--- old/src/share/vm/gc/g1/g1CollectionSet.cpp	2016-06-28 14:13:04.957422199 +0200
+++ new/src/share/vm/gc/g1/g1CollectionSet.cpp	2016-06-28 14:13:04.861419307 +0200
@@ -26,7 +26,6 @@
 #include "gc/g1/g1CollectedHeap.hpp"
 #include "gc/g1/g1CollectionSet.hpp"
 #include "gc/g1/g1CollectorState.hpp"
-#include "gc/g1/g1FixedSizeStack.inline.hpp"
 #include "gc/g1/g1Policy.hpp"
 #include "gc/g1/heapRegion.inline.hpp"
 #include "gc/g1/heapRegionRemSet.hpp"
@@ -57,9 +56,11 @@
   _eden_region_length(0),
   _survivor_region_length(0),
   _old_region_length(0),
-  _collection_set_regions(),
   _bytes_used_before(0),
   _recorded_rs_lengths(0),
+  _collection_set_regions(NULL),
+  _collection_set_cur_length(0),
+  _collection_set_max_length(0),
   // Incremental CSet attributes
   _inc_build_state(Inactive),
   _inc_bytes_used_before(0),
@@ -70,23 +71,29 @@
 }
 
 G1CollectionSet::~G1CollectionSet() {
+  if (_collection_set_regions != NULL) {
+    FREE_C_HEAP_ARRAY(uint, _collection_set_regions);
+  }
   delete _cset_chooser;
 }
 
 void G1CollectionSet::init_region_lengths(uint eden_cset_region_length,
                                           uint survivor_cset_region_length) {
+  assert_at_safepoint(true);
+
   _eden_region_length     = eden_cset_region_length;
   _survivor_region_length = survivor_cset_region_length;
 
-  assert((size_t) young_region_length() == _collection_set_regions.length(),
-         "Young region length %u should match collection set length " SIZE_FORMAT, young_region_length(), _collection_set_regions.length());
+  assert((size_t) young_region_length() == _collection_set_cur_length,
+         "Young region length %u should match collection set length " SIZE_FORMAT, young_region_length(), _collection_set_cur_length);
 
   _old_region_length      = 0;
 }
 
 void G1CollectionSet::set_max_length(uint max_region_length) {
-  guarantee(_collection_set_regions.max_length() == 0, "Must only initialize once.");
-  _collection_set_regions.initialize(max_region_length);
+  guarantee(_collection_set_regions == NULL, "Must only initialize once.");
+  _collection_set_max_length = max_region_length;
+  _collection_set_regions = NEW_C_HEAP_ARRAY(uint, max_region_length, mtGC);
 }
 
 void G1CollectionSet::set_recorded_rs_lengths(size_t rs_lengths) {
@@ -95,13 +102,16 @@
 
 // Add the heap region at the head of the non-incremental collection set
 void G1CollectionSet::add_old_region(HeapRegion* hr) {
+  assert_at_safepoint(true);
+
   assert(_inc_build_state == Active, "Precondition");
   assert(hr->is_old(), "the region should be old");
 
   assert(!hr->in_collection_set(), "should not already be in the CSet");
   _g1->register_old_region_with_cset(hr);
 
-  _collection_set_regions.par_push(hr->hrm_index());
+  _collection_set_regions[_collection_set_cur_length++] = hr->hrm_index();
+  assert(_collection_set_cur_length <= _collection_set_max_length, "Collection set now larger than maximum size.");
   
   _bytes_used_before += hr->used();
   size_t rs_length = hr->rem_set()->occupied();
@@ -111,11 +121,9 @@
 
 // Initialize the per-collection-set information
 void G1CollectionSet::start_incremental_building() {
-  assert(_collection_set_regions.length() == 0, "Must be empty before starting a new collection set.");
+  assert(_collection_set_cur_length == 0, "Collection set must be empty before starting a new collection set.");
   assert(_inc_build_state == Inactive, "Precondition");
 
-  _collection_set_regions.clear();
-
   _inc_bytes_used_before = 0;
 
