Re: [PATCH] move PREEMPT_RCU config option back under PREEMPT

From: Paul E. McKenney
Date: Tue Mar 04 2008 - 19:58:41 EST


On Tue, Mar 04, 2008 at 03:55:42PM -0500, Steven Rostedt wrote:
>
> On Tue, 4 Mar 2008, Paul E. McKenney wrote:
> >
> > The original preemptible-RCU patch put the choice between classic and
> > preemptible RCU into kernel/Kconfig.preempt, which resulted in build
> > failures on machines not supporting CONFIG_PREEMPT. This choice was
> > therefore moved to init/Kconfig, which worked, but placed the choice
> > between classic and preemptible RCU at the top level, a very obtuse choice
> > indeed. This patch changes from the Kconfig "choice" mechanism to a pair
> > of booleans, only one of which (CONFIG_PREEMPT_RCU) is user-visible,
> > and is located in kernel/Kconfig.preempt, where one would expect it
> > to be. The other (CONFIG_CLASSIC_RCU) is in init/Kconfig so that it
> > is available to all architectures, hopefully avoiding build breakage.
> > Thanks to Roman Zippel for suggesting this approach.
> >
> > I have tested this, but sadly do not have access to a machine that does
> > not support CONFIG_PREEMPT. However, I did edit my config in an attempt
> > to simulate this situation.
>
> One minor comment, but otherwise:
>
> Acked-by: Steven Rostedt <srostedt@xxxxxxxxxx>
>
> >
> > Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
>
>
> > config CLASSIC_RCU
> > - bool "Classic RCU"
> > + def_bool !PREEMPT_RCU
> > help
> > This option selects the classic RCU implementation that is
> > designed for best read-side performance on non-realtime
> > - systems.
> > -
> > - Say Y if you are unsure.
> > -
>
> You can get rid of the "help" part since it isn't visible to users.

So how about if I replace it with comment lines (starting with "#",
not with "comment")?

Thanx, Paul
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