linux-kernel - [PATCH 05/31] media: Media Controller fix to not let stream

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Date:	Wed,  6 Jan 2016 13:26:54 -0700
From:	Shuah Khan <shuahkh@....samsung.com>
To:	mchehab@....samsung.com, tiwai@...e.com, clemens@...isch.de,
	hans.verkuil@...co.com, laurent.pinchart@...asonboard.com,
	sakari.ailus@...ux.intel.com, javier@....samsung.com
Cc:	Shuah Khan <shuahkh@....samsung.com>, pawel@...iak.com,
	m.szyprowski@...sung.com, kyungmin.park@...sung.com,
	perex@...ex.cz, arnd@...db.de, dan.carpenter@...cle.com,
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	corbet@....net, chehabrafael@...il.com, k.kozlowski@...sung.com,
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	linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
	linux-api@...r.kernel.org, alsa-devel@...a-project.org
Subject: [PATCH 05/31] media: Media Controller fix to not let stream_count go negative

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@....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 6e02d19..78486a9 100644
--- a/drivers/media/media-entity.c
+++ b/drivers/media/media-entity.c
@@ -464,9 +464,12 @@ 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
@@ -498,9 +501,12 @@ 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;
+		}
 	}
 
 	if (!--pipe->streaming_count)
-- 
2.5.0

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