[heap] Initialize the owner on each page after lospace allocation

src/heap/spaces-inl.h

Index: src/heap/spaces-inl.h
diff --git a/src/heap/spaces-inl.h b/src/heap/spaces-inl.h
index 685611e8151527a150a952be9ce47d28b64c0167..3d40a5457ad0a747ac4e8253db809d149b0b3958 100644
--- a/src/heap/spaces-inl.h
+++ b/src/heap/spaces-inl.h
@@ -590,6 +590,17 @@ LargePage* LargePage::Initialize(Heap* heap, MemoryChunk* chunk,
     FATAL("Code page is too large.");
   }
   heap->incremental_marking()->SetOldSpacePageFlags(chunk);
+
+  // Initialize the owner field for each contained page (except the first, which
+  // is initialized by MemoryChunk::Initialize).
+  for (size_t i = Page::kPageSize; i < chunk->size(); i += Page::kPageSize) {
+    Address& owner_addr =
+        Memory::Address_at(chunk->address() + i + Page::kOwnerOffset);
+    const Address new_owner_value = reinterpret_cast<Address>(
+        reinterpret_cast<intptr_t>(owner_addr) & ~kPageHeaderTagMask);
+    owner_addr = new_owner_value;

[Michael Lippautz, 2016/12/09 20:09:40]

Please just write
  // Clear out  kPageHeaderTag. 
  owner_addr = 0;
here.

This value will be overwritten by the mutator with an actual payload value
anyways. The only important thing here is that we write a value without the 2nd
bit set.

[jgruber, 2016/12/12 12:48:07]

Done.

+  }
+
   return static_cast<LargePage*>(chunk);
 }