srcu: Add address of first callback to rcutorture output

This commit adds the address of the first callback to the per-CPU rcutorture
output in order to allow lost wakeups to be more efficiently tracked down.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

kernel/rcu/srcutree.c

@@ -1271,11 +1271,11 @@ void srcu_torture_stats_print(struct srcu_struct *sp, char *tt, char *tf)
 		unsigned long l0, l1;
 		unsigned long u0, u1;
 		long c0, c1;
-		struct srcu_data *counts;
+		struct srcu_data *sdp;
 
-		counts = per_cpu_ptr(sp->sda, cpu);
-		u0 = counts->srcu_unlock_count[!idx];
-		u1 = counts->srcu_unlock_count[idx];
+		sdp = per_cpu_ptr(sp->sda, cpu);
+		u0 = sdp->srcu_unlock_count[!idx];
+		u1 = sdp->srcu_unlock_count[idx];
 
 		/*
 		 * Make sure that a lock is always counted if the corresponding
@@ -1283,12 +1283,13 @@ void srcu_torture_stats_print(struct srcu_struct *sp, char *tt, char *tf)
 		 */
 		smp_rmb();
 
-		l0 = counts->srcu_lock_count[!idx];
-		l1 = counts->srcu_lock_count[idx];
+		l0 = sdp->srcu_lock_count[!idx];
+		l1 = sdp->srcu_lock_count[idx];
 
 		c0 = l0 - u0;
 		c1 = l1 - u1;
-		pr_cont(" %d(%ld,%ld)", cpu, c0, c1);
+		pr_cont(" %d(%ld,%ld %1p)",
+			cpu, c0, c1, rcu_segcblist_head(&sdp->srcu_cblist));
 		s0 += c0;
 		s1 += c1;
 	}