multiqueue: Hold weak references to pads/multiqueue in SingleQueue

Without holding a ref we have no guarantees that the SingleQueue
doesn't have dangling pointers on those objects during its destruction.

plugins/elements/gstmultiqueue.c

@@ -118,10 +118,9 @@ struct _GstSingleQueue
   guint groupid;
   GstClockTimeDiff group_high_time;
 
-  GstMultiQueue *mqueue;
+  GWeakRef mqueue;
-
+  GWeakRef sinkpad;
-  GstPad *sinkpad;
+  GWeakRef srcpad;
-  GstPad *srcpad;
 
   /* flowreturn of previous srcpad push */
   GstFlowReturn srcresult;
@@ -343,10 +342,18 @@ gst_multiqueue_pad_get_property (GObject * object, guint prop_id,
 
   switch (prop_id) {
     case PROP_PAD_GROUP_ID:
-      GST_OBJECT_LOCK (pad->sq->mqueue);
+      if (pad->sq) {
-      if (pad->sq)
+        GstMultiQueue *mq = g_weak_ref_get (&pad->sq->mqueue);
+
+        if (mq)
+          GST_OBJECT_LOCK (mq);
+
         g_value_set_uint (value, pad->sq->groupid);
-      GST_OBJECT_UNLOCK (pad->sq->mqueue);
+        if (mq) {
+          GST_OBJECT_UNLOCK (mq);
+          gst_object_unref (mq);
+        }
+      }
       break;
     default:
       G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
@@ -362,10 +369,19 @@ gst_multiqueue_pad_set_property (GObject * object, guint prop_id,
 
   switch (prop_id) {
     case PROP_PAD_GROUP_ID:
-      GST_OBJECT_LOCK (pad->sq->mqueue);
+      if (pad->sq) {
-      if (pad->sq)
+        GstMultiQueue *mqueue = g_weak_ref_get (&pad->sq->mqueue);
+
+        if (mqueue)
+          GST_OBJECT_LOCK (mqueue);
+
         pad->sq->groupid = g_value_get_uint (value);
-      GST_OBJECT_UNLOCK (pad->sq->mqueue);
+
+        if (mqueue) {
+          GST_OBJECT_UNLOCK (mqueue);
+          gst_object_unref (mqueue);
+        }
+      }
       break;
     default:
       G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
@@ -900,7 +916,7 @@ static GstIterator *
 gst_multi_queue_iterate_internal_links (GstPad * pad, GstObject * parent)
 {
   GstIterator *it = NULL;
-  GstPad *opad;
+  GstPad *opad, *sinkpad, *srcpad;
   GstSingleQueue *squeue;
   GstMultiQueue *mq = GST_MULTI_QUEUE (parent);
   GValue val = { 0, };
@@ -910,12 +926,21 @@ gst_multi_queue_iterate_internal_links (GstPad * pad, GstObject * parent)
   if (!squeue)
     goto out;
 
-  if (squeue->sinkpad == pad)
+  srcpad = g_weak_ref_get (&squeue->srcpad);
-    opad = gst_object_ref (squeue->srcpad);
+  sinkpad = g_weak_ref_get (&squeue->sinkpad);
-  else if (squeue->srcpad == pad)
+  if (sinkpad == pad) {
-    opad = gst_object_ref (squeue->sinkpad);
+    opad = srcpad;
-  else
+    gst_clear_object (&sinkpad);
+
+  } else if (srcpad == pad) {
+    opad = sinkpad;
+    gst_clear_object (&srcpad);
+
+  } else {
+    gst_clear_object (&srcpad);
+    gst_clear_object (&sinkpad);
     goto out;
+  }
 
   g_value_init (&val, GST_TYPE_PAD);
   g_value_set_object (&val, opad);
@@ -952,7 +977,10 @@ gst_multi_queue_request_new_pad (GstElement * element, GstPadTemplate * temp,
   /* Create a new single queue, add the sink and source pad and return the sink pad */
   squeue = gst_single_queue_new (mqueue, temp_id);
 
-  new_pad = squeue ? squeue->sinkpad : NULL;
+  new_pad = squeue ? g_weak_ref_get (&squeue->sinkpad) : NULL;
+  /* request pad assumes the element is owning the ref of the pad it returns */
+  if (new_pad)
+    gst_object_unref (new_pad);
 
   GST_DEBUG_OBJECT (mqueue, "Returning pad %" GST_PTR_FORMAT, new_pad);
 
@@ -962,6 +990,7 @@ gst_multi_queue_request_new_pad (GstElement * element, GstPadTemplate * temp,
 static void
 gst_multi_queue_release_pad (GstElement * element, GstPad * pad)
 {
+  GstPad *sinkpad = NULL, *srcpad = NULL;
   GstMultiQueue *mqueue = GST_MULTI_QUEUE (element);
   GstSingleQueue *sq = NULL;
   GList *tmp;
@@ -972,12 +1001,19 @@ gst_multi_queue_release_pad (GstElement * element, GstPad * pad)
   /* Find which single queue it belongs to, knowing that it should be a sinkpad */
   for (tmp = mqueue->queues; tmp; tmp = g_list_next (tmp)) {
     sq = (GstSingleQueue *) tmp->data;
+    sinkpad = g_weak_ref_get (&sq->sinkpad);
 
