rcu: Remove obsolete force-quiescent-state statistics for debugfs

The debugfs interface displayed statistics on RCU-pending checks but
this interface has since been removed.  This commit therefore removes the
no-longer-used rcu_state structure's ->n_force_qs_lh and ->n_force_qs_ngp
fields along with their updates.  (Though the ->n_force_qs_ngp field
was actually not used at all, embarrassingly enough.)

If this information proves necessary in the future, the corresponding
event traces will be added.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

kernel/rcu/tree.c

@@ -2844,10 +2844,8 @@ static void force_quiescent_state(struct rcu_state *rsp)
 		      !raw_spin_trylock(&rnp->fqslock);
 		if (rnp_old != NULL)
 			raw_spin_unlock(&rnp_old->fqslock);
-		if (ret) {
-			rsp->n_force_qs_lh++;
+		if (ret)
 			return;
-		}
 		rnp_old = rnp;
 	}
 	/* rnp_old == rcu_get_root(rsp), rnp == NULL. */
@@ -2856,7 +2854,6 @@ static void force_quiescent_state(struct rcu_state *rsp)
 	raw_spin_lock_irqsave_rcu_node(rnp_old, flags);
 	raw_spin_unlock(&rnp_old->fqslock);
 	if (READ_ONCE(rsp->gp_flags) & RCU_GP_FLAG_FQS) {
-		rsp->n_force_qs_lh++;
 		raw_spin_unlock_irqrestore_rcu_node(rnp_old, flags);
 		return;  /* Someone beat us to it. */
 	}

kernel/rcu/tree.h

@@ -355,10 +355,6 @@ struct rcu_state {
 						/*  kthreads, if configured. */
 	unsigned long n_force_qs;		/* Number of calls to */
 						/*  force_quiescent_state(). */
-	unsigned long n_force_qs_lh;		/* ~Number of calls leaving */
-						/*  due to lock unavailable. */
-	unsigned long n_force_qs_ngp;		/* Number of calls leaving */
-						/*  due to no GP active. */
 	unsigned long gp_start;			/* Time at which GP started, */
 						/*  but in jiffies. */
 	unsigned long gp_activity;		/* Time of last GP kthread */