Make prev and next pointer in pages list AtomicWords and access them using acquire/release semantic…

src/spaces.h

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 295 matching lines @@
     return reinterpret_cast<MemoryChunk*>(OffsetFrom(a) & ~kAlignmentMask);
   }
 
   // Only works for addresses in pointer spaces, not data or code spaces.
   static inline MemoryChunk* FromAnyPointerAddress(Heap* heap, Address addr);
 
   Address address() { return reinterpret_cast<Address>(this); }
 
   bool is_valid() { return address() != NULL; }
 
-  MemoryChunk* next_chunk() const { return next_chunk_; }
-  MemoryChunk* prev_chunk() const { return prev_chunk_; }
+  MemoryChunk* next_chunk() const {
+    return reinterpret_cast<MemoryChunk*>(Acquire_Load(&next_chunk_));
+  }
 
-  void set_next_chunk(MemoryChunk* next) { next_chunk_ = next; }
-  void set_prev_chunk(MemoryChunk* prev) { prev_chunk_ = prev; }
+  MemoryChunk* prev_chunk() const {
+    return reinterpret_cast<MemoryChunk*>(Acquire_Load(&prev_chunk_));
+  }
+
+  void set_next_chunk(MemoryChunk* next) {
+    Release_Store(&next_chunk_, reinterpret_cast<AtomicWord>(next));
+  }
+
+  void set_prev_chunk(MemoryChunk* prev) {
+    Release_Store(&prev_chunk_, reinterpret_cast<AtomicWord>(prev));
+  }
 
   Space* owner() const {
     if ((reinterpret_cast<intptr_t>(owner_) & kFailureTagMask) ==
         kFailureTag) {
       return reinterpret_cast<Space*>(reinterpret_cast<intptr_t>(owner_) -
                                       kFailureTag);
     } else {
       return NULL;
     }
   }
@@ skipping 198 matching lines @@
     MemoryChunk::FromAddress(address)->IncrementLiveBytes(by);
   }
 
   static void IncrementLiveBytesFromMutator(Address address, int by);
 
   static const intptr_t kAlignment =
       (static_cast<uintptr_t>(1) << kPageSizeBits);
 
   static const intptr_t kAlignmentMask = kAlignment - 1;
 
-  static const intptr_t kSizeOffset = kPointerSize + kPointerSize;
+  static const intptr_t kSizeOffset = 0;
 
   static const intptr_t kLiveBytesOffset =
      kSizeOffset + kPointerSize + kPointerSize + kPointerSize +
      kPointerSize + kPointerSize +
      kPointerSize + kPointerSize + kPointerSize + kIntSize;
 
   static const size_t kSlotsBufferOffset = kLiveBytesOffset + kIntSize;
 
   static const size_t kWriteBarrierCounterOffset =
       kSlotsBufferOffset + kPointerSize + kPointerSize;
 
   static const size_t kHeaderSize = kWriteBarrierCounterOffset + kPointerSize +
                                     kIntSize + kIntSize + kPointerSize +
-                                    5 * kPointerSize;
+                                    5 * kPointerSize +
+                                    kPointerSize + kPointerSize;
 
   static const int kBodyOffset =
       CODE_POINTER_ALIGN(kHeaderSize + Bitmap::kSize);
 
   // The start offset of the object area in a page. Aligned to both maps and
   // code alignment to be suitable for both.  Also aligned to 32 words because
   // the marking bitmap is arranged in 32 bit chunks.
   static const int kObjectStartAlignment = 32 * kPointerSize;
   static const int kObjectStartOffset = kBodyOffset - 1 +
       (kObjectStartAlignment - (kBodyOffset - 1) % kObjectStartAlignment);
@@ skipping 51 matching lines @@
 
   inline Address MarkbitIndexToAddress(uint32_t index) {
     return this->address() + (index << kPointerSizeLog2);
   }
 
   void InsertAfter(MemoryChunk* other);
   void Unlink();
 
   inline Heap* heap() { return heap_; }
 
-  static const int kFlagsOffset = kPointerSize * 3;
+  static const int kFlagsOffset = kPointerSize;
 
   bool IsEvacuationCandidate() { return IsFlagSet(EVACUATION_CANDIDATE); }
 
   bool ShouldSkipEvacuationSlotRecording() {
     return (flags_ & kSkipEvacuationSlotsRecordingMask) != 0;
   }
 
   inline SkipList* skip_list() {
     return skip_list_;
   }
@@ skipping 28 matching lines @@
   bool CommitArea(size_t requested);
 
   // Approximate amount of physical memory committed for this chunk.
   size_t CommittedPhysicalMemory() {
     return high_water_mark_;
   }
 
   static inline void UpdateHighWaterMark(Address mark);
 
  protected:
-  MemoryChunk* next_chunk_;
-  MemoryChunk* prev_chunk_;
   size_t size_;
   intptr_t flags_;
 
   // Start and end of allocatable memory on this chunk.
   Address area_start_;
   Address area_end_;
 
   // If the chunk needs to remember its memory reservation, it is stored here.
   VirtualMemory reservation_;
   // The identity of the owning space.  This is tagged as a failure pointer, but
@@ skipping 26 matching lines @@
   intptr_t non_available_small_blocks_;
 
   static MemoryChunk* Initialize(Heap* heap,
                                  Address base,
                                  size_t size,
                                  Address area_start,
                                  Address area_end,
                                  Executability executable,
                                  Space* owner);
 
+ private:
+  // next_chunk_ holds a pointer of type MemoryChunk
+  AtomicWord next_chunk_;
+  // prev_chunk_ holds a pointer of type MemoryChunk
+  AtomicWord prev_chunk_;
+
   friend class MemoryAllocator;
 };
 
 
 STATIC_CHECK(sizeof(MemoryChunk) <= MemoryChunk::kHeaderSize);
 
 
 // -----------------------------------------------------------------------------
 // A page is a memory chunk of a size 1MB. Large object pages may be larger.
 //
@@ skipping 2210 matching lines @@
   }
   // Must be small, since an iteration is used for lookup.
   static const int kMaxComments = 64;
 };
 #endif
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_SPACES_H_