITCALL?


> Signed-off-by: Thai Bui <blquythai@...il.com>
> Reviewed-by: Josh Triplett <josh@...htriplett.org>
> ---
>  Documentation/kernel-parameters.txt |    3 ++-
>  include/linux/init.h                |    4 ++++
>  init/main.c                         |    2 ++
>  lib/Kconfig.debug                   |    9 +++++++++
>  4 files changed, 17 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
> index d99fd9c..3dbaf15 100644
> --- a/Documentation/kernel-parameters.txt
> +++ b/Documentation/kernel-parameters.txt
> @@ -1026,7 +1026,8 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
>  
>  	initcall_debug	[KNL] Trace initcalls as they are executed.  Useful
>  			for working out where the kernel is dying during
> -			startup.
> +			startup. DEBUG_INITCALL needs to be enabled in order
> +			for this option to work.
>  
>  	initrd=		[BOOT] Specify the location of the initial ramdisk
>  
> diff --git a/include/linux/init.h b/include/linux/init.h
> index 6b95109..d2f31f1 100644
> --- a/include/linux/init.h
> +++ b/include/linux/init.h
> @@ -157,7 +157,11 @@ void prepare_namespace(void);
>  
>  extern void (*late_time_init)(void);
>  
> +#ifdef CONFIG_DEBUG_INITCALL
>  extern bool initcall_debug;
> +#else
> +static const bool initcall_debug = false;
> +#endif /* CONFIG_DEBUG_INITCALL */
>  
>  #endif
>    
> diff --git a/init/main.c b/init/main.c
> index ff49a6d..65837f7 100644
> --- a/init/main.c
> +++ b/init/main.c
> @@ -648,8 +648,10 @@ static void __init do_ctors(void)
>  #endif
>  }
>  
> +#ifdef CONFIG_DEBUG_INITCALL
>  bool initcall_debug;
>  core_param(initcall_debug, initcall_debug, bool, 0644);
> +#endif /* CONFIG_DEBUG_INITCALL */
>  
>  static char msgbuf[64];
>  
> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index 8745ac7..424ac93 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -769,6 +769,15 @@ config DEBUG_WRITECOUNT
>  
>  	  If unsure, say N.
>  
> +config DEBUG_INITCALL
> +	bool "Debug initcalls as they are executed"
> +	depends on DEBUG_KERNEL
> +	help
> +	  Enable this for tracing initcalls during startup. Useful for working
> +	  out where the kernel is dying during startup.
> +
> +	  If unsure, say N
> +
>  config DEBUG_MEMORY_INIT
>  	bool "Debug memory initialisation" if EXPERT
>  	default !EXPERT



-- 
~Randy
--
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