1 files changed, 69 insertions, 11 deletions

diff --git a/drivers/connector/cn_queue.c b/drivers/connector/cn_queue.c
index b6fe7e7..c769ef2 100644
--- a/drivers/connector/cn_queue.c
+++ b/drivers/connector/cn_queue.c
@@ -1,9 +1,9 @@
 /*
  * 	cn_queue.c
- * 
+ *
  * 2004-2005 Copyright (c) Evgeniy Polyakov <johnpol@2ka.mipt.ru>
  * All rights reserved.
- * 
+ *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
  * the Free Software Foundation; either version 2 of the License, or
@@ -31,6 +31,48 @@
 #include <linux/connector.h>
 #include <linux/delay.h>
 
+
+/*
+ * This job is sent to the kevent workqueue.
+ * While no event is once sent to any callback, the connector workqueue
+ * is not created to avoid a useless waiting kernel task.
+ * Once the first event is received, we create this dedicated workqueue which
+ * is necessary because the flow of data can be high and we don't want
+ * to encumber keventd with that.
+ */
+static void cn_queue_create(struct work_struct *work)
+{
+	struct cn_queue_dev *dev;
+
+	dev = container_of(work, struct cn_queue_dev, wq_creation);
+
+	dev->cn_queue = create_singlethread_workqueue(dev->name);
+	/* If we fail, we will use keventd for all following connector jobs */
+	WARN_ON(!dev->cn_queue);
+}
+
+/*
+ * Queue a data sent to a callback.
+ * If the connector workqueue is already created, we queue the job on it.
+ * Otherwise, we queue the job to kevent and queue the connector workqueue
+ * creation too.
+ */
+int queue_cn_work(struct cn_callback_entry *cbq, struct work_struct *work)
+{
+	struct cn_queue_dev *pdev = cbq->pdev;
+
+	if (likely(pdev->cn_queue))
+		return queue_work(pdev->cn_queue, work);
+
+	/* Don't create the connector workqueue twice */
+	if (atomic_inc_return(&pdev->wq_requested) == 1)
+		schedule_work(&pdev->wq_creation);
+	else
+		atomic_dec(&pdev->wq_requested);
+
+	return schedule_work(work);
+}
+
 void cn_queue_wrapper(struct work_struct *work)
 {
 	struct cn_callback_entry *cbq =
@@ -58,14 +100,17 @@ static struct cn_callback_entry *cn_queue_alloc_callback_entry(char *name, struc
 	snprintf(cbq->id.name, sizeof(cbq->id.name), "%s", name);
 	memcpy(&cbq->id.id, id, sizeof(struct cb_id));
 	cbq->data.callback = callback;
-	
+
 	INIT_WORK(&cbq->work, &cn_queue_wrapper);
 	return cbq;
 }
 
 static void cn_queue_free_callback(struct cn_callback_entry *cbq)
 {
-	flush_workqueue(cbq->pdev->cn_queue);
+	/* The first jobs have been sent to kevent, flush them too */
+	flush_scheduled_work();
+	if (cbq->pdev->cn_queue)
+		flush_workqueue(cbq->pdev->cn_queue);
 
 	kfree(cbq);
 }
@@ -143,14 +188,11 @@ struct cn_queue_dev *cn_queue_alloc_dev(char *name, struct sock *nls)
 	atomic_set(&dev->refcnt, 0);
 	INIT_LIST_HEAD(&dev->queue_list);
 	spin_lock_init(&dev->queue_lock);
+	init_waitqueue_head(&dev->wq_created);
 
 	dev->nls = nls;
 
-	dev->cn_queue = create_singlethread_workqueue(dev->name);
-	if (!dev->cn_queue) {
-		kfree(dev);
-		return NULL;
-	}
+	INIT_WORK(&dev->wq_creation, cn_queue_create);
 
 	return dev;
 }
@@ -158,9 +200,25 @@ struct cn_queue_dev *cn_queue_alloc_dev(char *name, struct sock *nls)
 void cn_queue_free_dev(struct cn_queue_dev *dev)
 {
 	struct cn_callback_entry *cbq, *n;
+	long timeout;
+	DEFINE_WAIT(wait);
+
+	/* Flush the first pending jobs queued on kevent */
+	flush_scheduled_work();
+
+	/* If the connector workqueue creation is still pending, wait for it */
+	prepare_to_wait(&dev->wq_created, &wait, TASK_UNINTERRUPTIBLE);
+	if (atomic_read(&dev->wq_requested) && !dev->cn_queue) {
+		timeout = schedule_timeout(HZ * 2);
+		if (!timeout && !dev->cn_queue)
+			WARN_ON(1);
+	}
+	finish_wait(&dev->wq_created, &wait);
 
-	flush_workqueue(dev->cn_queue);
-	destroy_workqueue(dev->cn_queue);
+	if (dev->cn_queue) {
+		flush_workqueue(dev->cn_queue);
+		destroy_workqueue(dev->cn_queue);
+	}
 
 	spin_lock_bh(&dev->queue_lock);
 	list_for_each_entry_safe(cbq, n, &dev->queue_list, callback_entry)