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

[Steven Rostedt <rostedt@goodmis.org>]

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@redhat.com>

>
> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>


>  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.

-- Steve