-    if (sq->sinkpad == pad)
+    if (sinkpad == pad) {
+      srcpad = g_weak_ref_get (&sq->srcpad);
       break;
+    }
+
+    gst_object_unref (sinkpad);
   }
 
   if (!tmp) {
+    gst_clear_object (&sinkpad);
+    gst_clear_object (&srcpad);
     GST_WARNING_OBJECT (mqueue, "That pad doesn't belong to this element ???");
     GST_MULTI_QUEUE_MUTEX_UNLOCK (mqueue);
     return;
@@ -996,10 +1032,12 @@ gst_multi_queue_release_pad (GstElement * element, GstPad * pad)
   /* delete SingleQueue */
   gst_data_queue_set_flushing (sq->queue, TRUE);
 
-  gst_pad_set_active (sq->srcpad, FALSE);
+  gst_pad_set_active (srcpad, FALSE);
-  gst_pad_set_active (sq->sinkpad, FALSE);
+  gst_pad_set_active (sinkpad, FALSE);
-  gst_element_remove_pad (element, sq->srcpad);
+  gst_element_remove_pad (element, srcpad);
-  gst_element_remove_pad (element, sq->sinkpad);
+  gst_element_remove_pad (element, sinkpad);
+  gst_object_unref (srcpad);
+  gst_object_unref (sinkpad);
 }
 
 static GstStateChangeReturn
@@ -1061,18 +1099,32 @@ gst_multi_queue_change_state (GstElement * element, GstStateChange transition)
 static gboolean
 gst_single_queue_start (GstMultiQueue * mq, GstSingleQueue * sq)
 {
+  gboolean res = FALSE;
+  GstPad *srcpad = g_weak_ref_get (&sq->srcpad);
+
   GST_LOG_OBJECT (mq, "SingleQueue %d : starting task", sq->id);
-  return gst_pad_start_task (sq->srcpad,
+
-      (GstTaskFunction) gst_multi_queue_loop, sq->srcpad, NULL);
+  if (srcpad) {
+    res = gst_pad_start_task (srcpad,
+        (GstTaskFunction) gst_multi_queue_loop, srcpad, NULL);
+    gst_object_unref (srcpad);
+  }
+
+  return res;
 }
 
 static gboolean
 gst_single_queue_pause (GstMultiQueue * mq, GstSingleQueue * sq)
 {
-  gboolean result;
+  gboolean result = FALSE;
+  GstPad *srcpad = g_weak_ref_get (&sq->srcpad);
 
   GST_LOG_OBJECT (mq, "SingleQueue %d : pausing task", sq->id);
-  result = gst_pad_pause_task (sq->srcpad);
+  if (srcpad) {
+    result = gst_pad_pause_task (srcpad);
+    gst_object_unref (srcpad);
+  }
+
   sq->sink_tainted = sq->src_tainted = TRUE;
   return result;
 }
@@ -1080,10 +1132,14 @@ gst_single_queue_pause (GstMultiQueue * mq, GstSingleQueue * sq)
 static gboolean
 gst_single_queue_stop (GstMultiQueue * mq, GstSingleQueue * sq)
 {
-  gboolean result;
+  gboolean result = FALSE;
+  GstPad *srcpad = g_weak_ref_get (&sq->srcpad);
 
   GST_LOG_OBJECT (mq, "SingleQueue %d : stopping task", sq->id);
-  result = gst_pad_stop_task (sq->srcpad);
+  if (srcpad) {
+    result = gst_pad_stop_task (srcpad);
+    gst_object_unref (srcpad);
+  }
   sq->sink_tainted = sq->src_tainted = TRUE;
   return result;
 }
@@ -1145,14 +1201,14 @@ gst_single_queue_flush (GstMultiQueue * mq, GstSingleQueue * sq, gboolean flush,
 
 /* WITH LOCK TAKEN */
 static gint
-get_buffering_level (GstSingleQueue * sq)
+get_buffering_level (GstMultiQueue * mq, GstSingleQueue * sq)
 {
   GstDataQueueSize size;
   gint buffering_level, tmp;
 
   gst_data_queue_get_level (sq->queue, &size);
 
-  GST_DEBUG_OBJECT (sq->mqueue,
+  GST_DEBUG_OBJECT (mq,
       "queue %d: visible %u/%u, bytes %u/%u, time %" G_GUINT64_FORMAT "/%"
       G_GUINT64_FORMAT, sq->id, size.visible, sq->max_size.visible,
       size.bytes, sq->max_size.bytes, sq->cur_time, sq->max_size.time);
@@ -1190,7 +1246,7 @@ update_buffering (GstMultiQueue * mq, GstSingleQueue * sq)
   if (!mq->use_buffering)
     return;
 
