[alsa-devel] [PATCH MC Next Gen 04/20] media: Media Controller fix to not let stream_count go negative

[Shuah Khan]

Add a range check to not let the stream_count become negative.
Wthout this check, calls to stop pipeline when there is no active
pipeline will result in stream_count < 0 condition and lock and
preventing link state (activate/deactivate) changes. This will
happen from error leg in start pipeline interface.

Signed-off-by: Shuah Khan <shuahkh at osg.samsung.com>
---
 drivers/media/media-entity.c | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/drivers/media/media-entity.c b/drivers/media/media-entity.c
index eaeda25..797b7b3 100644
--- a/drivers/media/media-entity.c
+++ b/drivers/media/media-entity.c
@@ -502,9 +502,12 @@ error:
 	media_entity_graph_walk_start(&graph, entity_err);
 
 	while ((entity_err = media_entity_graph_walk_next(&graph))) {
-		entity_err->stream_count--;
-		if (entity_err->stream_count == 0)
-			entity_err->pipe = NULL;
+		/* don't let the stream_count go negative */
+		if (entity->stream_count > 0) {
+			entity_err->stream_count--;
+			if (entity_err->stream_count == 0)
+				entity_err->pipe = NULL;
+		}
 
 		/*
 		 * We haven't increased stream_count further than this
@@ -542,9 +545,12 @@ void media_entity_pipeline_stop(struct media_entity *entity)
 	media_entity_graph_walk_start(&graph, entity);
 
 	while ((entity = media_entity_graph_walk_next(&graph))) {
-		entity->stream_count--;
-		if (entity->stream_count == 0)
-			entity->pipe = NULL;
+		/* don't let the stream_count go negative */
+		if (entity->stream_count > 0) {
+			entity->stream_count--;
+			if (entity->stream_count == 0)
+				entity->pipe = NULL;
+		}
 	}
 
 	mutex_unlock(&mdev->graph_mutex);
-- 
2.1.4