linux-kernel - [PATCH tip/core/rcu 15/24] rcu: Directly drive RCU_USER

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Message-Id: <1431469854-3826-15-git-send-email-paulmck@linux.vnet.ibm.com>
Date:	Tue, 12 May 2015 15:30:45 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	linux-kernel@...r.kernel.org
Cc:	mingo@...nel.org, laijs@...fujitsu.com, dipankar@...ibm.com,
	akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com,
	josh@...htriplett.org, tglx@...utronix.de, peterz@...radead.org,
	rostedt@...dmis.org, dhowells@...hat.com, edumazet@...gle.com,
	dvhart@...ux.intel.com, fweisbec@...il.com, oleg@...hat.com,
	bobby.prani@...il.com,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: [PATCH tip/core/rcu 15/24] rcu: Directly drive RCU_USER_QS from Kconfig

From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>

Currently, Kconfig will ask the user whether RCU_USER_QS should be set.
This is silly because Kconfig already has all the information that it
needs to set this parameter.  This commit therefore directly drives
the value of RCU_USER_QS via NO_HZ_FULL's "select" statement.

Reported-by: Ingo Molnar <mingo@...nel.org>
Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
Cc: Frederic Weisbecker <fweisbec@...il.com>
Reviewed-by: Pranith Kumar <bobby.prani@...il.com>
---
 init/Kconfig | 10 +---------
 1 file changed, 1 insertion(+), 9 deletions(-)

diff --git a/init/Kconfig b/init/Kconfig
index 73db30a76afa..927210810189 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -529,9 +529,7 @@ config CONTEXT_TRACKING
        bool
 
 config RCU_USER_QS
-	bool "Consider userspace as in RCU extended quiescent state"
-	depends on HAVE_CONTEXT_TRACKING && SMP
-	select CONTEXT_TRACKING
+	bool
 	help
 	  This option sets hooks on kernel / userspace boundaries and
 	  puts RCU in extended quiescent state when the CPU runs in
@@ -539,12 +537,6 @@ config RCU_USER_QS
 	  excluded from the global RCU state machine and thus doesn't
 	  try to keep the timer tick on for RCU.
 
-	  Unless you want to hack and help the development of the full
-	  dynticks mode, you shouldn't enable this option.  It also
-	  adds unnecessary overhead.
-
-	  If unsure say N
-
 config CONTEXT_TRACKING_FORCE
 	bool "Force context tracking"
 	depends on CONTEXT_TRACKING
-- 
1.8.1.5

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