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

src/heap/spaces-inl.h

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_HEAP_SPACES_INL_H_
 #define V8_HEAP_SPACES_INL_H_
 
 #include "src/heap/incremental-marking.h"
 #include "src/heap/spaces.h"
 #include "src/isolate.h"
@@ skipping 572 matching lines @@
   return AllocateRaw(size_in_bytes, alignment);
 }
 
 LargePage* LargePage::Initialize(Heap* heap, MemoryChunk* chunk,
                                  Executability executable, Space* owner) {
   if (executable && chunk->size() > LargePage::kMaxCodePageSize) {
     STATIC_ASSERT(LargePage::kMaxCodePageSize <= TypedSlotSet::kMaxOffset);
     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);
 }
 
 size_t LargeObjectSpace::Available() {
   return ObjectSizeFor(heap()->memory_allocator()->Available());
 }
 
 
 LocalAllocationBuffer LocalAllocationBuffer::InvalidBuffer() {
   return LocalAllocationBuffer(nullptr, AllocationInfo(nullptr, nullptr));
@@ skipping 19 matching lines @@
     other->allocation_info_.Reset(nullptr, nullptr);
     return true;
   }
   return false;
 }
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_HEAP_SPACES_INL_H_