diff --git a/.hgtags-top-repo b/.hgtags-top-repo
index 9ed3c0b1f24d51e60f58e50801c6e99e5005e58d..a5ae9ea7b47730030bd2025b7b17b6e2c932e1cb 100644
--- a/.hgtags-top-repo
+++ b/.hgtags-top-repo
@@ -441,3 +441,6 @@ ec4159ebe7050fcc5dcee8a2d150cf948ecc97db jdk-9+178
 252475ccfd84cc249f8d6faf4b7806b5e2c384ce jdk-9+179
 a133a7d1007b1456bc62824382fd8ac93b45d329 jdk-10+17
 536b81db8075486ca0fe3225d8e59313df5b936c jdk-10+18
+b803e6cff41e72a1e6d8782e1ef7c25a6e3e5ee3 jdk-10+19
+d2982a786f53814367698e63efe6349c9128e1db jdk-9+180
+b656dea9398ef601f7fc08d1a5157a560e0ccbe0 jdk-9+181
diff --git a/hotspot/.hgtags b/hotspot/.hgtags
index bd997249d7d386801c460522cb31e947b08bc242..282c094083050378ec879ba18903a875f40bcf8f 100644
--- a/hotspot/.hgtags
+++ b/hotspot/.hgtags
@@ -601,3 +601,6 @@ c1f3649a3a42f124b418a5a916dbad13d059b757 jdk-10+15
 d2661aa42bff322badbe6c1337fc638d2e0f5730 jdk-9+179
 73e2cb8700bfa51304bd4b02f224620859a3f600 jdk-10+17
 c9d3317623d48da3327232c81e3f8cfc0d29d888 jdk-10+18
+33b74e13c1457f36041addb8b850831f81ca6e9f jdk-10+19
+d7baadc223e790c08bc69bf7e553bce65b4e7e40 jdk-9+180
+4a443796f6f57842d6a0434ac27ca3d1033ccc20 jdk-9+181
diff --git a/hotspot/src/share/vm/gc/g1/g1CollectedHeap.cpp b/hotspot/src/share/vm/gc/g1/g1CollectedHeap.cpp
index fce91a80ad36c23112eff55c3a0bfe824e6a18af..c044e9a0181728a2fa8126923c94cd68f6015dc5 100644
--- a/hotspot/src/share/vm/gc/g1/g1CollectedHeap.cpp
+++ b/hotspot/src/share/vm/gc/g1/g1CollectedHeap.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2001, 2016, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2001, 2017, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -4389,6 +4389,15 @@ void G1CollectedHeap::enqueue_discovered_references(G1ParScanThreadStateSet* per
   rp->verify_no_references_recorded();
   assert(!rp->discovery_enabled(), "should have been disabled");
 
+  // If during an initial mark pause we install a pending list head which is not otherwise reachable
+  // ensure that it is marked in the bitmap for concurrent marking to discover.
+  if (collector_state()->during_initial_mark_pause()) {
+    oop pll_head = Universe::reference_pending_list();
+    if (pll_head != NULL) {
+      _cm->grayRoot(pll_head);
+    }
+  }
+
   // FIXME
   // CM's reference processing also cleans up the string and symbol tables.
   // Should we do that here also? We could, but it is a serial operation
diff --git a/hotspot/src/share/vm/memory/universe.cpp b/hotspot/src/share/vm/memory/universe.cpp
index d56e8dd3226bb781dc77f56d347da546f193ff1f..2d9dded4872d768369ce5b05d1de28fa134a6b64 100644
--- a/hotspot/src/share/vm/memory/universe.cpp
+++ b/hotspot/src/share/vm/memory/universe.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1997, 2016, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1997, 2017, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -497,7 +497,11 @@ void Universe::fixup_mirrors(TRAPS) {
 #define assert_pll_ownership() assert_pll_locked(owned_by_self)
 
 oop Universe::reference_pending_list() {
-  assert_pll_ownership();
+  if (Thread::current()->is_VM_thread()) {
+    assert_pll_locked(is_locked);
+  } else {
+    assert_pll_ownership();
+  }
   return _reference_pending_list;
 }