V4L/DVB (9722): cx18: Convert per stream queue spinlocks into mutexes

Convert the per stream queue spinlocks into mutexes.  All queue
manipulation happens via the work queue or system calls into the driver, and
not in an interrupt context.  This reduces the amout of time the cx18 driver
keeps interrupts disabled.

Signed-off-by: Andy Walls <awalls@radix.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/video/cx18/cx18-driver.h

@@ -271,7 +271,7 @@ struct cx18_stream {
 	unsigned mdl_offset;
 
 	u32 id;
-	spinlock_t qlock; 	/* locks access to the queues */
+	struct mutex qlock; 	/* locks access to the queues */
 	unsigned long s_flags;	/* status flags, see above */
 	int dma;		/* can be PCI_DMA_TODEVICE,
 				   PCI_DMA_FROMDEVICE or

drivers/media/video/cx18/cx18-queue.c

@@ -44,34 +44,31 @@ void cx18_queue_init(struct cx18_queue *q)
 void cx18_enqueue(struct cx18_stream *s, struct cx18_buffer *buf,
 		struct cx18_queue *q)
 {
-	unsigned long flags = 0;
-
 	/* clear the buffer if it is going to be enqueued to the free queue */
 	if (q == &s->q_free) {
 		buf->bytesused = 0;
 		buf->readpos = 0;
 		buf->b_flags = 0;
 	}
-	spin_lock_irqsave(&s->qlock, flags);
+	mutex_lock(&s->qlock);
 	list_add_tail(&buf->list, &q->list);
 	atomic_inc(&q->buffers);
 	q->bytesused += buf->bytesused - buf->readpos;
-	spin_unlock_irqrestore(&s->qlock, flags);
+	mutex_unlock(&s->qlock);
 }
 
 struct cx18_buffer *cx18_dequeue(struct cx18_stream *s, struct cx18_queue *q)
 {
 	struct cx18_buffer *buf = NULL;
-	unsigned long flags = 0;
 
-	spin_lock_irqsave(&s->qlock, flags);
+	mutex_lock(&s->qlock);
 	if (!list_empty(&q->list)) {
 		buf = list_entry(q->list.next, struct cx18_buffer, list);
 		list_del_init(q->list.next);
 		atomic_dec(&q->buffers);
 		q->bytesused -= buf->bytesused - buf->readpos;
 	}
-	spin_unlock_irqrestore(&s->qlock, flags);
+	mutex_unlock(&s->qlock);
 	return buf;
 }
 
@@ -80,9 +77,8 @@ struct cx18_buffer *cx18_queue_get_buf(struct cx18_stream *s, u32 id,
 {
 	struct cx18 *cx = s->cx;
 	struct list_head *p;
-	unsigned long flags = 0;
 
-	spin_lock_irqsave(&s->qlock, flags);
+	mutex_lock(&s->qlock);
 	list_for_each(p, &s->q_free.list) {
 		struct cx18_buffer *buf =
 			list_entry(p, struct cx18_buffer, list);
@@ -102,32 +98,31 @@ struct cx18_buffer *cx18_queue_get_buf(struct cx18_stream *s, u32 id,
 			list_move_tail(&buf->list, &s->q_full.list);
 		}
 
-		spin_unlock_irqrestore(&s->qlock, flags);
+		mutex_unlock(&s->qlock);
 		return buf;
 	}
-	spin_unlock_irqrestore(&s->qlock, flags);
+	mutex_unlock(&s->qlock);
 	CX18_ERR("Cannot find buffer %d for stream %s\n", id, s->name);
 	return NULL;
 }
 
 /* Move all buffers of a queue to q_free, while flushing the buffers */
 static void cx18_queue_flush(struct cx18_stream *s, struct cx18_queue *q)
 {
-	unsigned long flags;
 	struct cx18_buffer *buf;
 
 	if (q == &s->q_free)
 		return;
 
-	spin_lock_irqsave(&s->qlock, flags);
+	mutex_lock(&s->qlock);
 	while (!list_empty(&q->list)) {
 		buf = list_entry(q->list.next, struct cx18_buffer, list);
 		list_move_tail(q->list.next, &s->q_free.list);
 		buf->bytesused = buf->readpos = buf->b_flags = 0;
 		atomic_inc(&s->q_free.buffers);
 	}
 	cx18_queue_init(q);
-	spin_unlock_irqrestore(&s->qlock, flags);
+	mutex_unlock(&s->qlock);
 }
 
 void cx18_flush_queues(struct cx18_stream *s)

drivers/media/video/cx18/cx18-streams.c

@@ -132,7 +132,7 @@ static void cx18_stream_init(struct cx18 *cx, int type)
 		s->buffers = 63;
 		s->buf_size = (max_size / s->buffers) & ~0xfff;
 	}
-	spin_lock_init(&s->qlock);
+	mutex_init(&s->qlock);
 	init_waitqueue_head(&s->waitq);
 	s->id = -1;
 	cx18_queue_init(&s->q_free);