Merge branch 'idle.2013.09.25a' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu into HEAD

Need to use Paul McKenney's "rcu_is_watching()" changes to fix
a perf/ftrace bug.

1 files changed, 18 insertions, 5 deletions

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 32618b3fe4e..981d0c15a38 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -655,21 +655,34 @@ void rcu_nmi_exit(void)
 }
 
 /**
- * rcu_is_cpu_idle - see if RCU thinks that the current CPU is idle
+ * __rcu_is_watching - are RCU read-side critical sections safe?
+ *
+ * Return true if RCU is watching the running CPU, which means that
+ * this CPU can safely enter RCU read-side critical sections.  Unlike
+ * rcu_is_watching(), the caller of __rcu_is_watching() must have at
+ * least disabled preemption.
+ */
+bool __rcu_is_watching(void)
+{
+	return atomic_read(this_cpu_ptr(&rcu_dynticks.dynticks)) & 0x1;
+}
+
+/**
+ * rcu_is_watching - see if RCU thinks that the current CPU is idle
  *
  * If the current CPU is in its idle loop and is neither in an interrupt
  * or NMI handler, return true.
  */
-int rcu_is_cpu_idle(void)
+bool rcu_is_watching(void)
 {
 	int ret;
 
 	preempt_disable();
-	ret = (atomic_read(&__get_cpu_var(rcu_dynticks).dynticks) & 0x1) == 0;
+	ret = __rcu_is_watching();
 	preempt_enable();
 	return ret;
 }
-EXPORT_SYMBOL(rcu_is_cpu_idle);
+EXPORT_SYMBOL_GPL(rcu_is_watching);
 
 #if defined(CONFIG_PROVE_RCU) && defined(CONFIG_HOTPLUG_CPU)
 
@@ -2255,7 +2268,7 @@ static void __call_rcu_core(struct rcu_state *rsp, struct rcu_data *rdp,
 	 * If called from an extended quiescent state, invoke the RCU
 	 * core in order to force a re-evaluation of RCU's idleness.
 	 */
-	if (rcu_is_cpu_idle() && cpu_online(smp_processor_id()))
+	if (!rcu_is_watching() && cpu_online(smp_processor_id()))
 		invoke_rcu_core();
 
 	/* If interrupts were disabled or CPU offline, don't invoke RCU core. */