linux-kernel - Re: [PATCH tip/core/rcu 14/26] rcu: Userspace RCU extended QS selftest

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Message-ID: <20120831235446.GK11771@jtriplet-mobl1>
Date:	Fri, 31 Aug 2012 16:54:46 -0700
From:	Josh Triplett <josh@...htriplett.org>
To:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:	linux-kernel@...r.kernel.org, mingo@...e.hu, laijs@...fujitsu.com,
	dipankar@...ibm.com, akpm@...ux-foundation.org,
	mathieu.desnoyers@...ymtl.ca, niv@...ibm.com, tglx@...utronix.de,
	peterz@...radead.org, rostedt@...dmis.org, Valdis.Kletnieks@...edu,
	dhowells@...hat.com, eric.dumazet@...il.com, darren@...art.com,
	fweisbec@...il.com, sbw@....edu, patches@...aro.org,
	Alessio Igor Bogani <abogani@...nel.org>,
	Avi Kivity <avi@...hat.com>,
	Chris Metcalf <cmetcalf@...era.com>,
	Christoph Lameter <cl@...ux.com>,
	Geoff Levand <geoff@...radead.org>,
	Gilad Ben Yossef <gilad@...yossef.com>,
	Hakan Akkan <hakanakkan@...il.com>,
	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...nel.org>,
	Kevin Hilman <khilman@...com>,
	Max Krasnyansky <maxk@...lcomm.com>,
	Stephen Hemminger <shemminger@...tta.com>,
	Sven-Thorsten Dietrich <thebigcorporation@...il.com>
Subject: Re: [PATCH tip/core/rcu 14/26] rcu: Userspace RCU extended QS
 selftest

On Thu, Aug 30, 2012 at 02:05:31PM -0700, Paul E. McKenney wrote:
> From: Frederic Weisbecker <fweisbec@...il.com>
> 
> Provide a config option that enables the userspace
> RCU extended quiescent state on every CPUs by default.
> 
> This is for testing purpose.
> 
> Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
> Cc: Alessio Igor Bogani <abogani@...nel.org>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Avi Kivity <avi@...hat.com>
> Cc: Chris Metcalf <cmetcalf@...era.com>
> Cc: Christoph Lameter <cl@...ux.com>
> Cc: Geoff Levand <geoff@...radead.org>
> Cc: Gilad Ben Yossef <gilad@...yossef.com>
> Cc: Hakan Akkan <hakanakkan@...il.com>
> Cc: H. Peter Anvin <hpa@...or.com>
> Cc: Ingo Molnar <mingo@...nel.org>
> Cc: Josh Triplett <josh@...htriplett.org>
> Cc: Kevin Hilman <khilman@...com>
> Cc: Max Krasnyansky <maxk@...lcomm.com>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Stephen Hemminger <shemminger@...tta.com>
> Cc: Steven Rostedt <rostedt@...dmis.org>
> Cc: Sven-Thorsten Dietrich <thebigcorporation@...il.com>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>

Reviewed-by: Josh Triplett <josh@...htriplett.org>

>  init/Kconfig     |    8 ++++++++
>  kernel/rcutree.c |    2 +-
>  2 files changed, 9 insertions(+), 1 deletions(-)
> 
> diff --git a/init/Kconfig b/init/Kconfig
> index f6a1830..c26b8a1 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -451,6 +451,14 @@ config RCU_USER_QS
>  	  excluded from the global RCU state machine and thus doesn't
>  	  to keep the timer tick on for RCU.
>  
> +config RCU_USER_QS_FORCE
> +	bool "Force userspace extended QS by default"
> +	depends on RCU_USER_QS
> +	help
> +	  Set the hooks in user/kernel boundaries by default in order to
> +	  test this feature that treats userspace as an extended quiescent
> +	  state until we have a real user like a full adaptive nohz option.
> +
>  config RCU_FANOUT
>  	int "Tree-based hierarchical RCU fanout value"
>  	range 2 64 if 64BIT
> diff --git a/kernel/rcutree.c b/kernel/rcutree.c
> index af92681..ccf3cbf 100644
> --- a/kernel/rcutree.c
> +++ b/kernel/rcutree.c
> @@ -210,7 +210,7 @@ EXPORT_SYMBOL_GPL(rcu_note_context_switch);
>  DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = {
>  	.dynticks_nesting = DYNTICK_TASK_EXIT_IDLE,
>  	.dynticks = ATOMIC_INIT(1),
> -#ifdef CONFIG_RCU_USER_QS
> +#if defined(CONFIG_RCU_USER_QS) && !defined(CONFIG_RCU_USER_QS_FORCE)
>  	.ignore_user_qs = true,
>  #endif
>  };
> -- 
> 1.7.8
> 
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