rcu: Remove unused rcu_cpu_kthread_loops per-CPU variable

The rcu_cpu_kthread_loops variable used to provide debugfs information,
but is no longer used.  This commit therefore removes it.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>

kernel/rcu/tree.h

@@ -410,7 +410,6 @@ int rcu_dynticks_snap(struct rcu_data *rdp);
 
 #ifdef CONFIG_RCU_BOOST
 DECLARE_PER_CPU(int, rcu_cpu_kthread_cpu);
-DECLARE_PER_CPU(unsigned int, rcu_cpu_kthread_loops);
 DECLARE_PER_CPU(char, rcu_cpu_has_work);
 #endif /* #ifdef CONFIG_RCU_BOOST */
 

kernel/rcu/tree_plugin.h

@@ -40,7 +40,6 @@
 /*
  * Control variables for per-CPU and per-rcu_node kthreads.
  */
-DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_loops);
 DEFINE_PER_CPU(char, rcu_cpu_has_work);
 
 #else /* #ifdef CONFIG_RCU_BOOST */
@@ -1405,7 +1404,6 @@ static void rcu_cpu_kthread(unsigned int cpu)
 		trace_rcu_utilization(TPS("Start CPU kthread@rcu_wait"));
 		local_bh_disable();
 		*statusp = RCU_KTHREAD_RUNNING;
-		this_cpu_inc(rcu_cpu_kthread_loops);
 		local_irq_disable();
 		work = *workp;
 		*workp = 0;