linux-kernel - Re: Please revert "debug: Make CONFIG_EXPERT select CONFIG_DEBUG

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Date:	Mon, 10 Oct 2011 09:29:48 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Adrian Bunk <bunk@...sta.de>
Cc:	Josh Triplett <josh@...htriplett.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org,
	Frederic Weisbecker <fweisbec@...il.com>,
	Sam Ravnborg <sam@...nborg.org>
Subject: Re: Please revert "debug: Make CONFIG_EXPERT select
 CONFIG_DEBUG_KERNEL to unhide debug options"

* Adrian Bunk <bunk@...sta.de> wrote:

> On Fri, Sep 30, 2011 at 08:05:19AM -0700, Josh Triplett wrote:
> > On Fri, Sep 30, 2011 at 04:42:45PM +0300, Adrian Bunk wrote:
> >...
> > > Let me point at the obvious fact that both CONFIG_DEBUG_BUGVERBOSE and 
> > > CONFIG_DEBUG_RODATA do depend on DEBUG_KERNEL, and are contrary to the 
> > > claim of the author of this patch never enabled with 
> > > CONFIG_DEBUG_KERNEL=n. [1]
> > 
> > Not true:
> > 
> > ~/src/linux-2.6$ rm .config
> > ~/src/linux-2.6$ make allnoconfig
> >   HOSTCC  scripts/basic/fixdep
> >   HOSTCC  scripts/kconfig/conf.o
> >   HOSTCC  scripts/kconfig/zconf.tab.o
> >   HOSTLD  scripts/kconfig/conf
> > scripts/kconfig/conf --allnoconfig Kconfig
> > #
> > # configuration written to .config
> > #
> > ~/src/linux-2.6$ grep BUGVERBOSE .config
> > CONFIG_DEBUG_BUGVERBOSE=y
> > ~/src/linux-2.6$ grep DEBUG_KERNEL .config
> > # CONFIG_DEBUG_KERNEL is not set
> > 
> > DEBUG_BUGVERBOSE does not depend on DEBUG_KERNEL; it just only shows up
> > with DEBUG_KERNEL (and EXPERT) set.  The *description* has a conditional
> > on DEBUG_KERNEL and EXPERT:
> > 
> > config DEBUG_BUGVERBOSE
> >         bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT
> >...
> 
> Apologies, I was wrong on DEBUG_BUGVERBOSE
> (but for DEBUG_RODATA I was right).

I think you are wrong not just about that detail but about the whole 
premise of your complaint as well:

>  config DEBUG_BUGVERBOSE
> -	bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT
> +	bool "Verbose BUG() reporting (adds 70K)" if EXPERT
> 
> This part of the patch would have been the correct and complete 
> solution for DEBUG_BUGVERBOSE.

Not really - it's a debugging-only option and when i turn on 
CONFIG_DEBUG_KERNEL I expect to have full config control over all 
debug options - with sane defaults provided.

I definitely don't want a debugging option to depend on 
CONFIG_EXPERT.

CONFIG_EXPERT is a superset to all that: it implies config control 
over all debug options *and* over many other kernel components as 
well.

This is a pretty easy model to think about.

> The crazy select added in commit f505c553 is wrong.

Why? Your original message does not explain it.

Thanks,

	Ingo
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