3 files changed, 87 insertions, 20 deletions

diff --git a/drivers/connector/cn_queue.c b/drivers/connector/cn_queue.c
index b6fe7e7a2c2f..c769ef269fb5 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)
diff --git a/drivers/connector/connector.c b/drivers/connector/connector.c
index bf4830082a13..fd336c5a9057 100644
--- a/drivers/connector/connector.c
+++ b/drivers/connector/connector.c
@@ -1,9 +1,9 @@
 /*
  *      connector.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
@@ -145,14 +145,13 @@ static int cn_call_callback(struct cn_msg *msg, void (*destruct_data)(void *), v
                                 __cbq->data.ddata = data;
                                 __cbq->data.destruct_data = destruct_data;
 
-                                if (queue_work(dev->cbdev->cn_queue,
-                                                        &__cbq->work))
+                                if (queue_cn_work(__cbq, &__cbq->work))
                                         err = 0;
                                 else
                                         err = -EINVAL;
                         } else {
                                 struct cn_callback_data *d;
-                                
+
                                 err = -ENOMEM;
                                 __new_cbq = kzalloc(sizeof(struct cn_callback_entry), GFP_ATOMIC);
                                 if (__new_cbq) {
@@ -163,10 +162,12 @@ static int cn_call_callback(struct cn_msg *msg, void (*destruct_data)(void *), v
                                         d->destruct_data = destruct_data;
                                         d->free = __new_cbq;
 
+                                        __new_cbq->pdev = __cbq->pdev;
+
                                         INIT_WORK(&__new_cbq->work,
                                                         &cn_queue_wrapper);
 
-                                        if (queue_work(dev->cbdev->cn_queue,
+                                        if (queue_cn_work(__new_cbq,
                                                     &__new_cbq->work))
                                                 err = 0;
                                         else {
@@ -237,7 +238,7 @@ static void cn_notify(struct cb_id *id, u32 notify_event)
 
                 req = (struct cn_notify_req *)ctl->data;
                 for (i = 0; i < ctl->idx_notify_num; ++i, ++req) {
-                        if (id->idx >= req->first && 
+                        if (id->idx >= req->first &&
                                         id->idx < req->first + req->range) {
                                 idx_found = 1;
                                 break;
@@ -245,7 +246,7 @@ static void cn_notify(struct cb_id *id, u32 notify_event)
                 }
 
                 for (i = 0; i < ctl->val_notify_num; ++i, ++req) {
-                        if (id->val >= req->first && 
+                        if (id->val >= req->first &&
                                         id->val < req->first + req->range) {
                                 val_found = 1;
                                 break;
@@ -459,7 +460,7 @@ static int __devinit cn_init(void)
                 netlink_kernel_release(dev->nls);
                 return -EINVAL;
         }
-        
+
         cn_already_initialized = 1;
 
         err = cn_add_callback(&dev->id, "connector", &cn_callback);
diff --git a/include/linux/connector.h b/include/linux/connector.h
index 34f2789d9b9b..fc65d219d88c 100644
--- a/include/linux/connector.h
+++ b/include/linux/connector.h
@@ -109,6 +109,12 @@ struct cn_queue_dev {
         unsigned char name[CN_CBQ_NAMELEN];
 
         struct workqueue_struct *cn_queue;
+        /* Sent to kevent to create cn_queue only when needed */
+        struct work_struct wq_creation;
+        /* Tell if the wq_creation job is pending/completed */
+        atomic_t wq_requested;
+        /* Wait for cn_queue to be created */
+        wait_queue_head_t wq_created;
 
         struct list_head queue_list;
         spinlock_t queue_lock;
@@ -164,6 +170,8 @@ int cn_netlink_send(struct cn_msg *, u32, gfp_t);
 int cn_queue_add_callback(struct cn_queue_dev *dev, char *name, struct cb_id *id, void (*callback)(void *));
 void cn_queue_del_callback(struct cn_queue_dev *dev, struct cb_id *id);
 
+int queue_cn_work(struct cn_callback_entry *cbq, struct work_struct *work);
+
 struct cn_queue_dev *cn_queue_alloc_dev(char *name, struct sock *);
 void cn_queue_free_dev(struct cn_queue_dev *dev);