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

src/spaces.cc

 // 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 542 matching lines @@
       if (!code_range->UncommitRawMemory(start, length)) return false;
     }
   }
 
   area_end_ = area_start_ + requested;
   return true;
 }
 
 
 void MemoryChunk::InsertAfter(MemoryChunk* other) {
-  next_chunk_ = other->next_chunk_;
-  prev_chunk_ = other;
+  MemoryChunk* other_next = other->next_chunk();
 
-  // This memory barrier is needed since concurrent sweeper threads may iterate
-  // over the list of pages while a new page is inserted.
-  // TODO(hpayer): find a cleaner way to guarantee that the page list can be
-  // expanded concurrently
-  MemoryBarrier();
-
-  // The following two write operations can take effect in arbitrary order
-  // since pages are always iterated by the sweeper threads in LIFO order, i.e,
-  // the inserted page becomes visible for the sweeper threads after
-  // other->next_chunk_ = this;
-  other->next_chunk_->prev_chunk_ = this;
-  other->next_chunk_ = this;
+  set_next_chunk(other_next);
+  set_prev_chunk(other);
+  other_next->set_prev_chunk(this);
+  other->set_next_chunk(this);
 }
 
 
 void MemoryChunk::Unlink() {
   if (!InNewSpace() && IsFlagSet(SCAN_ON_SCAVENGE)) {
     heap_->decrement_scan_on_scavenge_pages();
     ClearFlag(SCAN_ON_SCAVENGE);
   }
-  next_chunk_->prev_chunk_ = prev_chunk_;
-  prev_chunk_->next_chunk_ = next_chunk_;
-  prev_chunk_ = NULL;
-  next_chunk_ = NULL;
+  MemoryChunk* next_element = next_chunk();
+  MemoryChunk* prev_element = prev_chunk();
+  next_element->set_prev_chunk(prev_element);
+  prev_element->set_next_chunk(next_element);
+  set_prev_chunk(NULL);
+  set_next_chunk(NULL);
 }
 
 
 MemoryChunk* MemoryAllocator::AllocateChunk(intptr_t reserve_area_size,
                                             intptr_t commit_area_size,
                                             Executability executable,
                                             Space* owner) {
   ASSERT(commit_area_size <= reserve_area_size);
 
   size_t chunk_size;
@@ skipping 2601 matching lines @@
     object->ShortPrint();
     PrintF("\n");
   }
   printf(" --------------------------------------\n");
   printf(" Marked: %x, LiveCount: %x\n", mark_size, LiveBytes());
 }
 
 #endif  // DEBUG
 
 } }  // namespace v8::internal