   _inc_recorded_rs_lengths = 0;
@@ -157,12 +165,18 @@
   _inc_predicted_elapsed_time_ms_diffs = 0.0;
 }
 
-void G1CollectionSet::iterate(HeapRegionClosure* cl) {
-  iterate_from(cl, 0, 1, true);
+void G1CollectionSet::clear() {
+  assert_at_safepoint(true);
+  _collection_set_cur_length = 0;
+}
+
+void G1CollectionSet::iterate(HeapRegionClosure* cl, bool may_be_aborted) {
+  iterate_from(cl, 0, 1, may_be_aborted);
 }
 
 void G1CollectionSet::iterate_from(HeapRegionClosure* cl, uint worker_id, uint total_workers, bool may_be_aborted) {
-  size_t len = _collection_set_regions.length();
+  size_t len = _collection_set_cur_length;
+  OrderAccess::loadload();
   if (len == 0) {
     return;
   }
@@ -170,10 +184,11 @@
   size_t cur_pos = start_pos;
 
   do {
-    HeapRegion* r = G1CollectedHeap::heap()->region_at(_collection_set_regions.get_by_index(cur_pos));
+    HeapRegion* r = G1CollectedHeap::heap()->region_at(_collection_set_regions[cur_pos]);
     bool result = cl->doHeapRegion(r);
     guarantee(may_be_aborted || !result, "This iteration should not abort.");
     if (result) {
+      cl->incomplete();
       return;
     }
     cur_pos++;
@@ -215,10 +230,16 @@
   assert(hr->is_young(), "invariant");
   assert(_inc_build_state == Active, "Precondition");
 
-  size_t collection_set_length = _collection_set_regions.length();
+  size_t collection_set_length = _collection_set_cur_length;
   assert(collection_set_length <= INT_MAX, "Collection set is too large with %d entries", (int)collection_set_length);
   hr->set_young_index_in_cset((int)collection_set_length);
-  _collection_set_regions.par_push(hr->hrm_index());
+
+  _collection_set_regions[_collection_set_cur_length] = hr->hrm_index();
+  // Concurrent readers must observe the store of the value in the array before an
+  // update to the length field.
+  OrderAccess::storestore();
+  _collection_set_cur_length++;
+  assert(_collection_set_cur_length <= _collection_set_max_length, "Collection set larger than maximum allowed.");
 
   // This routine is used when:
   // * adding survivor regions to the incremental cset at the end of an
@@ -266,11 +287,13 @@
 
 #ifndef PRODUCT
 bool G1CollectionSet::verify_young_ages() {
+  assert_at_safepoint(true);
+
   bool ret = true;
 
-  size_t length = _collection_set_regions.length();
+  size_t length = _collection_set_cur_length;
   for (size_t i = 0; i < length; i++) {
-    HeapRegion* curr = G1CollectedHeap::heap()->region_at(_collection_set_regions.get_by_index(i));
+    HeapRegion* curr = G1CollectedHeap::heap()->region_at(_collection_set_regions[i]);
 
     guarantee(curr->is_young(), "Region must be young but is %s", curr->get_type_str());
 
@@ -466,15 +489,17 @@
 
 #ifdef ASSERT
 void G1CollectionSet::verify_young_cset_indices() const {
+  assert_at_safepoint(true);
+
   ResourceMark rm;
   uint* heap_region_indices = NEW_RESOURCE_ARRAY(uint, young_region_length());
   for (uint i = 0; i < young_region_length(); ++i) {
     heap_region_indices[i] = (uint)-1;
   }
 
-  size_t length = _collection_set_regions.length();
+  size_t length = _collection_set_cur_length;
   for (size_t i = 0; i < length; i++) {
-    HeapRegion* hr = G1CollectedHeap::heap()->region_at(_collection_set_regions.get_by_index(i));
+    HeapRegion* hr = G1CollectedHeap::heap()->region_at(_collection_set_regions[i]);
 
     const int idx = hr->young_index_in_cset();
     assert(idx > -1, "Young index must be set for all regions in the incremental collection set but is not for region %u.", hr->hrm_index());