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SubjectRe: Please revert "debug: Make CONFIG_EXPERT select CONFIG_DEBUG_KERNEL to unhide debug options"
On Mon, Oct 10, 2011 at 09:29:48AM +0200, Ingo Molnar wrote:
> * Adrian Bunk <> wrote:
> I think you are wrong not just about that detail but about the whole
> premise of your complaint as well:
> > - 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.

Then you would have to remove the dependency on EXPERT from the prompt,
and allow unsetting DEBUG_BUGVERBOSE with EXPERT=n, DEBUG_KERNEL=y.

Note that this is completely unrelated to the commit we are discussing,
since commit f505c553 has no effect in the EXPERT=n case you are
discussing here.

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

DEBUG_BUGVERBOSE does not depend on EXPERT.

But EXPERT is currently required for disabling it.

This part of our discussion boils down to the following options:
1. DEBUG_KERNEL allows a user to enable additional debugging
2. DEBUG_KERNEL gives a user full control over all debug options

Traditionally it was 1., to tell a user reporting a bug that he should
enable additional debugging in his kernel - without him accidentally
disabling useful debugging.

Again, this part of the discussion is unrelated to commit f505c553.

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

I don't see the advantage that EXPERT=y is now unconditionally enabling
the DEBUG_KERNEL knob.

When I am an "expert", why can't I still decide myself globally if I
want to enable more debugging or not?

Another problem is that we have code using "#ifdef CONFIG_DEBUG_KERNEL"
so enabling EXPERT for making your kernel smaller can make your kernel
bigger, but such usages should anyway get own config options.

> This is a pretty easy model to think about.

There are many options in the kernel that only enable seeing other
config options.

With that model, shouldn't EXPERT also have
and many other similar select's?

The point I am trying to make here is that there are many convenience
config options that only exist to allow a user to hide a bunch of
options he is not interested in, and DEBUG_KERNEL is one of them. [1]

> > The crazy select added in commit f505c553 is wrong.
> Why? Your original message does not explain it.

It is not needed for what it was claimed it was needed for,
and it is a bad idea in general.

If I didn't explain that properly that was my fault,
I hope the explanation in this email is better.

> Thanks,
> Ingo


[1] ignoring the buggy code using "#ifdef CONFIG_DEBUG_KERNEL"


"Is there not promise of rain?" Ling Tan asked suddenly out
of the darkness. There had been need of rain for many days.
"Only a promise," Lao Er said.
Pearl S. Buck - Dragon Seed

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