nlecomposition: Ensure flushes after seek have the right seqnum

Seeks that lead to a stack change lead to deactivating the current
stack. At that point we explicitely flush downstream as a reaction to
the flushing seek. Until now those flushes had a random seqnum, this
fails if we are a nested compostion as the parent composition will end
up dropping that flush which in turns might lead to deadlocks. For
example, the flush goes through a `compositor` which wants to flush
downstream to stop its srcpad task, but that flush wouldn't have
"released" its srcpad thread if the composition srcpad drops it, meaning
it won't be able to stop the task ever.

plugins/nle/nlecomposition.c

@@ -264,7 +264,7 @@ static gboolean _nle_composition_add_object (NleComposition * comp,
 static gboolean _nle_composition_remove_object (NleComposition * comp,
     NleObject * object);
 static void _deactivate_stack (NleComposition * comp,
-    gboolean flush_downstream);
+    NleUpdateStackReason reason);
 static gboolean _set_real_eos_seqnum_from_seek (NleComposition * comp,
     GstEvent * event);
 static void _emit_commited_signal_func (NleComposition * comp, gpointer udata);
@@ -589,7 +589,8 @@ _seek_pipeline_func (NleComposition * comp, SeekData * seekd)
 
   priv->next_base_time = 0;
 
-  comp->priv->seek_seqnum = gst_event_get_seqnum (seekd->event);
+  comp->priv->flush_seqnum = comp->priv->seek_seqnum =
+      gst_event_get_seqnum (seekd->event);
   seek_handling (seekd->comp, gst_event_get_seqnum (seekd->event),
       COMP_UPDATE_STACK_ON_SEEK);
 
@@ -599,7 +600,7 @@ _seek_pipeline_func (NleComposition * comp, SeekData * seekd)
 
 /*  Must be called with OBJECTS_LOCK taken */
 static void
-_process_pending_entries (NleComposition * comp)
+_process_pending_entries (NleComposition * comp, NleUpdateStackReason reason)
 {
   NleObject *object;
   GHashTableIter iter;
@@ -615,7 +616,7 @@ _process_pending_entries (NleComposition * comp)
           deactivated_stack == FALSE) {
         deactivated_stack = TRUE;
 
-        _deactivate_stack (comp, TRUE);
+        _deactivate_stack (comp, reason);
       }
 
       _nle_composition_remove_object (comp, object);
@@ -649,13 +650,13 @@ _commit_values (NleComposition * comp)
 }
 
 static gboolean
-_commit_all_values (NleComposition * comp)
+_commit_all_values (NleComposition * comp, NleUpdateStackReason reason)
 {
   NleCompositionPrivate *priv = comp->priv;
 
   priv->next_base_time = 0;
 
-  _process_pending_entries (comp);
+  _process_pending_entries (comp, reason);
 
   if (_commit_values (comp) == FALSE) {
 
@@ -679,7 +680,7 @@ _initialize_stack_func (NleComposition * comp, UpdateCompositionData * ucompo)
 
   _post_start_composition_update (comp, ucompo->seqnum, ucompo->reason);
 
-  _commit_all_values (comp);
+  _commit_all_values (comp, ucompo->reason);
   update_start_stop_duration (comp);
   comp->priv->next_base_time = 0;
   /* set ghostpad target */
@@ -2276,7 +2277,7 @@ _drop_all_cb (GstPad * pad G_GNUC_UNUSED,
 
 /*  Must be called with OBJECTS_LOCK taken */
 static void
-_set_current_bin_to_ready (NleComposition * comp, gboolean flush_downstream)
+_set_current_bin_to_ready (NleComposition * comp, NleUpdateStackReason reason)
 {
   gint probe_id = -1;
   GstPad *ptarget = NULL;
@@ -2284,7 +2285,7 @@ _set_current_bin_to_ready (NleComposition * comp, gboolean flush_downstream)
   GstEvent *flush_event;
 
   comp->priv->tearing_down_stack = TRUE;
-  if (flush_downstream) {
+  if (_have_to_flush_downstream (reason)) {
     ptarget = gst_ghost_pad_get_target (GST_GHOST_PAD (NLE_OBJECT_SRC (comp)));
     if (ptarget) {
 
@@ -2299,7 +2300,11 @@ _set_current_bin_to_ready (NleComposition * comp, gboolean flush_downstream)
       GST_DEBUG_OBJECT (comp, "added event probe %lu", priv->ghosteventprobe);
 
       flush_event = gst_event_new_flush_start ();
-      priv->flush_seqnum = gst_event_get_seqnum (flush_event);
+      if (reason != COMP_UPDATE_STACK_ON_SEEK)
+        priv->flush_seqnum = gst_event_get_seqnum (flush_event);
+      else
+        gst_event_set_seqnum (flush_event, priv->seek_seqnum);
+
       GST_INFO_OBJECT (comp, "sending flushes downstream with seqnum %d",
           priv->flush_seqnum);
       gst_pad_push_event (ptarget, flush_event);
@@ -2312,8 +2317,9 @@ _set_current_bin_to_ready (NleComposition * comp, gboolean flush_downstream)
   gst_element_set_state (priv->current_bin, GST_STATE_READY);
 
   if (ptarget) {
-    if (flush_downstream) {
+    if (_have_to_flush_downstream (reason)) {
       flush_event = gst_event_new_flush_stop (TRUE);
+
       gst_event_set_seqnum (flush_event, priv->flush_seqnum);
 
       /* Force ad activation so that the event can actually travel.
@@ -2409,7 +2415,7 @@ _commit_func (NleComposition * comp, UpdateCompositionData * ucompo)
    * before commiting children */
   curpos = get_current_position (comp);
 
-  if (!_commit_all_values (comp)) {
+  if (!_commit_all_values (comp, ucompo->reason)) {
     GST_DEBUG_OBJECT (comp, "Nothing to commit, leaving");
 
     g_signal_emit (comp, _signals[COMMITED_SIGNAL], 0, FALSE);
@@ -2864,13 +2870,13 @@ _relink_single_node (NleComposition * comp, GNode * node,
  */
 
 static void
-_deactivate_stack (NleComposition * comp, gboolean flush_downstream)
+_deactivate_stack (NleComposition * comp, NleUpdateStackReason reason)
 {
   GstPad *ptarget;
 
-  GST_INFO_OBJECT (comp, "Deactivating current stack (flushing downstream: %d)",
+  GST_INFO_OBJECT (comp, "Deactivating current stack (reason: %s)",
-      flush_downstream);
+      UPDATE_PIPELINE_REASONS[reason]);
-  _set_current_bin_to_ready (comp, flush_downstream);
+  _set_current_bin_to_ready (comp, reason);
 
   ptarget = gst_ghost_pad_get_target (GST_GHOST_PAD (NLE_OBJECT_SRC (comp)));
   _empty_bin (GST_BIN_CAST (comp->priv->current_bin));
@@ -3196,7 +3202,7 @@ update_pipeline (NleComposition * comp, GstClockTime currenttime, gint32 seqnum,
   /* If stacks are different, unlink/relink objects */
   if (!samestack) {
     _dump_stack (comp, stack);
-    _deactivate_stack (comp, _have_to_flush_downstream (update_reason));
+    _deactivate_stack (comp, update_reason);
     _relink_new_stack (comp, stack, toplevel_seek);
   }