linux-kernel - Re: [PATCH] make CONFIG_EXPERIMENTAL invisible and default

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Message-ID: <20121003193653.GB30477@redhat.com>
Date:	Wed, 3 Oct 2012 15:36:53 -0400
From:	Dave Jones <davej@...hat.com>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Kees Cook <keescook@...omium.org>,
	linux-kernel@...r.kernel.org,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Serge Hallyn <serge.hallyn@...onical.com>,
	"David S. Miller" <davem@...emloft.net>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] make CONFIG_EXPERIMENTAL invisible and default

On Wed, Oct 03, 2012 at 07:46:18PM +0200, Frederic Weisbecker wrote:
 > > it in the kernel tree, unless we wanted people to use the option?
 > 
 > A solution could be to add that option under CONFIG_DEBUG_KERNEL and specify
 > that it must only be enabled by developers for specific reasons (overhead,
 > security). CONFIG_PROVE_LOCKING falls into that category, right?
 > 
 > We have CONFIG_RCU_USER_QS that is a specific case. It's an intermediate state
 > before we implement a true CONFIG_NO_HZ_FULL. But the option is useless on its
 > own for users. Worse, it introduces a real overhead. OTOH we want it to be upstream
 > to make the development of full tickless feature more incremental.
 > 
 > Perhaps we should put that under CONFIG_DEBUG_KERNEL.

Overloading an existing config option for something unrelated seems unpleasant to me.
It will only take a few people to start doing this, before it turns into a landslide
where everyone ends up with DEBUG_KERNEL set.
And what of people who already have DEBUG_KERNEL set ?

Just state what you wrote above in the kconfig.
Currently, RCU_USER_QS says nothing about the fact that it's work in progress.

The missing part that I don't have an answer for however, is what happens
when you deem this production ready? Distro maintainers won't notice the
kconfig text changing. But perhaps that's a good thing, and will lead to things
only being enabled when people explicitly ask for them in distros.

Alternatively, if you really do want to go the path of a new config option,
perhaps CONFIG_NOT_DISTRO_READY would spell things out more clearly.
EXPERIMENTAL is such a wasteland it would take too much manpower to audit
every case, and update accordingly, but scorching the earth and starting
afresh might be feasible.

	Dave

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