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

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Date:	Fri,  3 May 2013 18:47:55 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Christoph Lameter <cl@...ux.com>,
	Hakan Akkan <hakanakkan@...il.com>,
	Kevin Hilman <khilman@...aro.org>,
	Li Zhong <zhong@...ux.vnet.ibm.com>,
	"Paul E. McKenney" <paulmck@...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: [PATCH 1/2] rcu: Fix full dynticks' dependency on wide RCU nocb mode

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>
---
 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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