--- old/src/hotspot/share/gc/g1/g1CollectorState.hpp	2018-03-28 16:02:59.404893738 +0200
+++ new/src/hotspot/share/gc/g1/g1CollectorState.hpp	2018-03-28 16:02:59.128885226 +0200
@@ -64,6 +64,10 @@
   // of the initial mark pause to the end of the Cleanup pause.
   bool _mark_or_rebuild_in_progress;
 
+  // The next bitmap is currently being cleared or about to be cleared. TAMS and bitmap
+  // may be out of sync.
+  bool _clearing_next_bitmap;
+
   // Set during a full gc pause.
   bool _in_full_gc;
 
@@ -76,6 +80,7 @@
     _initiate_conc_mark_if_possible(false),
 
     _mark_or_rebuild_in_progress(false),
+    _clearing_next_bitmap(false),
     _in_full_gc(false) { }
 
   // Phase setters
@@ -89,6 +94,7 @@
   void set_initiate_conc_mark_if_possible(bool v) { _initiate_conc_mark_if_possible = v; }
 
   void set_mark_or_rebuild_in_progress(bool v) { _mark_or_rebuild_in_progress = v; }
+  void set_clearing_next_bitmap(bool v) { _clearing_next_bitmap = v; }
 
   // Phase getters
   bool in_young_only_phase() const { return _in_young_only_phase && !_in_full_gc; }
@@ -102,6 +108,7 @@
   bool initiate_conc_mark_if_possible() const { return _initiate_conc_mark_if_possible; }
 
   bool mark_or_rebuild_in_progress() const { return _mark_or_rebuild_in_progress; }
+  bool clearing_next_bitmap() const { return _clearing_next_bitmap; }
 
   G1YCType yc_type() const {
     if (in_initial_mark_gc()) {