-  buffering_level = get_buffering_level (sq);
+  buffering_level = get_buffering_level (mq, sq);
 
   /* scale so that if buffering_level equals the high watermark,
    * the percentage is 100% */
@@ -1214,7 +1270,7 @@ update_buffering (GstMultiQueue * mq, GstSingleQueue * sq)
     for (iter = mq->queues; iter; iter = g_list_next (iter)) {
       GstSingleQueue *oq = (GstSingleQueue *) iter->data;
 
-      if (get_buffering_level (oq) >= mq->high_watermark) {
+      if (get_buffering_level (mq, oq) >= mq->high_watermark) {
         is_buffering = FALSE;
 
         break;
@@ -1624,6 +1680,13 @@ gst_single_queue_push_one (GstMultiQueue * mq, GstSingleQueue * sq,
     GstMiniObject * object, gboolean * allow_drop)
 {
   GstFlowReturn result = sq->srcresult;
+  GstPad *srcpad = g_weak_ref_get (&sq->srcpad);
+
+  if (!srcpad) {
+    GST_INFO_OBJECT (mq,
+        "Pushing while corresponding sourcepad has been cleared");
+    return GST_FLOW_FLUSHING;
+  }
 
   if (GST_IS_BUFFER (object)) {
     GstBuffer *buffer;
@@ -1647,7 +1710,7 @@ gst_single_queue_push_one (GstMultiQueue * mq, GstSingleQueue * sq,
       GST_DEBUG_OBJECT (mq,
           "SingleQueue %d : Pushing buffer %p with ts %" GST_TIME_FORMAT,
           sq->id, buffer, GST_TIME_ARGS (timestamp));
-      result = gst_pad_push (sq->srcpad, buffer);
+      result = gst_pad_push (srcpad, buffer);
     }
   } else if (GST_IS_EVENT (object)) {
     GstEvent *event;
@@ -1696,7 +1759,7 @@ gst_single_queue_push_one (GstMultiQueue * mq, GstSingleQueue * sq,
           "SingleQueue %d : Pushing event %p of type %s",
           sq->id, event, GST_EVENT_TYPE_NAME (event));
 
-      gst_pad_push_event (sq->srcpad, event);
+      gst_pad_push_event (srcpad, event);
     }
   } else if (GST_IS_QUERY (object)) {
     GstQuery *query;
@@ -1710,7 +1773,7 @@ gst_single_queue_push_one (GstMultiQueue * mq, GstSingleQueue * sq,
       gst_query_unref (query);
       res = FALSE;
     } else {
-      res = gst_pad_peer_query (sq->srcpad, query);
+      res = gst_pad_peer_query (srcpad, query);
     }
 
     GST_MULTI_QUEUE_MUTEX_LOCK (mq);
@@ -1722,6 +1785,8 @@ gst_single_queue_push_one (GstMultiQueue * mq, GstSingleQueue * sq,
     g_warning ("Unexpected object in singlequeue %u (refcounting problem?)",
         sq->id);
   }
+
+  gst_object_unref (srcpad);
   return result;
 
   /* ERRORS */
@@ -1801,9 +1866,14 @@ gst_multi_queue_loop (GstPad * pad)
   gboolean is_buffer;
   gboolean do_update_buffering = FALSE;
   gboolean dropping = FALSE;
+  GstPad *srcpad = NULL;
 
   sq = GST_MULTIQUEUE_PAD (pad)->sq;
-  mq = sq->mqueue;
+  mq = g_weak_ref_get (&sq->mqueue);
+  srcpad = g_weak_ref_get (&sq->srcpad);
+
+  if (!mq || !srcpad)
+    goto out_flushing;
 
 next:
   GST_DEBUG_OBJECT (mq, "SingleQueue %d : trying to pop an object", sq->id);
@@ -2037,11 +2107,11 @@ next:
   gst_multi_queue_post_buffering (mq);
 
   GST_LOG_OBJECT (mq, "sq:%d AFTER PUSHING sq->srcresult: %s (is_eos:%d)",
-      sq->id, gst_flow_get_name (sq->srcresult), GST_PAD_IS_EOS (sq->srcpad));
+      sq->id, gst_flow_get_name (sq->srcresult), GST_PAD_IS_EOS (srcpad));
 
   /* Need to make sure wake up any sleeping pads when we exit */
   GST_MULTI_QUEUE_MUTEX_LOCK (mq);
-  if (mq->numwaiting > 0 && (GST_PAD_IS_EOS (sq->srcpad)
+  if (mq->numwaiting > 0 && (GST_PAD_IS_EOS (srcpad)
           || sq->srcresult == GST_FLOW_EOS)) {
     compute_high_time (mq, sq->groupid);
     compute_high_id (mq);
@@ -2056,6 +2126,10 @@ next:
       && result != GST_FLOW_EOS)
     goto out_flushing;
 
