--- a/src/share/vm/gc_implementation/g1/g1BlockOffsetTable.cpp	Mon Oct 18 15:01:41 2010 -0700
+++ b/src/share/vm/gc_implementation/g1/g1BlockOffsetTable.cpp	Sat Oct 16 17:12:19 2010 -0400
@@ -175,7 +175,7 @@
   }
   assert(start_card > _array->index_for(_bottom), "Cannot be first card");
   assert(_array->offset_array(start_card-1) <= N_words,
-    "Offset card has an unexpected value");
+         "Offset card has an unexpected value");
   size_t start_card_for_region = start_card;
   u_char offset = max_jubyte;
   for (int i = 0; i < BlockOffsetArray::N_powers; i++) {
@@ -577,6 +577,16 @@
 #endif
 }
 
+void
+G1BlockOffsetArray::set_for_starts_humongous(HeapWord* new_end) {
+  assert(_end ==  new_end, "_end should have already been updated");
+
+  // The first BOT entry should have offset 0.
+  _array->set_offset_array(_array->index_for(_bottom), 0);
+  // The rest should point to the first one.
+  set_remainder_to_point_to_start(_bottom + N_words, new_end);
+}
+
 //////////////////////////////////////////////////////////////////////
 // G1BlockOffsetArrayContigSpace
 //////////////////////////////////////////////////////////////////////
@@ -626,3 +636,12 @@
          "Precondition of call");
   _array->set_offset_array(bottom_index, 0);
 }
+
+void
+G1BlockOffsetArrayContigSpace::set_for_starts_humongous(HeapWord* new_end) {
+  G1BlockOffsetArray::set_for_starts_humongous(new_end);
+
+  // Make sure _next_offset_threshold and _next_offset_index point to new_end.
+  _next_offset_threshold = new_end;
+  _next_offset_index     = _array->index_for(new_end);
+}

--- a/src/share/vm/gc_implementation/g1/g1BlockOffsetTable.hpp	Mon Oct 18 15:01:41 2010 -0700
+++ b/src/share/vm/gc_implementation/g1/g1BlockOffsetTable.hpp	Sat Oct 16 17:12:19 2010 -0400
@@ -436,6 +436,8 @@
   }
 
   void check_all_cards(size_t left_card, size_t right_card) const;
+
+  virtual void set_for_starts_humongous(HeapWord* new_end);
 };
 
 // A subtype of BlockOffsetArray that takes advantage of the fact
@@ -484,4 +486,6 @@
 
   HeapWord* block_start_unsafe(const void* addr);
   HeapWord* block_start_unsafe_const(const void* addr) const;
+
+  virtual void set_for_starts_humongous(HeapWord* new_end);
 };

--- a/src/share/vm/gc_implementation/g1/heapRegion.cpp	Mon Oct 18 15:01:41 2010 -0700
+++ b/src/share/vm/gc_implementation/g1/heapRegion.cpp	Sat Oct 16 17:12:19 2010 -0400
@@ -377,10 +377,26 @@
 }
 // </PREDICTION>
 
-void HeapRegion::set_startsHumongous() {
+void HeapRegion::set_startsHumongous(HeapWord* new_end) {
+  assert(end() == _orig_end,
+         "Should be normal before the humongous object allocation");
+  assert(top() == bottom(), "should be empty");
+
   _humongous_type = StartsHumongous;
   _humongous_start_region = this;
-  assert(end() == _orig_end, "Should be normal before alloc.");
+
+  set_end(new_end);
+  _offsets.set_for_starts_humongous(new_end);
+}
+
+void HeapRegion::set_continuesHumongous(HeapRegion* start) {
+  assert(end() == _orig_end,
+         "Should be normal before the humongous object allocation");
+  assert(top() == bottom(), "should be empty");
+  assert(start->startsHumongous(), "pre-condition");
+
+  _humongous_type = ContinuesHumongous;
+  _humongous_start_region = start;
 }
 
 bool HeapRegion::claimHeapRegion(jint claimValue) {
@@ -500,23 +516,6 @@
   return blk.result();
 }
 
-void HeapRegion::set_continuesHumongous(HeapRegion* start) {
-  // The order is important here.
-  start->add_continuingHumongousRegion(this);
-  _humongous_type = ContinuesHumongous;
-  _humongous_start_region = start;
-}
-
-void HeapRegion::add_continuingHumongousRegion(HeapRegion* cont) {
-  // Must join the blocks of the current H region seq with the block of the
-  // added region.
-  offsets()->join_blocks(bottom(), cont->bottom());
-  arrayOop obj = (arrayOop)(bottom());
-  obj->set_length((int) (obj->length() + cont->capacity()/jintSize));
-  set_end(cont->end());
-  set_top(cont->end());
-}
-
 void HeapRegion::save_marks() {
   set_saved_mark();
 }

