rcu: Rename ->onofflock to ->orphan_lock

The ->onofflock field in the rcu_state structure at one time synchronized
CPU-hotplug operations for RCU.  However, its scope has decreased over time
so that it now only protects the lists of orphaned RCU callbacks.  This
commit therefore renames it to ->orphan_lock to reflect its current use.

Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index ac8aed8..8914886 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -70,7 +70,7 @@
 	.fqs_state = RCU_GP_IDLE, \
 	.gpnum = -300, \
 	.completed = -300, \
-	.onofflock = __RAW_SPIN_LOCK_UNLOCKED(&sname##_state.onofflock), \
+	.orphan_lock = __RAW_SPIN_LOCK_UNLOCKED(&sname##_state.orphan_lock), \
 	.orphan_nxttail = &sname##_state.orphan_nxtlist, \
 	.orphan_donetail = &sname##_state.orphan_donelist, \
 	.barrier_mutex = __MUTEX_INITIALIZER(sname##_state.barrier_mutex), \
@@ -1573,7 +1573,7 @@
 /*
  * Send the specified CPU's RCU callbacks to the orphanage.  The
  * specified CPU must be offline, and the caller must hold the
- * ->onofflock.
+ * ->orphan_lock.
  */
 static void
 rcu_send_cbs_to_orphanage(int cpu, struct rcu_state *rsp,
@@ -1623,7 +1623,7 @@
 
 /*
  * Adopt the RCU callbacks from the specified rcu_state structure's
- * orphanage.  The caller must hold the ->onofflock.
+ * orphanage.  The caller must hold the ->orphan_lock.
  */
 static void rcu_adopt_orphan_cbs(struct rcu_state *rsp)
 {
@@ -1702,7 +1702,7 @@
 
 	/* Exclude any attempts to start a new grace period. */
 	mutex_lock(&rsp->onoff_mutex);
-	raw_spin_lock_irqsave(&rsp->onofflock, flags);
+	raw_spin_lock_irqsave(&rsp->orphan_lock, flags);
 
 	/* Orphan the dead CPU's callbacks, and adopt them if appropriate. */
 	rcu_send_cbs_to_orphanage(cpu, rsp, rnp, rdp);
@@ -1729,10 +1729,10 @@
 	/*
 	 * We still hold the leaf rcu_node structure lock here, and
 	 * irqs are still disabled.  The reason for this subterfuge is
-	 * because invoking rcu_report_unblock_qs_rnp() with ->onofflock
+	 * because invoking rcu_report_unblock_qs_rnp() with ->orphan_lock
 	 * held leads to deadlock.
 	 */
-	raw_spin_unlock(&rsp->onofflock); /* irqs remain disabled. */
+	raw_spin_unlock(&rsp->orphan_lock); /* irqs remain disabled. */
 	rnp = rdp->mynode;
 	if (need_report & RCU_OFL_TASKS_NORM_GP)
 		rcu_report_unblock_qs_rnp(rnp, flags);