rcutorture: Expedited-GP batch progress access to torturing

This commit provides rcu_exp_batches_completed() and
rcu_exp_batches_completed_sched() functions to allow torture-test modules
to check how many expedited grace period batches have completed.
These are analogous to the existing rcu_batches_completed(),
rcu_batches_completed_bh(), and rcu_batches_completed_sched() functions.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

include/linux/rcutiny.h

@@ -149,6 +149,22 @@ static inline unsigned long rcu_batches_completed_sched(void)
 	return 0;
 }
 
+/*
+ * Return the number of expedited grace periods completed.
+ */
+static inline unsigned long rcu_exp_batches_completed(void)
+{
+	return 0;
+}
+
+/*
+ * Return the number of expedited sched grace periods completed.
+ */
+static inline unsigned long rcu_exp_batches_completed_sched(void)
+{
+	return 0;
+}
+
 static inline void rcu_force_quiescent_state(void)
 {
 }

include/linux/rcutree.h

@@ -87,6 +87,8 @@ unsigned long rcu_batches_started_sched(void);
 unsigned long rcu_batches_completed(void);
 unsigned long rcu_batches_completed_bh(void);
 unsigned long rcu_batches_completed_sched(void);
+unsigned long rcu_exp_batches_completed(void);
+unsigned long rcu_exp_batches_completed_sched(void);
 void show_rcu_gp_kthreads(void);
 
 void rcu_force_quiescent_state(void);

kernel/rcu/tree.c

@@ -459,6 +459,28 @@ unsigned long rcu_batches_completed_bh(void)
 }
 EXPORT_SYMBOL_GPL(rcu_batches_completed_bh);
 
+/*
+ * Return the number of RCU expedited batches completed thus far for
+ * debug & stats.  Odd numbers mean that a batch is in progress, even
+ * numbers mean idle.  The value returned will thus be roughly double
+ * the cumulative batches since boot.
+ */
+unsigned long rcu_exp_batches_completed(void)
+{
+	return rcu_state_p->expedited_sequence;
+}
+EXPORT_SYMBOL_GPL(rcu_exp_batches_completed);
+
+/*
+ * Return the number of RCU-sched expedited batches completed thus far
+ * for debug & stats.  Similar to rcu_exp_batches_completed().
+ */
+unsigned long rcu_exp_batches_completed_sched(void)
+{
+	return rcu_sched_state.expedited_sequence;
+}
+EXPORT_SYMBOL_GPL(rcu_exp_batches_completed_sched);
+
 /*
  * Force a quiescent state.
  */