linux-kernel - Re: [PATCH 1/2] rcu: Fix full dynticks' dependency on wide RCU nocb mode

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Date:	Fri, 3 May 2013 09:58:44 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	Ingo Molnar <mingo@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Christoph Lameter <cl@...ux.com>,
	Hakan Akkan <hakanakkan@...il.com>,
	Kevin Hilman <khilman@...aro.org>,
	Li Zhong <zhong@...ux.vnet.ibm.com>,
	Paul Gortmaker <paul.gortmaker@...driver.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 1/2] rcu: Fix full dynticks' dependency on wide RCU nocb
 mode

On Fri, May 03, 2013 at 06:47:55PM +0200, Frederic Weisbecker wrote:
> Commit 0637e029392386e6996f5d6574aadccee8315efa
> ("nohz: Select wide RCU nocb for full dynticks") intended
> to force CONFIG_RCU_NOCB_CPU_ALL=y when full dynticks is
> enabled.
> 
> However this option is part of a choice menu and Kconfig's
> "select" instruction has no effect on such targets.
> 
> Fix this by using reverse dependencies on the targets we
> don't want instead.
> 
> Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
> Cc: Christoph Lameter <cl@...ux.com>
> Cc: Hakan Akkan <hakanakkan@...il.com>
> Cc: Ingo Molnar <mingo@...nel.org>
> Cc: Kevin Hilman <khilman@...aro.org>
> Cc: Li Zhong <zhong@...ux.vnet.ibm.com>
> Cc: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
> Cc: Paul Gortmaker <paul.gortmaker@...driver.com>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Steven Rostedt <rostedt@...dmis.org>
> Cc: Thomas Gleixner <tglx@...utronix.de>

Reviewed-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>

> ---
>  init/Kconfig        |    4 ++--
>  kernel/time/Kconfig |    1 -
>  2 files changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/init/Kconfig b/init/Kconfig
> index 66f67af..b3fdf9a 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -687,7 +687,7 @@ choice
> 
>  config RCU_NOCB_CPU_NONE
>  	bool "No build_forced no-CBs CPUs"
> -	depends on RCU_NOCB_CPU
> +	depends on RCU_NOCB_CPU && !NO_HZ_FULL
>  	help
>  	  This option does not force any of the CPUs to be no-CBs CPUs.
>  	  Only CPUs designated by the rcu_nocbs= boot parameter will be
> @@ -695,7 +695,7 @@ config RCU_NOCB_CPU_NONE
> 
>  config RCU_NOCB_CPU_ZERO
>  	bool "CPU 0 is a build_forced no-CBs CPU"
> -	depends on RCU_NOCB_CPU
> +	depends on RCU_NOCB_CPU && !NO_HZ_FULL
>  	help
>  	  This option forces CPU 0 to be a no-CBs CPU.  Additional CPUs
>  	  may be designated as no-CBs CPUs using the rcu_nocbs= boot
> diff --git a/kernel/time/Kconfig b/kernel/time/Kconfig
> index a2ddd65..e4c07b0 100644
> --- a/kernel/time/Kconfig
> +++ b/kernel/time/Kconfig
> @@ -109,7 +109,6 @@ config NO_HZ_FULL
>  	select NO_HZ_COMMON
>  	select RCU_USER_QS
>  	select RCU_NOCB_CPU
> -	select RCU_NOCB_CPU_ALL
>  	select VIRT_CPU_ACCOUNTING_GEN
>  	select CONTEXT_TRACKING_FORCE
>  	select IRQ_WORK
> -- 
> 1.7.5.4
> 

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