--- a/src/share/vm/gc_implementation/g1/heapRegion.hpp	Mon Oct 18 15:01:41 2010 -0700
+++ b/src/share/vm/gc_implementation/g1/heapRegion.hpp	Sat Oct 16 17:12:19 2010 -0400
@@ -395,14 +395,12 @@
 
   // Causes the current region to represent a humongous object spanning "n"
   // regions.
-  virtual void set_startsHumongous();
+  void set_startsHumongous(HeapWord* new_end);
 
   // The regions that continue a humongous sequence should be added using
   // this method, in increasing address order.
   void set_continuesHumongous(HeapRegion* start);
 
-  void add_continuingHumongousRegion(HeapRegion* cont);
-
   // If the region has a remembered set, return a pointer to it.
   HeapRegionRemSet* rem_set() const {
     return _rem_set;
@@ -733,13 +731,6 @@
                                    FilterOutOfRegionClosure* cl,
                                    bool filter_young);
 
-  // The region "mr" is entirely in "this", and starts and ends at block
-  // boundaries. The caller declares that all the contained blocks are
-  // coalesced into one.
-  void declare_filled_region_to_BOT(MemRegion mr) {
-    _offsets.single_block(mr.start(), mr.end());
-  }
-
   // A version of block start that is guaranteed to find *some* block
   // boundary at or before "p", but does not object iteration, and may
   // therefore be used safely when the heap is unparseable.

--- a/src/share/vm/gc_implementation/g1/heapRegionSeq.cpp	Mon Oct 18 15:01:41 2010 -0700
+++ b/src/share/vm/gc_implementation/g1/heapRegionSeq.cpp	Sat Oct 16 17:12:19 2010 -0400
@@ -91,34 +91,118 @@
   }
   if (sumSizes >= word_size) {
     _alloc_search_start = cur;
-    // Mark the allocated regions as allocated.
+
+    // We need to initialize the region(s) we just discovered. This is
+    // a bit tricky given that it can happen concurrently with
+    // refinement threads refining cards on these regions and
+    // potentially wanting to refine the BOT as they are scanning
+    // those cards (this can happen shortly after a cleanup; see CR
+    // 6991377). So we have to set up the region(s) carefully and in
+    // a specific order.
+
+    // Currently, allocs_are_zero_filled() returns false. The zero
+    // filling infrastructure will be going away soon (see CR 6977804).
+    // So no need to do anything else here.
     bool zf = G1CollectedHeap::heap()->allocs_are_zero_filled();
+    assert(!zf, "not supported");
+
+    // This will be the "starts humongous" region.
     HeapRegion* first_hr = _regions.at(first);
-    for (int i = first; i < cur; i++) {
-      HeapRegion* hr = _regions.at(i);
-      if (zf)
-        hr->ensure_zero_filled();
+    {
+      MutexLockerEx x(ZF_mon, Mutex::_no_safepoint_check_flag);
+      first_hr->set_zero_fill_allocated();
+    }
+    // The header of the new object will be placed at the bottom of
+    // the first region.
+    HeapWord* new_obj = first_hr->bottom();
+    // This will be the new end of the first region in the series that
+    // should also match the end of the last region in the seriers.
+    // (Note: sumSizes = "region size" x "number of regions we found").
+    HeapWord* new_end = new_obj + sumSizes;
+    // This will be the new top of the first region that will reflect
+    // this allocation.
+    HeapWord* new_top = new_obj + word_size;
+
+    // First, we need to zero the header of the space that we will be
+    // allocating. When we update top further down, some refinement
+    // threads might try to scan the region. By zeroing the header we
+    // ensure that any thread that will try to scan the region will
+    // come across the zero klass word and bail out.
+    //
+    // NOTE: It would not have been correct to have used
+    // CollectedHeap::fill_with_object() and make the space look like
+    // an int array. The thread that is doing the allocation will
+    // later update the object header to a potentially different array
+    // type and, for a very short period of time, the klass and length
+    // fields will be inconsistent. This could cause a refinement
+    // thread to calculate the object size incorrectly.
+    Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
+
+    // We will set up the first region as "starts humongous". This
+    // will also update the BOT covering all the regions to reflect
+    // that there is a single object that starts at the bottom of the
+    // first region.
+    first_hr->set_startsHumongous(new_end);
+
+    // Then, if there are any, we will set up the "continues
+    // humongous" regions.
+    HeapRegion* hr = NULL;
+    for (int i = first + 1; i < cur; ++i) {
+      hr = _regions.at(i);
       {
         MutexLockerEx x(ZF_mon, Mutex::_no_safepoint_check_flag);
         hr->set_zero_fill_allocated();
       }
-      size_t sz = hr->capacity() / HeapWordSize;
-      HeapWord* tmp = hr->allocate(sz);
-      assert(tmp != NULL, "Humongous allocation failure");
-      MemRegion mr = MemRegion(tmp, sz);
-      CollectedHeap::fill_with_object(mr);
-      hr->declare_filled_region_to_BOT(mr);
-      if (i == first) {
-        first_hr->set_startsHumongous();
+      hr->set_continuesHumongous(first_hr);
+    }
+    // If we have "continues humongous" regions (hr != NULL), then the
+    // end of the last one should match new_end.
+    assert(hr == NULL || hr->end() == new_end, "sanity");
+
+    // Up to this point no concurrent thread would have been able to
+    // do any scanning on any region in this series. All the top
+    // fields still point to bottom, so the intersection between
+    // [bottom,top] and [card_start,card_end] will be empty. Before we
+    // update the top fields, we'll do a storestore to make sure that
+    // no thread sees the update to top before the zeroing of the
+    // object header and the BOT initialization.
+    OrderAccess::storestore();
+
+    // Now that the BOT and the object header have been initialized,
+    // we can update top of the "starts humongous" region.
+    assert(first_hr->bottom() < new_top && new_top <= first_hr->end(),
+           "new_top should be in this region");
+    first_hr->set_top(new_top);
+
+    // Now, we will update the top fields of the "continues humongous"
+    // regions. The reason we need to do this is that, otherwise,
+    // these regions would look empty and this will confuse parts of
+    // G1. For example, the code that looks for a consecutive number
+    // of empty regions will consider them empty and try to
+    // re-allocate them. We can extend is_empty() to also include
+    // !continuesHumongous(), but it is easier to just update the top
+    // fields here.
+    hr = NULL;
+    for (int i = first + 1; i < cur; ++i) {
+      hr = _regions.at(i);
+      if ((i + 1) == cur) {
+        // last continues humongous region
+        assert(hr->bottom() < new_top && new_top <= hr->end(),
+               "new_top should fall on this region");
+        hr->set_top(new_top);
       } else {
-        assert(i > first, "sanity");
-        hr->set_continuesHumongous(first_hr);
+        // not last one
+        assert(new_top > hr->end(), "new_top should be above this region");
+        hr->set_top(hr->end());
       }
     }
-    HeapWord* first_hr_bot = first_hr->bottom();
-    HeapWord* obj_end = first_hr_bot + word_size;
-    first_hr->set_top(obj_end);
-    return first_hr_bot;
+    // If we have continues humongous regions (hr != NULL), then the
+    // end of the last one should match new_end and its top should
+    // match new_top.
+    assert(hr == NULL ||
+           (hr->end() == new_end && hr->top() == new_top), "sanity");
+
+    return new_obj;
   } else {
     // If we started from the beginning, we want to know why we can't alloc.
     return NULL;

