V4L/DVB (8701): cx18: Add missing lock for when the irq handler manipulates the queues

cx18: Add missing lock for when the irq handler manipulates the queues.  This
was a potential source of stream queue corruption.  Also changed the name of
cx18_queue_find_buf() to cx18_queue_get_buf_irq().

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

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

@@ -61,7 +61,7 @@ static void epu_dma_done(struct cx18 *cx, struct cx18_mailbox *mb)
 		CX18_WARN("Ack struct = %d for %s\n",
 			mb->args[2], s->name);
 	id = read_enc(off);
-	buf = cx18_queue_find_buf(s, id, read_enc(off + 4));
+	buf = cx18_queue_get_buf_irq(s, id, read_enc(off + 4));
 	CX18_DEBUG_HI_DMA("DMA DONE for %s (buffer %d)\n", s->name, id);
 	if (buf) {
 		cx18_buf_sync_for_cpu(s, buf);

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

@@ -78,12 +78,13 @@ struct cx18_buffer *cx18_dequeue(struct cx18_stream *s, struct cx18_queue *q)
 	return buf;
 }
 
-struct cx18_buffer *cx18_queue_find_buf(struct cx18_stream *s, u32 id,
+struct cx18_buffer *cx18_queue_get_buf_irq(struct cx18_stream *s, u32 id,
 	u32 bytesused)
 {
 	struct cx18 *cx = s->cx;
 	struct list_head *p;
 
+	spin_lock(&s->qlock);
 	list_for_each(p, &s->q_free.list) {
 		struct cx18_buffer *buf =
 			list_entry(p, struct cx18_buffer, list);
@@ -92,17 +93,19 @@ struct cx18_buffer *cx18_queue_find_buf(struct cx18_stream *s, u32 id,
 			continue;
 		buf->bytesused = bytesused;
 		/* the transport buffers are handled differently,
-		   so there is no need to move them to the full queue */
-		if (s->type == CX18_ENC_STREAM_TYPE_TS)
-			return buf;
-		s->q_free.buffers--;
-		s->q_free.length -= s->buf_size;
-		s->q_full.buffers++;
-		s->q_full.length += s->buf_size;
-		s->q_full.bytesused += buf->bytesused;
-		list_move_tail(&buf->list, &s->q_full.list);
+		   they are not moved to the full queue */
+		if (s->type != CX18_ENC_STREAM_TYPE_TS) {
+			s->q_free.buffers--;
+			s->q_free.length -= s->buf_size;
+			s->q_full.buffers++;
+			s->q_full.length += s->buf_size;
+			s->q_full.bytesused += buf->bytesused;
+			list_move_tail(&buf->list, &s->q_full.list);
+		}
+		spin_unlock(&s->qlock);
 		return buf;
 	}
+	spin_unlock(&s->qlock);
 	CX18_ERR("Cannot find buffer %d for stream %s\n", id, s->name);
 	return NULL;
 }

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

@@ -46,7 +46,7 @@ void cx18_queue_init(struct cx18_queue *q);
 void cx18_enqueue(struct cx18_stream *s, struct cx18_buffer *buf,
 	struct cx18_queue *q);
 struct cx18_buffer *cx18_dequeue(struct cx18_stream *s, struct cx18_queue *q);
-struct cx18_buffer *cx18_queue_find_buf(struct cx18_stream *s, u32 id,
+struct cx18_buffer *cx18_queue_get_buf_irq(struct cx18_stream *s, u32 id,
 	u32 bytesused);
 void cx18_flush_queues(struct cx18_stream *s);