adder: Make sure FLUSH_STOP is always sent after a flushing seek.

Send FLUSH_STOP right after forwarding the seek event upstream if necessary.
This makes sure that adder->srcpad is not left flushing if seeking fails or if
upstream is blocked.

The same fix was already applied to videomixer in 49b2a946.

1 files changed, 16 insertions, 10 deletions

diff --git a/gst/adder/gstadder.c b/gst/adder/gstadder.c
index 184421d29..3d092e74f 100644
--- a/gst/adder/gstadder.c
+++ b/gst/adder/gstadder.c
@@ -685,6 +685,14 @@ gst_adder_src_event (GstPad * pad, GstEvent * event)
         /* flushing seek, start flush downstream, the flush will be done
          * when all pads received a FLUSH_STOP. */
         gst_pad_push_event (adder->srcpad, gst_event_new_flush_start ());
+
+        /* We can't send FLUSH_STOP here since upstream could start pushing data
+         * after we unlock adder->collect.
+         * We set flush_stop_pending to TRUE instead and send FLUSH_STOP after
+         * forwarding the seek upstream or from gst_adder_collected,
+         * whichever happens first.
+         */
+        adder->flush_stop_pending = TRUE;
       }
       GST_DEBUG_OBJECT (adder, "handling seek event: %" GST_PTR_FORMAT, event);
 
@@ -708,10 +716,6 @@ gst_adder_src_event (GstPad * pad, GstEvent * event)
          * have stopped so that the cookie gets properly updated. */
         gst_collect_pads_set_flushing (adder->collect, TRUE);
       }
-      /* we might have a pending flush_stop event now. This event will either be
-       * sent by an upstream element when it completes the seek or we will push
-       * one in the collected callback ourself */
-      adder->flush_stop_pending = flush;
       GST_OBJECT_UNLOCK (adder->collect);
       GST_DEBUG_OBJECT (adder, "forwarding seek event: %" GST_PTR_FORMAT,
           event);
@@ -721,10 +725,11 @@ gst_adder_src_event (GstPad * pad, GstEvent * event)
         /* seek failed. maybe source is a live source. */
         GST_DEBUG_OBJECT (adder, "seeking failed");
       }
-      /* FIXME: ideally we would like to send a flush-stop event from here but
-       * collectpads does not have a method that allows us to do that. Instead
-       * we forward all flush-stop events we receive on the sinkpads. We might
-       * be sending too many flush-stop events. */
+      if (g_atomic_int_compare_and_exchange (&adder->flush_stop_pending,
+              TRUE, FALSE)) {
+        GST_DEBUG_OBJECT (adder, "pending flush stop");
+        gst_pad_push_event (adder->srcpad, gst_event_new_flush_stop ());
+      }
       break;
     }
     case GST_EVENT_QOS:
@@ -1055,9 +1060,10 @@ gst_adder_collected (GstCollectPads * pads, gpointer user_data)
   if (G_UNLIKELY (adder->func == NULL))
     goto not_negotiated;
 
-  if (adder->flush_stop_pending) {
+  if (g_atomic_int_compare_and_exchange (&adder->flush_stop_pending,
+          TRUE, FALSE)) {
+    GST_DEBUG_OBJECT (adder, "pending flush stop");
     gst_pad_push_event (adder->srcpad, gst_event_new_flush_stop ());
-    adder->flush_stop_pending = FALSE;
   }
 
   /* get available bytes for reading, this can be 0 which could mean empty