--- a/src/share/vm/gc_implementation/g1/sparsePRT.cpp	Mon Oct 18 15:01:41 2010 -0700
+++ b/src/share/vm/gc_implementation/g1/sparsePRT.cpp	Sat Oct 16 17:12:19 2010 -0400
@@ -308,7 +308,7 @@
   assert(e2->num_valid_cards() > 0, "Postcondition.");
 }
 
-CardIdx_t /* RSHashTable:: */ RSHashTableIter::find_first_card_in_list() {
+CardIdx_t RSHashTableIter::find_first_card_in_list() {
   CardIdx_t res;
   while (_bl_ind != RSHashTable::NullEntry) {
     res = _rsht->entry(_bl_ind)->card(0);
@@ -322,11 +322,11 @@
   return SparsePRTEntry::NullEntry;
 }
 
-size_t /* RSHashTable:: */ RSHashTableIter::compute_card_ind(CardIdx_t ci) {
+size_t RSHashTableIter::compute_card_ind(CardIdx_t ci) {
   return (_rsht->entry(_bl_ind)->r_ind() * HeapRegion::CardsPerRegion) + ci;
 }
 
-bool /* RSHashTable:: */ RSHashTableIter::has_next(size_t& card_index) {
+bool RSHashTableIter::has_next(size_t& card_index) {
   _card_ind++;
   CardIdx_t ci;
   if (_card_ind < SparsePRTEntry::cards_num() &&

--- a/src/share/vm/gc_implementation/g1/sparsePRT.hpp	Mon Oct 18 15:01:41 2010 -0700
+++ b/src/share/vm/gc_implementation/g1/sparsePRT.hpp	Sat Oct 16 17:12:19 2010 -0400
@@ -282,8 +282,6 @@
 
 class SparsePRTIter: public RSHashTableIter {
 public:
-  SparsePRTIter() : RSHashTableIter() { }
-
   void init(const SparsePRT* sprt) {
     RSHashTableIter::init(sprt->cur());
   }