config(8) should check if a scheduler is selected

[Scott Long]

Bruce Evans wrote:
> On Fri, 18 Apr 2003, Kris Kennaway wrote:
> 
> 
>>On Fri, Apr 18, 2003 at 04:47:43PM -0400, David Magda wrote:
>>
>>
>>>If you run config(8) on a kernel configuration file which doesn't
>>>have a scheduler selected then it does *NOT* complain.
>>
>>How is this different to any of the other mandatory kernel components
>>or dependencies?  You can build a kernel that will refuse to link in
>>many ways; missing a scheduler is just a new mistake you might make if
>>you forget to read /usr/src/UPDATING.
> 
> 
> It is the only mandatory option (sic).  Kernels with no options (although
> they might not be useful) can be built except for this bug.  Example of
> a minimal config file (before misconfiguration of the configuration of
> scheduling).
> 
> %%%
> machine		i386
> cpu		I686_CPU
> ident		MIN
> %%%
> 

The scheduler is (one of) the first core subsystems to be made
modular.  If by chance the VM system became modular (VM_MACH, VM_UVM =-)
you'd have a similar situation there also.
I'm afraid that the lack of seatbelts in config(8) for SCHED_xxx will
generate a lot of user complaints when 5.1 is released.  Since code to
implement it has not magically appeared yet, we might have to make due
with adding extra eye-catching comments to things like NOTES and
GENERIC.

> BTW, a minimal kernel is now almost 3 times as large as in FreeBSD-2 due
> to general bloat and misconfiguration of configuration in the opposite
> way (subsystems much larger than scheduling are standard; you can still
> leave out FFS and INET but many less useful subsystems are standard).

Some of us remember when 250k FreeBSD kernels were not hard to
configure =-)

Scott