concat: fix locking in SEGMENT event handler

concat->current_start_offset needs the lock taken for safe access,
as it can be accessed from outside of the streaming thread, eg
in release_pad.

An early break is also added for an error case.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/818>

1 files changed, 7 insertions, 3 deletions

diff --git a/plugins/elements/gstconcat.c b/plugins/elements/gstconcat.c
index 35f43c4b03..9b732fe567 100644
--- a/plugins/elements/gstconcat.c
+++ b/plugins/elements/gstconcat.c
@@ -558,7 +558,6 @@ gst_concat_sink_event (GstPad * pad, GstObject * parent, GstEvent * event)
         self->format = spad->segment.format;
         GST_DEBUG_OBJECT (self, "Operating in %s format",
             gst_format_get_name (self->format));
-        g_mutex_unlock (&self->lock);
       } else if (self->format != spad->segment.format) {
         g_mutex_unlock (&self->lock);
         GST_ELEMENT_ERROR (self, CORE, FAILED, (NULL),
@@ -566,16 +565,19 @@ gst_concat_sink_event (GstPad * pad, GstObject * parent, GstEvent * event)
                 gst_format_get_name (self->format),
                 gst_format_get_name (spad->segment.format)));
         ret = FALSE;
-      } else {
-        g_mutex_unlock (&self->lock);
+        break;
       }
 
+      g_mutex_unlock (&self->lock);
+
       if (!gst_concat_pad_wait (spad, self)) {
         ret = FALSE;
       } else {
         GstSegment segment = spad->segment;
         GstEvent *topush;
 
+        g_mutex_lock (&self->lock);
+
         if (adjust_base) {
           /* We know no duration */
           segment.duration = -1;
@@ -609,6 +611,8 @@ gst_concat_sink_event (GstPad * pad, GstObject * parent, GstEvent * event)
         topush = gst_event_new_segment (&segment);
         gst_event_set_seqnum (topush, gst_event_get_seqnum (event));
 
+        g_mutex_unlock (&self->lock);
+
         gst_pad_push_event (self->srcpad, topush);
       }
       break;