Re: [RFC 1/4] CONFIG_STABLE: Define it

[Chris Snook]

Satyam Sharma wrote:
> On 7/20/07, Chris Snook <csnook@xxxxxxxxxx> wrote:
> > Satyam Sharma wrote:
> > > On 7/20/07, Chris Snook <csnook@xxxxxxxxxx> wrote:
> > >> Satyam Sharma wrote:
> > >> > [ Just cleaning up my inbox, and stumbled across this thread ... ]
> > >> >
> > >> >
> > >> > On 5/31/07, clameter@xxxxxxx <clameter@xxxxxxx> wrote:
> > >> >> Introduce CONFIG_STABLE to control checks only useful for 
> > development.
> > >> >>
> > >> >> Signed-off-by: Christoph Lameter <clameter@xxxxxxx>
> > >> >> [...]
> > >> >>  menu "General setup"
> > >> >>
> > >> >> +config STABLE
> > >> >> +       bool "Stable kernel"
> > >> >> +       help
> > >> >> +         If the kernel is configured to be a stable kernel then
> > >> various
> > >> >> +         checks that are only of interest to kernel development
> > >> will be
> > >> >> +         omitted.
> > >> >> +
> > >> >
> > >> >
> > >> > "A programmer who uses assertions during testing and turns them off
> > >> > during production is like a sailor who wears a life vest while 
> > drilling
> > >> > on shore and takes it off at sea."
> > >> >                                                - Tony Hoare
> > >> >
> > >> >
> > >> > Probably you meant to turn off debug _output_ (and not _checks_)
> > >> > with this config option? But we already have CONFIG_FOO_DEBUG_BAR
> > >> > for those situations ...
> > >>
> > >> There are plenty of validation and debugging features in the kernel
> > >> that go WAY
> > >> beyond mere assertions, often imposing significant overhead
> > >> (particularly when
> > >> you scale up) or creating interfaces you'd never use unless you were
> > >> doing
> > >> kernel development work.  You really do want these features completely
> > >> removed
> > >> from production kernels.
> > >
> > > As for entire such "development/debugging-related features", most (all,
> > > really)
> > > should anyway have their own config options.
> >
> > They do.  With kconfig dependencies, we can ensure that those config 
> > options are
> > off when CONFIG_STABLE is set.  That way you only have to set one 
> > option to
> > ensure that all these expensive checks are disabled.
>
> Oh, so you mean use this (the negation of this, actually) as a universal
> kconfig dependency of all other such development/debugging related stuff?
> Hmm, the name is quite misleading in that case.

There are many different ways you can use it.  If I'm writing a configurable 
feature, I could make it depend on !CONFIG_STABLE, or I could ifdef my code out 
if CONFIG_STABLE is set, unless a more granular option is also set.  The 
maintainer of the code that uses the config option has a lot of flexibility, at 
least until we start enforcing standards.

	-- Chris
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