Re: [PATCH 2/2] UML - Fix kernel stack size on x86_64

[Andrew Morton <akpm@linux-foundation.org>]

On Tue, 5 Jun 2007 20:37:52 -0400 Jeff Dike <jdike@addtoit.com> wrote:

> On Tue, Jun 05, 2007 at 05:00:01PM -0700, Andrew Morton wrote:
> > On Tue, 5 Jun 2007 16:50:55 -0400
> > Jeff Dike <jdike@addtoit.com> wrote:
> > 
> > > [ This is 2.6.22 material ]
> > > 
> > > Having KERNEL_STACK_ORDER in defconfig overrides the value provided by
> > > Kconfig, breaking UML/x86_64, which wants 2 page stacks.
> 
> > That means the Kconfig rules are wrong, surely?
> 
> I'm far from a Kconfig expert,

Me either.  I learn enough for the problem at hand, then instaforget it
again.  Kinda like perl.

> but what I have is
> 
> config KERNEL_STACK_ORDER
> 	int "Kernel stack size order"
> 	default 1 if 64BIT
> 	default 0 if !64BIT
> 
> which seems reasonably clear and simple...
> 

hm, OK, there's the problem.  This is an offered-to-the-user config option.

If you do

-	int "Kernel stack size order"
+	int

then this rule will no longer be offered to the user and `make oldconfig'
(actually anythingconfig) will override whatever happens to be in .config
for KERNEL_STACK_ORDER.

I'm not sure if that's actually what you want, but if the current situation
is that a random CONFIG_KERNEL_STACK_ORDER=0 left over in .config will
break the kernel at runtime then I think something sterner than editing
defconfig is needed?