+done:
+  gst_clear_object (&mq);
+  gst_clear_object (&srcpad);
+
   return;
 
 out_flushing:
@@ -2086,11 +2160,11 @@ out_flushing:
     gst_single_queue_flush_queue (sq, FALSE);
     single_queue_underrun_cb (sq->queue, sq);
     gst_data_queue_set_flushing (sq->queue, TRUE);
-    gst_pad_pause_task (sq->srcpad);
+    gst_pad_pause_task (srcpad);
     GST_CAT_LOG_OBJECT (multi_queue_debug, mq,
         "SingleQueue[%d] task paused, reason:%s",
         sq->id, gst_flow_get_name (sq->srcresult));
-    return;
+    goto done;
   }
 }
 
@@ -2106,12 +2180,15 @@ gst_multi_queue_chain (GstPad * pad, GstObject * parent, GstBuffer * buffer)
 {
   GstSingleQueue *sq;
   GstMultiQueue *mq;
-  GstMultiQueueItem *item;
+  GstMultiQueueItem *item = NULL;
   guint32 curid;
   GstClockTime timestamp, duration;
 
   sq = GST_MULTIQUEUE_PAD (pad)->sq;
-  mq = sq->mqueue;
+  mq = g_weak_ref_get (&sq->mqueue);
+
+  if (!mq)
+    goto flushing;
 
   /* if eos, we are always full, so avoid hanging incoming indefinitely */
   if (sq->is_eos)
@@ -2164,6 +2241,7 @@ gst_multi_queue_chain (GstPad * pad, GstObject * parent, GstBuffer * buffer)
   apply_buffer (mq, sq, timestamp, duration, &sq->sink_segment);
 
 done:
+  gst_clear_object (&mq);
   return sq->srcresult;
 
   /* ERRORS */
@@ -2171,13 +2249,15 @@ flushing:
   {
     GST_LOG_OBJECT (mq, "SingleQueue %d : exit because task paused, reason: %s",
         sq->id, gst_flow_get_name (sq->srcresult));
-    gst_multi_queue_item_destroy (item);
+    if (item)
+      gst_multi_queue_item_destroy (item);
     goto done;
   }
 was_eos:
   {
     GST_DEBUG_OBJECT (mq, "we are EOS, dropping buffer, return EOS");
     gst_buffer_unref (buffer);
+    gst_object_unref (mq);
     return GST_FLOW_EOS;
   }
 }
@@ -2250,9 +2330,19 @@ gst_multi_queue_sink_event (GstPad * pad, GstObject * parent, GstEvent * event)
   GstFlowReturn flowret = GST_FLOW_OK;
   GstEventType type;
   GstEvent *sref = NULL;
+  GstPad *srcpad;
+
 
   sq = GST_MULTIQUEUE_PAD (pad)->sq;
   mq = (GstMultiQueue *) parent;
+  srcpad = g_weak_ref_get (&sq->srcpad);
+
+  if (!srcpad) {
+    GST_INFO_OBJECT (pad, "Pushing while corresponding sourcepad has been"
+        " removed already");
+
+    return GST_FLOW_FLUSHING;
+  }
 
   type = GST_EVENT_TYPE (event);
 
@@ -2278,7 +2368,7 @@ gst_multi_queue_sink_event (GstPad * pad, GstObject * parent, GstEvent * event)
       GST_DEBUG_OBJECT (mq, "SingleQueue %d : received flush start event",
           sq->id);
 
-      res = gst_pad_push_event (sq->srcpad, event);
+      res = gst_pad_push_event (srcpad, event);
 
       gst_single_queue_flush (mq, sq, TRUE, FALSE);
       gst_single_queue_pause (mq, sq);
@@ -2288,7 +2378,7 @@ gst_multi_queue_sink_event (GstPad * pad, GstObject * parent, GstEvent * event)
       GST_DEBUG_OBJECT (mq, "SingleQueue %d : received flush stop event",
           sq->id);
 
-      res = gst_pad_push_event (sq->srcpad, event);
+      res = gst_pad_push_event (srcpad, event);
 
       gst_single_queue_flush (mq, sq, FALSE, FALSE);
       gst_single_queue_start (mq, sq);
@@ -2322,7 +2412,7 @@ gst_multi_queue_sink_event (GstPad * pad, GstObject * parent, GstEvent * event)
 
     default:
       if (!(GST_EVENT_IS_SERIALIZED (event))) {
-        res = gst_pad_push_event (sq->srcpad, event);
+        res = gst_pad_push_event (srcpad, event);
         goto done;
       }
       break;
@@ -2396,6 +2486,8 @@ gst_multi_queue_sink_event (GstPad * pad, GstObject * parent, GstEvent * event)
   }
 
 done:
+
+  gst_object_unref (srcpad);
   if (res == FALSE)
     flowret = GST_FLOW_ERROR;
   GST_DEBUG_OBJECT (mq, "SingleQueue %d : returning %s", sq->id,
@@ -2404,6 +2496,7 @@ done:
 
