On Sun, Oct 07, 2012 at 04:18:54PM -0400, Dave Jones wrote:
> On Sun, Oct 07, 2012 at 09:30:29AM -0700, Paul E. McKenney wrote:
>
> > > I think Kconfig is mostly what distro would like to use the thing is
> > > the Kconfig text needs to be there upfront when its merged, not two
> > > months later, since then it too late for a distro to notice.
> > >
> > > I'd bet most distros would read the warnings, but in a lot of cases
> > > the warning don't exist until its too late.
> >
> > In the case of CONFIG_RCU_USER_QS you are quite right, the warning
> > should have been there from the beginning and was not. I suppose you
> > could argue that the warning was not sufficiently harsh in the case of
> > CONFIG_RCU_FAST_NO_HZ, but either way it did get ignored:
>
> Maybe if we had a universally agreed upon tag for kconfig, like
> "distro recommendation: N" that would make things obvious, and also allow
> those of us unfortunate enough to maintain distro kernels to have something
> to easily grep for. This would also catch the case when you eventually
> (hopefully)
> flip from an N to a Y.
>
> There will likely still be some distros that will decide they know better
> (and I'm pretty sure eventually I'll find reason to do so myself), but it at
> least
> gives the feature maintainer the "I told you so" clause.
>
> Something we do quite often for our in-development kernels is enable something
> that's shiny, new and unproven, and then when we branch for a release, we turn
> it back off. It would be great if a lot of this kind of thing could be more
> automated.
One approach would be to have CONFIG_DISTRO, so that experimental
features could use "depends on !DISTRO", but also to have multiple
"BLEEDING" symbols. For example, given a CONFIG_DISTRO_BLEEDING_HPC
and CONFIG_DISTRO_BLEEDING_RT, CONFIG_RCU_USER_QS might eventually
use the following clause:
depends on !DISTRO || DISTRO_BLEEDING_HPC || DISTRO_BLEEDING_RT
A normal distro would define DISTRO, a distro looking to provide bleeding-edge
HPC or real-time features would also define DISTRO_BLEEDING_HPC or
DISTRO_BLEEDING_RT, respectively.
Does that make sense, or am I being overly naive?
Thanx, Paul
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