parse: Don't hold element's object lock while querying element pads' caps

This can easily deadlock if the element uses the object lock for
something internally, like posting an error message. Use an GstIterator
for iterating over the pads instead.

https://bugzilla.gnome.org/show_bug.cgi?id=777449

diff --git a/gst/parse/grammar.y b/gst/parse/grammar.y
index 5111903..6a958c9 100644 (file)
--- a/gst/parse/grammar.y
+++ b/gst/parse/grammar.y
@@ -587,32 +587,44 @@ static gboolean
 gst_parse_element_can_do_caps (GstElement * e, GstPadDirection dir,
     GstCaps * link_caps)
 {
-  gboolean can_do = FALSE;
-  GList *pads;
+  gboolean can_do = FALSE, done = FALSE;
+  GstIterator *it;
 
-  GST_OBJECT_LOCK (e);
+  it = (dir == GST_PAD_SRC) ? gst_element_iterate_src_pads (e) : gst_element_iterate_sink_pads (e);
 
-  pads = (dir == GST_PAD_SRC) ? e->srcpads : e->sinkpads;
-
-  while (!can_do && pads != NULL) {
-    GstPad *pad = pads->data;
+  while (!done && !can_do) {
+    GValue v = G_VALUE_INIT;
+    GstPad *pad;
     GstCaps *caps;
 
-    caps = gst_pad_get_current_caps (pad);
-    if (caps == NULL)
-      caps = gst_pad_query_caps (pad, NULL);
+    switch (gst_iterator_next (it, &v)) {
+      case GST_ITERATOR_OK:
+        pad = g_value_get_object (&v);
+
+        caps = gst_pad_get_current_caps (pad);
+        if (caps == NULL)
+          caps = gst_pad_query_caps (pad, NULL);
 
-    can_do = gst_caps_can_intersect (caps, link_caps);
+        can_do = gst_caps_can_intersect (caps, link_caps);
 
-    GST_TRACE ("can_do: %d for %" GST_PTR_FORMAT " and %" GST_PTR_FORMAT,
-        can_do, caps, link_caps);
+        GST_TRACE ("can_do: %d for %" GST_PTR_FORMAT " and %" GST_PTR_FORMAT,
+            can_do, caps, link_caps);
 
-    gst_caps_unref (caps);
+        gst_caps_unref (caps);
 
-    pads = pads->next;
+        g_value_unset (&v);
+        break;
+      case GST_ITERATOR_DONE:
+      case GST_ITERATOR_ERROR:
+        done = TRUE;
+        break;
+      case GST_ITERATOR_RESYNC:
+        gst_iterator_resync (it);
+        break;
+    }
   }
 
-  GST_OBJECT_UNLOCK (e);
+  gst_iterator_free (it);
 
   return can_do;
 }