 flushing:
   {
+    gst_object_unref (srcpad);
     GST_LOG_OBJECT (mq, "SingleQueue %d : exit because task paused, reason: %s",
         sq->id, gst_flow_get_name (sq->srcresult));
     if (sref)
@@ -2413,6 +2506,7 @@ flushing:
   }
 was_eos:
   {
+    gst_object_unref (srcpad);
     GST_DEBUG_OBJECT (mq, "we are EOS, dropping event, return GST_FLOW_EOS");
     gst_event_unref (event);
     return GST_FLOW_EOS;
@@ -2502,7 +2596,13 @@ gst_multi_queue_src_activate_mode (GstPad * pad, GstObject * parent,
   gboolean result;
 
   sq = GST_MULTIQUEUE_PAD (pad)->sq;
-  mq = sq->mqueue;
+  mq = g_weak_ref_get (&sq->mqueue);
+
+  if (!mq) {
+    GST_ERROR_OBJECT (pad, "No multique set anymore, can't activate pad");
+
+    return FALSE;
+  }
 
   GST_DEBUG_OBJECT (mq, "SingleQueue %d", sq->id);
 
@@ -2520,6 +2620,7 @@ gst_multi_queue_src_activate_mode (GstPad * pad, GstObject * parent,
       result = FALSE;
       break;
   }
+  gst_object_unref (mq);
   return result;
 }
 
@@ -2527,8 +2628,17 @@ static gboolean
 gst_multi_queue_src_event (GstPad * pad, GstObject * parent, GstEvent * event)
 {
   GstSingleQueue *sq = GST_MULTIQUEUE_PAD (pad)->sq;
-  GstMultiQueue *mq = sq->mqueue;
+  GstMultiQueue *mq = g_weak_ref_get (&sq->mqueue);
   gboolean ret;
+  GstPad *sinkpad = g_weak_ref_get (&sq->sinkpad);
+
+  if (!mq || !sinkpad) {
+    gst_clear_object (&sinkpad);
+    gst_clear_object (&mq);
+    GST_INFO_OBJECT (pad, "No multique/sinkpad set anymore, flushing");
+
+    return FALSE;
+  }
 
   switch (GST_EVENT_TYPE (event)) {
     case GST_EVENT_RECONFIGURE:
@@ -2539,13 +2649,16 @@ gst_multi_queue_src_event (GstPad * pad, GstObject * parent, GstEvent * event)
       }
       GST_MULTI_QUEUE_MUTEX_UNLOCK (mq);
 
-      ret = gst_pad_push_event (sq->sinkpad, event);
+      ret = gst_pad_push_event (sinkpad, event);
       break;
     default:
-      ret = gst_pad_push_event (sq->sinkpad, event);
+      ret = gst_pad_push_event (sinkpad, event);
       break;
   }
 
+  gst_object_unref (sinkpad);
+  gst_object_unref (mq);
+
   return ret;
 }
 
@@ -2623,6 +2736,14 @@ compute_high_id (GstMultiQueue * mq)
 
   for (tmp = mq->queues; tmp; tmp = g_list_next (tmp)) {
     GstSingleQueue *sq = (GstSingleQueue *) tmp->data;
+    GstPad *srcpad = g_weak_ref_get (&sq->srcpad);
+
+    if (!srcpad) {
+      GST_INFO_OBJECT (mq,
+          "srcpad has been removed already... ignoring single queue");
+
+      continue;
+    }
 
     GST_LOG_OBJECT (mq, "inspecting sq:%d , nextid:%d, oldid:%d, srcresult:%s",
         sq->id, sq->nextid, sq->oldid, gst_flow_get_name (sq->srcresult));
@@ -2631,18 +2752,20 @@ compute_high_id (GstMultiQueue * mq)
       /* No need to consider queues which are not waiting */
       if (sq->nextid == 0) {
         GST_LOG_OBJECT (mq, "sq:%d is not waiting - ignoring", sq->id);
+        gst_object_unref (srcpad);
         continue;
       }
 
       if (sq->nextid < lowest)
         lowest = sq->nextid;
-    } else if (!GST_PAD_IS_EOS (sq->srcpad) && sq->srcresult != GST_FLOW_EOS) {
+    } else if (!GST_PAD_IS_EOS (srcpad) && sq->srcresult != GST_FLOW_EOS) {
       /* If we don't have a global highid, or the global highid is lower than
        * this single queue's last outputted id, store the queue's one,
        * unless the singlequeue output is at EOS */
       if ((highid == G_MAXUINT32) || (sq->oldid > highid))
         highid = sq->oldid;
     }
+    gst_object_unref (srcpad);
   }
 
   if (highid == G_MAXUINT32 || lowest < highid)
@@ -2676,6 +2799,14 @@ compute_high_time (GstMultiQueue * mq, guint groupid)
 
   for (tmp = mq->queues; tmp; tmp = tmp->next) {
     GstSingleQueue *sq = (GstSingleQueue *) tmp->data;
+    GstPad *srcpad = g_weak_ref_get (&sq->srcpad);
+
+    if (!srcpad) {
+      GST_INFO_OBJECT (mq,
+          "srcpad has been removed already... ignoring single queue");
+
+      continue;
+    }
 
