rcu: Add RCU_NONIDLE() for idle-loop RCU read-side critical sections

RCU, RCU-bh, and RCU-sched read-side critical sections are forbidden
in the inner idle loop, that is, between the rcu_idle_enter() and the
rcu_idle_exit() -- RCU will happily ignore any such read-side critical
sections.  However, things like powertop need tracepoints in the inner
idle loop.

This commit therefore provides an RCU_NONIDLE() macro that can be used to
wrap code in the idle loop that requires RCU read-side critical sections.

Suggested-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Acked-by: Deepthi Dharwar <deepthi@linux.vnet.ibm.com>

2 files changed, 4 insertions, 0 deletions

diff --git a/kernel/rcutiny.c b/kernel/rcutiny.c
index c8b0e1582c04..37a5444204d2 100644
--- a/kernel/rcutiny.c
+++ b/kernel/rcutiny.c
@@ -97,6 +97,7 @@ void rcu_idle_enter(void)
         rcu_idle_enter_common(oldval);
         local_irq_restore(flags);
 }
+EXPORT_SYMBOL_GPL(rcu_idle_enter);
 
 /*
  * Exit an interrupt handler towards idle.
@@ -153,6 +154,7 @@ void rcu_idle_exit(void)
         rcu_idle_exit_common(oldval);
         local_irq_restore(flags);
 }
+EXPORT_SYMBOL_GPL(rcu_idle_exit);
 
 /*
  * Enter an interrupt handler, moving away from idle.
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 92b47760edf3..eacc10b03531 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -402,6 +402,7 @@ void rcu_idle_enter(void)
         rcu_idle_enter_common(rdtp, oldval);
         local_irq_restore(flags);
 }
+EXPORT_SYMBOL_GPL(rcu_idle_enter);
 
 /**
  * rcu_irq_exit - inform RCU that current CPU is exiting irq towards idle
@@ -493,6 +494,7 @@ void rcu_idle_exit(void)
         rcu_idle_exit_common(rdtp, oldval);
         local_irq_restore(flags);
 }
+EXPORT_SYMBOL_GPL(rcu_idle_exit);
 
 /**
  * rcu_irq_enter - inform RCU that current CPU is entering irq away from idle