--- a/hotspot/src/share/vm/gc_implementation/g1/heapRegionSet.hpp	Wed Nov 02 08:04:23 2011 +0100
+++ b/hotspot/src/share/vm/gc_implementation/g1/heapRegionSet.hpp	Mon Nov 07 22:11:12 2011 -0500
@@ -47,8 +47,18 @@
 
 class hrs_ext_msg;
 
+typedef enum {
+  HRSPhaseNone,
+  HRSPhaseEvacuation,
+  HRSPhaseCleanup,
+  HRSPhaseFullGC
+} HRSPhase;
+
+class HRSPhaseSetter;
+
 class HeapRegionSetBase VALUE_OBJ_CLASS_SPEC {
   friend class hrs_ext_msg;
+  friend class HRSPhaseSetter;
 
 protected:
   static size_t calculate_region_num(HeapRegion* hr);
@@ -80,6 +90,15 @@
   size_t      _calc_total_capacity_bytes;
   size_t      _calc_total_used_bytes;
 
+  // This is here so that it can be used in the subclasses to assert
+  // something different depending on which phase the GC is in. This
+  // can be particularly helpful in the check_mt_safety() methods.
+  static HRSPhase _phase;
+
+  // Only used by HRSPhaseSetter.
+  static void clear_phase();
+  static void set_phase(HRSPhase phase);
+
   // verify_region() is used to ensure that the contents of a region
   // added to / removed from a set are consistent. Different sets
   // make different assumptions about the regions added to them. So
@@ -177,6 +196,16 @@
   }
 };
 
+class HRSPhaseSetter {
+public:
+  HRSPhaseSetter(HRSPhase phase) {
+    HeapRegionSetBase::set_phase(phase);
+  }
+  ~HRSPhaseSetter() {
+    HeapRegionSetBase::clear_phase();
+  }
+};
+
 // These two macros are provided for convenience, to keep the uses of
 // these two asserts a bit more concise.