     GST_LOG_OBJECT (mq,
         "inspecting sq:%d (group:%d) , next_time:%" GST_STIME_FORMAT
@@ -2690,6 +2821,7 @@ compute_high_time (GstMultiQueue * mq, guint groupid)
       /* No need to consider queues which are not waiting */
       if (!GST_CLOCK_STIME_IS_VALID (sq->next_time)) {
         GST_LOG_OBJECT (mq, "sq:%d is not waiting - ignoring", sq->id);
+        gst_object_unref (srcpad);
         continue;
       }
 
@@ -2698,7 +2830,7 @@ compute_high_time (GstMultiQueue * mq, guint groupid)
       if (sq->groupid == groupid && (group_low == GST_CLOCK_STIME_NONE
               || sq->next_time < group_low))
         group_low = sq->next_time;
-    } else if (!GST_PAD_IS_EOS (sq->srcpad) && sq->srcresult != GST_FLOW_EOS) {
+    } else if (!GST_PAD_IS_EOS (srcpad) && sq->srcresult != GST_FLOW_EOS) {
       /* If we don't have a global high time, or the global high time
        * is lower than this single queue's last outputted time, store
        * the queue's one, unless the singlequeue output is at EOS. */
@@ -2717,6 +2849,8 @@ compute_high_time (GstMultiQueue * mq, guint groupid)
       GST_LOG_OBJECT (mq,
           "grouphigh %" GST_STIME_FORMAT " grouplow %" GST_STIME_FORMAT,
           GST_STIME_ARGS (group_high), GST_STIME_ARGS (group_low));
+
+    gst_object_unref (srcpad);
   }
 
   if (highest == GST_CLOCK_STIME_NONE)
@@ -2755,11 +2889,17 @@ compute_high_time (GstMultiQueue * mq, guint groupid)
 static void
 single_queue_overrun_cb (GstDataQueue * dq, GstSingleQueue * sq)
 {
-  GstMultiQueue *mq = sq->mqueue;
   GList *tmp;
   GstDataQueueSize size;
   gboolean filled = TRUE;
   gboolean empty_found = FALSE;
+  GstMultiQueue *mq = g_weak_ref_get (&sq->mqueue);
+
+  if (!mq) {
+    GST_ERROR ("No multique set anymore, not doing anything");
+
+    return;
+  }
 
   gst_data_queue_get_level (sq->queue, &size);
 
@@ -2812,6 +2952,7 @@ single_queue_overrun_cb (GstDataQueue * dq, GstSingleQueue * sq)
 
 done:
   GST_MULTI_QUEUE_MUTEX_UNLOCK (mq);
+  gst_object_unref (mq);
 
   /* Overrun is always forwarded, since this is blocking the upstream element */
   if (filled) {
@@ -2824,11 +2965,18 @@ static void
 single_queue_underrun_cb (GstDataQueue * dq, GstSingleQueue * sq)
 {
   gboolean empty = TRUE;
-  GstMultiQueue *mq = sq->mqueue;
+  GstMultiQueue *mq = g_weak_ref_get (&sq->mqueue);
   GList *tmp;
 
+  if (!mq) {
+    GST_ERROR ("No multique set anymore, not doing anything");
+
+    return;
+  }
+
   if (sq->srcresult == GST_FLOW_NOT_LINKED) {
     GST_LOG_OBJECT (mq, "Single Queue %d is empty but not-linked", sq->id);
+    gst_object_unref (mq);
     return;
   } else {
     GST_LOG_OBJECT (mq,
@@ -2855,6 +3003,7 @@ single_queue_underrun_cb (GstDataQueue * dq, GstSingleQueue * sq)
       empty = FALSE;
   }
   GST_MULTI_QUEUE_MUTEX_UNLOCK (mq);
+  gst_object_unref (mq);
 
   if (empty) {
     GST_DEBUG_OBJECT (mq, "All queues are empty, signalling it");
@@ -2867,7 +3016,13 @@ single_queue_check_full (GstDataQueue * dataq, guint visible, guint bytes,
     guint64 time, GstSingleQueue * sq)
 {
   gboolean res;
-  GstMultiQueue *mq = sq->mqueue;
+  GstMultiQueue *mq = g_weak_ref_get (&sq->mqueue);
+
+  if (!mq) {
+    GST_ERROR ("No multique set anymore, let's say we are full");
+
+    return TRUE;
+  }
 
