--- a/src/hotspot/share/gc/g1/g1ConcurrentMark.cpp	Wed Jun 26 09:06:32 2019 -0400
+++ b/src/hotspot/share/gc/g1/g1ConcurrentMark.cpp	Wed Jun 26 13:18:38 2019 -0400
@@ -2419,12 +2419,13 @@
     abort_marking_if_regular_check_fail();
   }
 
+  // Can't assert qset is empty here, even if not aborted.  If concurrent,
+  // some other thread might be adding to the queue.  If not concurrent,
+  // some other thread might have won the race for the last buffer, but
+  // has not yet decremented the count.
+
   _draining_satb_buffers = false;
 
-  assert(has_aborted() ||
-         _cm->concurrent() ||
-         satb_mq_set.completed_buffers_num() == 0, "invariant");
-
   // again, this was a potentially expensive operation, decrease the
   // limits to get the regular clock call early
   decrease_limits();