rcu: Add last-CPU to GP-kthread starvation messages

This commit augments the grace-period-kthread starvation debugging
messages by adding the last CPU that ran the kthread.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

kernel/rcu/tree.c

@@ -1358,12 +1358,13 @@ static void rcu_check_gp_kthread_starvation(struct rcu_state *rsp)
 	j = jiffies;
 	gpa = READ_ONCE(rsp->gp_activity);
 	if (j - gpa > 2 * HZ) {
-		pr_err("%s kthread starved for %ld jiffies! g%lu c%lu f%#x %s(%d) ->state=%#lx\n",
+		pr_err("%s kthread starved for %ld jiffies! g%lu c%lu f%#x %s(%d) ->state=%#lx ->cpu=%d\n",
 		       rsp->name, j - gpa,
 		       rsp->gpnum, rsp->completed,
 		       rsp->gp_flags,
 		       gp_state_getname(rsp->gp_state), rsp->gp_state,
-		       rsp->gp_kthread ? rsp->gp_kthread->state : ~0);
+		       rsp->gp_kthread ? rsp->gp_kthread->state : ~0,
+		       rsp->gp_kthread ? task_cpu(rsp->gp_kthread) : -1);
 		if (rsp->gp_kthread) {
 			sched_show_task(rsp->gp_kthread);
 			wake_up_process(rsp->gp_kthread);