   GST_DEBUG_OBJECT (mq,
       "queue %d: visible %u/%u, bytes %u/%u, time %" G_GUINT64_FORMAT "/%"
@@ -2875,12 +3030,16 @@ single_queue_check_full (GstDataQueue * dataq, guint visible, guint bytes,
       sq->max_size.bytes, sq->cur_time, sq->max_size.time);
 
   /* we are always filled on EOS */
-  if (sq->is_eos || sq->is_segment_done)
+  if (sq->is_eos || sq->is_segment_done) {
-    return TRUE;
+    res = TRUE;
+    goto done;
+  }
 
   /* we never go past the max visible items unless we are in buffering mode */
-  if (!mq->use_buffering && IS_FILLED (sq, visible, visible))
+  if (!mq->use_buffering && IS_FILLED (sq, visible, visible)) {
-    return TRUE;
+    res = TRUE;
+    goto done;
+  }
 
   /* check time or bytes */
   res = IS_FILLED (sq, bytes, bytes);
@@ -2896,6 +3055,8 @@ single_queue_check_full (GstDataQueue * dataq, guint visible, guint bytes,
     } else
       res |= IS_FILLED (sq, time, sq->cur_time);
   }
+done:
+  gst_object_unref (mq);
 
   return res;
 }
@@ -2906,6 +3067,8 @@ gst_single_queue_flush_queue (GstSingleQueue * sq, gboolean full)
   GstDataQueueItem *sitem;
   GstMultiQueueItem *mitem;
   gboolean was_flushing = FALSE;
+  GstPad *srcpad = g_weak_ref_get (&sq->srcpad);
+  GstMultiQueue *mq = g_weak_ref_get (&sq->mqueue);
 
   while (!gst_data_queue_is_empty (sq->queue)) {
     GstMiniObject *data;
@@ -2925,23 +3088,27 @@ gst_single_queue_flush_queue (GstSingleQueue * sq, gboolean full)
     data = sitem->object;
 
     if (!full && !mitem->is_query && GST_IS_EVENT (data)
-        && GST_EVENT_IS_STICKY (data)
+        && srcpad && GST_EVENT_IS_STICKY (data)
         && GST_EVENT_TYPE (data) != GST_EVENT_SEGMENT
         && GST_EVENT_TYPE (data) != GST_EVENT_EOS) {
-      gst_pad_store_sticky_event (sq->srcpad, GST_EVENT_CAST (data));
+      gst_pad_store_sticky_event (srcpad, GST_EVENT_CAST (data));
     }
 
     sitem->destroy (sitem);
   }
+  gst_clear_object (&srcpad);
 
   gst_data_queue_flush (sq->queue);
   if (was_flushing)
     gst_data_queue_set_flushing (sq->queue, TRUE);
 
-  GST_MULTI_QUEUE_MUTEX_LOCK (sq->mqueue);
+  if (mq) {
-  update_buffering (sq->mqueue, sq);
+    GST_MULTI_QUEUE_MUTEX_LOCK (mq);
-  GST_MULTI_QUEUE_MUTEX_UNLOCK (sq->mqueue);
+    update_buffering (mq, sq);
-  gst_multi_queue_post_buffering (sq->mqueue);
+    GST_MULTI_QUEUE_MUTEX_UNLOCK (mq);
+    gst_multi_queue_post_buffering (mq);
+    gst_object_unref (mq);
+  }
 }
 
 static void
@@ -2953,6 +3120,9 @@ gst_single_queue_unref (GstSingleQueue * sq)
     g_object_unref (sq->queue);
     g_cond_clear (&sq->turn);
     g_cond_clear (&sq->query_handled);
+    g_weak_ref_clear (&sq->sinkpad);
+    g_weak_ref_clear (&sq->srcpad);
+    g_weak_ref_clear (&sq->mqueue);
     g_free (sq);
   }
 }
@@ -2969,8 +3139,8 @@ gst_single_queue_ref (GstSingleQueue * squeue)
 static GstSingleQueue *
 gst_single_queue_new (GstMultiQueue * mqueue, guint id)
 {
+  GstPad *srcpad, *sinkpad;
   GstSingleQueue *sq;
-  GstMultiQueuePad *mqpad;
   GstPadTemplate *templ;
   gchar *name;
   GList *tmp;
@@ -3019,7 +3189,7 @@ gst_single_queue_new (GstMultiQueue * mqueue, guint id)
 
   GST_DEBUG_OBJECT (mqueue, "Creating GstSingleQueue id:%d", sq->id);
 
-  sq->mqueue = mqueue;
+  g_weak_ref_init (&sq->mqueue, mqueue);
   sq->srcresult = GST_FLOW_FLUSHING;
   sq->pushed = FALSE;
   sq->queue = gst_data_queue_new ((GstDataQueueCheckFullFunction)
@@ -3047,45 +3217,45 @@ gst_single_queue_new (GstMultiQueue * mqueue, guint id)
 
   name = g_strdup_printf ("sink_%u", sq->id);
   templ = gst_static_pad_template_get (&sinktemplate);
-  sq->sinkpad = g_object_new (GST_TYPE_MULTIQUEUE_PAD, "name", name,
+  sinkpad = g_object_new (GST_TYPE_MULTIQUEUE_PAD, "name", name,
       "direction", templ->direction, "template", templ, NULL);
+  g_weak_ref_init (&sq->sinkpad, sinkpad);
   gst_object_unref (templ);
   g_free (name);
 
