[Spice-devel] [client] streaming: Fix a race condition in the GStreamer frame display queue

[Francois Gouget]

When a frame is late we schedule its display right away with
g_timeout_add(0, ...). This can result in display_frame() being called
before g_timeout_add() returns. This would cause the timer_id being
reset before schedule_frame() had set it so that it would then never be
reset. So from that point schedule_frame() would always think a frame
was being displayed and thus would not schedule any more frames
resulting in a video freeze.
display_frame() now takes the queues mutex before resetting timer_id
eliminating the race.

Signed-off-by: Francois Gouget <fgouget at codeweavers.com>
---
 src/channel-display-gst.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/src/channel-display-gst.c b/src/channel-display-gst.c
index 2b4ef7f9..8be95997 100644
--- a/src/channel-display-gst.c
+++ b/src/channel-display-gst.c
@@ -127,9 +127,8 @@ static gboolean display_frame(gpointer video_decoder)
     GstBuffer *buffer;
     GstMapInfo mapinfo;
 
-    decoder->timer_id = 0;
-
     g_mutex_lock(&decoder->queues_mutex);
+    decoder->timer_id = 0;
     frame = g_queue_pop_head(decoder->display_queue);
     g_mutex_unlock(&decoder->queues_mutex);
     /* If the queue is empty we don't even need to reschedule */
-- 
2.11.0