diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index 8ee8e4e0a2ba4d002fd22d986c1ceec22f9ee6b0..918d222408560dc413c7c47cecf758a10ef5939a 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -932,31 +932,26 @@ static int throtl_select_dispatch(struct throtl_service_queue *parent_sq)
 	return nr_disp;
 }
 
+/**
+ * throtl_pending_timer_fn - timer function for service_queue->pending_timer
+ * @arg: the throtl_service_queue being serviced
+ *
+ * This timer is armed when a child throtl_grp with active bio's become
+ * pending and queued on the service_queue's pending_tree and expires when
+ * the first child throtl_grp should be dispatched.  This function
+ * dispatches bio's from the children throtl_grps and kicks
+ * throtl_data->dispatch_work if there are bio's ready to be issued.
+ */
 static void throtl_pending_timer_fn(unsigned long arg)
 {
 	struct throtl_service_queue *sq = (void *)arg;
 	struct throtl_data *td = sq_to_td(sq);
-
-	queue_work(kthrotld_workqueue, &td->dispatch_work);
-}
-
-/* work function to dispatch throttled bios */
-void blk_throtl_dispatch_work_fn(struct work_struct *work)
-{
-	struct throtl_data *td = container_of(work, struct throtl_data,
-					      dispatch_work);
-	struct throtl_service_queue *sq = &td->service_queue;
 	struct request_queue *q = td->queue;
-	struct bio_list bio_list_on_stack;
-	struct bio *bio;
-	struct blk_plug plug;
 	bool dispatched = false;
-	int rw, ret;
+	int ret;
 
 	spin_lock_irq(q->queue_lock);
 
-	bio_list_init(&bio_list_on_stack);
-
 	while (true) {
 		throtl_log(sq, "dispatch nr_queued=%u read=%u write=%u",
 			   td->nr_queued[READ] + td->nr_queued[WRITE],
@@ -964,10 +959,6 @@ void blk_throtl_dispatch_work_fn(struct work_struct *work)
 
 		ret = throtl_select_dispatch(sq);
 		if (ret) {
-			for (rw = READ; rw <= WRITE; rw++) {
-				bio_list_merge(&bio_list_on_stack, &sq->bio_lists[rw]);
-				bio_list_init(&sq->bio_lists[rw]);
-			}
 			throtl_log(sq, "bios disp=%u", ret);
 			dispatched = true;
 		}
@@ -981,13 +972,41 @@ void blk_throtl_dispatch_work_fn(struct work_struct *work)
 		spin_lock_irq(q->queue_lock);
 	}
 
+	if (dispatched)
+		queue_work(kthrotld_workqueue, &td->dispatch_work);
+
 	spin_unlock_irq(q->queue_lock);
+}
 
-	/*
-	 * If we dispatched some requests, unplug the queue to make sure
-	 * immediate dispatch
-	 */
-	if (dispatched) {
+/**
+ * blk_throtl_dispatch_work_fn - work function for throtl_data->dispatch_work
+ * @work: work item being executed
+ *
+ * This function is queued for execution when bio's reach the bio_lists[]
+ * of throtl_data->service_queue.  Those bio's are ready and issued by this
+ * function.
+ */
+void blk_throtl_dispatch_work_fn(struct work_struct *work)
+{
+	struct throtl_data *td = container_of(work, struct throtl_data,
+					      dispatch_work);
+	struct throtl_service_queue *td_sq = &td->service_queue;
+	struct request_queue *q = td->queue;
+	struct bio_list bio_list_on_stack;
+	struct bio *bio;
+	struct blk_plug plug;
+	int rw;
+
+	bio_list_init(&bio_list_on_stack);
+
+	spin_lock_irq(q->queue_lock);
+	for (rw = READ; rw <= WRITE; rw++) {
+		bio_list_merge(&bio_list_on_stack, &td_sq->bio_lists[rw]);
+		bio_list_init(&td_sq->bio_lists[rw]);
+	}
+	spin_unlock_irq(q->queue_lock);
+
+	if (!bio_list_empty(&bio_list_on_stack)) {
 		blk_start_plug(&plug);
 		while((bio = bio_list_pop(&bio_list_on_stack)))
 			generic_make_request(bio);