-  mqpad = (GstMultiQueuePad *) sq->sinkpad;
+  GST_MULTIQUEUE_PAD (sinkpad)->sq = sq;
-  mqpad->sq = sq;
 
-  gst_pad_set_chain_function (sq->sinkpad,
+  gst_pad_set_chain_function (sinkpad,
       GST_DEBUG_FUNCPTR (gst_multi_queue_chain));
-  gst_pad_set_activatemode_function (sq->sinkpad,
+  gst_pad_set_activatemode_function (sinkpad,
       GST_DEBUG_FUNCPTR (gst_multi_queue_sink_activate_mode));
-  gst_pad_set_event_full_function (sq->sinkpad,
+  gst_pad_set_event_full_function (sinkpad,
       GST_DEBUG_FUNCPTR (gst_multi_queue_sink_event));
-  gst_pad_set_query_function (sq->sinkpad,
+  gst_pad_set_query_function (sinkpad,
       GST_DEBUG_FUNCPTR (gst_multi_queue_sink_query));
-  gst_pad_set_iterate_internal_links_function (sq->sinkpad,
+  gst_pad_set_iterate_internal_links_function (sinkpad,
       GST_DEBUG_FUNCPTR (gst_multi_queue_iterate_internal_links));
-  GST_OBJECT_FLAG_SET (sq->sinkpad, GST_PAD_FLAG_PROXY_CAPS);
+  GST_OBJECT_FLAG_SET (sinkpad, GST_PAD_FLAG_PROXY_CAPS);
 
   name = g_strdup_printf ("src_%u", sq->id);
   templ = gst_static_pad_template_get (&srctemplate);
-  sq->srcpad = g_object_new (GST_TYPE_MULTIQUEUE_PAD, "name", name,
+  srcpad = g_object_new (GST_TYPE_MULTIQUEUE_PAD, "name", name,
       "direction", templ->direction, "template", templ, NULL);
+  g_weak_ref_init (&sq->srcpad, srcpad);
   gst_object_unref (templ);
   g_free (name);
 
-  mqpad = (GstMultiQueuePad *) sq->srcpad;
+  GST_MULTIQUEUE_PAD (srcpad)->sq = gst_single_queue_ref (sq);
-  mqpad->sq = gst_single_queue_ref (sq);
 
-  gst_pad_set_activatemode_function (sq->srcpad,
+  gst_pad_set_activatemode_function (srcpad,
       GST_DEBUG_FUNCPTR (gst_multi_queue_src_activate_mode));
-  gst_pad_set_event_function (sq->srcpad,
+  gst_pad_set_event_function (srcpad,
       GST_DEBUG_FUNCPTR (gst_multi_queue_src_event));
-  gst_pad_set_query_function (sq->srcpad,
+  gst_pad_set_query_function (srcpad,
       GST_DEBUG_FUNCPTR (gst_multi_queue_src_query));
-  gst_pad_set_iterate_internal_links_function (sq->srcpad,
+  gst_pad_set_iterate_internal_links_function (srcpad,
       GST_DEBUG_FUNCPTR (gst_multi_queue_iterate_internal_links));
-  GST_OBJECT_FLAG_SET (sq->srcpad, GST_PAD_FLAG_PROXY_CAPS);
+  GST_OBJECT_FLAG_SET (srcpad, GST_PAD_FLAG_PROXY_CAPS);
 
   GST_MULTI_QUEUE_MUTEX_UNLOCK (mqueue);
 
@@ -3094,11 +3264,11 @@ gst_single_queue_new (GstMultiQueue * mqueue, guint id)
    * between activating and adding */
   g_rec_mutex_lock (GST_STATE_GET_LOCK (mqueue));
   if (GST_STATE_TARGET (mqueue) != GST_STATE_NULL) {
-    gst_pad_set_active (sq->srcpad, TRUE);
+    gst_pad_set_active (srcpad, TRUE);
-    gst_pad_set_active (sq->sinkpad, TRUE);
+    gst_pad_set_active (sinkpad, TRUE);
   }
-  gst_element_add_pad (GST_ELEMENT (mqueue), sq->srcpad);
+  gst_element_add_pad (GST_ELEMENT (mqueue), srcpad);
-  gst_element_add_pad (GST_ELEMENT (mqueue), sq->sinkpad);
+  gst_element_add_pad (GST_ELEMENT (mqueue), sinkpad);
   if (GST_STATE_TARGET (mqueue) != GST_STATE_NULL) {
     gst_single_queue_start (mqueue, sq);
   }