media: staging: rkisp1: params: upon stream stop, iterate a local list to return the buffers

The code in '.stop_streaming' callback releases and acquire the lock
at each iteration when returning the buffers.
Holding the lock disables interrupts so it should be minimized.
To make the code cleaner and still minimize holding the lock,
the buffer list is first moved to a local list and
then can be iterated without the lock.
Signed-off-by: Dafna Hirschfeld <dafna.hirschfeld@collabora.com>
Acked-by: Helen Koike <helen.koike@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

drivers/staging/media/rkisp1/rkisp1-params.c

@@ -1469,32 +1469,23 @@ static void rkisp1_params_vb2_stop_streaming(struct vb2_queue *vq)
 {
 	struct rkisp1_params *params = vq->drv_priv;
 	struct rkisp1_buffer *buf;
+	struct list_head tmp_list;
 	unsigned long flags;
-	unsigned int i;
 
-	/* stop params input firstly */
+	INIT_LIST_HEAD(&tmp_list);
+
+	/*
+	 * we first move the buffers into a local list 'tmp_list'
+	 * and then we can iterate it and call vb2_buffer_done
+	 * without holding the lock
+	 */
 	spin_lock_irqsave(&params->config_lock, flags);
 	params->is_streaming = false;
+	list_cut_position(&tmp_list, &params->params, params->params.prev);
 	spin_unlock_irqrestore(&params->config_lock, flags);
 
-	for (i = 0; i < RKISP1_ISP_PARAMS_REQ_BUFS_MAX; i++) {
-		spin_lock_irqsave(&params->config_lock, flags);
-		if (!list_empty(&params->params)) {
-			buf = list_first_entry(&params->params,
-					       struct rkisp1_buffer, queue);
-			list_del(&buf->queue);
-			spin_unlock_irqrestore(&params->config_lock,
-					       flags);
-		} else {
-			spin_unlock_irqrestore(&params->config_lock,
-					       flags);
-			break;
-		}
-
-		if (buf)
-			vb2_buffer_done(&buf->vb.vb2_buf, VB2_BUF_STATE_ERROR);
-		buf = NULL;
-	}
+	list_for_each_entry(buf, &tmp_list, queue)
+		vb2_buffer_done(&buf->vb.vb2_buf, VB2_BUF_STATE_ERROR);
 }
 
 static int