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

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Date:	Thu, 30 Aug 2012 14:05:31 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	linux-kernel@...r.kernel.org
Cc:	mingo@...e.hu, laijs@...fujitsu.com, dipankar@...ibm.com,
	akpm@...ux-foundation.org, mathieu.desnoyers@...ymtl.ca,
	josh@...htriplett.org, 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>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: [PATCH tip/core/rcu 14/26] rcu: Userspace RCU extended QS selftest

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>
---
 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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