rcu: Settle config for userspace extended quiescent state

Create a new config option under the RCU menu that put
CPUs under RCU extended quiescent state (as in dynticks
idle mode) when they run in userspace. This require
some contribution from architectures to hook into kernel
and userspace boundaries.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Alessio Igor Bogani <abogani@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Avi Kivity <avi@redhat.com>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Geoff Levand <geoff@infradead.org>
Cc: Gilad Ben Yossef <gilad@benyossef.com>
Cc: Hakan Akkan <hakanakkan@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Kevin Hilman <khilman@ti.com>
Cc: Max Krasnyansky <maxk@qualcomm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephen Hemminger <shemminger@vyatta.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Sven-Thorsten Dietrich <thebigcorporation@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

1 files changed, 4 insertions, 1 deletions

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 4138f59fa2f4..79fa2db1595b 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -400,6 +400,7 @@ void rcu_idle_enter(void)
 }
 EXPORT_SYMBOL_GPL(rcu_idle_enter);
 
+#ifdef CONFIG_RCU_USER_QS
 /**
  * rcu_user_enter - inform RCU that we are resuming userspace.
  *
@@ -424,7 +425,6 @@ void rcu_user_enter(void)
         rcu_eqs_enter(1);
 }
 
-
 /**
  * rcu_user_enter_after_irq - inform RCU that we are going to resume userspace
  * after the current irq returns.
@@ -445,6 +445,7 @@ void rcu_user_enter_after_irq(void)
         rdtp->dynticks_nesting = 1;
         local_irq_restore(flags);
 }
+#endif /* CONFIG_RCU_USER_QS */
 
 /**
  * rcu_irq_exit - inform RCU that current CPU is exiting irq towards idle
@@ -548,6 +549,7 @@ void rcu_idle_exit(void)
 }
 EXPORT_SYMBOL_GPL(rcu_idle_exit);
 
+#ifdef CONFIG_RCU_USER_QS
 /**
  * rcu_user_exit - inform RCU that we are exiting userspace.
  *
@@ -591,6 +593,7 @@ void rcu_user_exit_after_irq(void)
         rdtp->dynticks_nesting += DYNTICK_TASK_EXIT_IDLE;
         local_irq_restore(flags);
 }
+#endif /* CONFIG_RCU_USER_QS */
 
 /**
  * rcu_irq_enter - inform RCU that current CPU is entering irq away from idle