[heap] Fix more data races in bitmap SetRange and ClearRange.

This patch also changes String body descriptor to use synchronized
length and adds atomic live_bytes accessor.

BUG=chromium:694255

Change-Id: I41233b2097ec5c6a4ea2c45d4b8febf7ffca155e
Reviewed-on: https://chromium-review.googlesource.com/527093
Reviewed-by: Hannes Payer <hpayer@chromium.org>
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#45761}

src/heap/marking.h

@@ -197,10 +197,9 @@ class Bitmap {
       // cell with 1s.
       SetBitsInCell<mode>(start_cell_index, ~(start_index_mask - 1));
       // Then fill all in between cells with 1s.
+      base::Atomic32* cell_base = reinterpret_cast<base::Atomic32*>(cells());
       for (unsigned int i = start_cell_index + 1; i < end_cell_index; i++) {
-        // The callers must ensure that the inner cells in the range are not
-        // accessed concurrently.
-        cells()[i] = ~0u;
+        base::Relaxed_Store(cell_base + i, ~0u);
       }
       // Finally, fill all bits until the end address in the last cell with 1s.
       SetBitsInCell<mode>(end_cell_index, (end_index_mask - 1));
@@ -227,10 +226,9 @@ class Bitmap {
       // cell with 0s.
       ClearBitsInCell<mode>(start_cell_index, ~(start_index_mask - 1));
       // Then fill all in between cells with 0s.
+      base::Atomic32* cell_base = reinterpret_cast<base::Atomic32*>(cells());
       for (unsigned int i = start_cell_index + 1; i < end_cell_index; i++) {
-        // The callers must ensure that the inner cells in the range are not
-        // accessed concurrently.
-        cells()[i] = 0;
+        base::Relaxed_Store(cell_base + i, 0);
       }
       // Finally, set all bits until the end address in the last cell with 0s.
       ClearBitsInCell<mode>(end_cell_index, (end_index_mask - 1));

src/heap/spaces.cc

@@ -1504,9 +1504,11 @@ void PagedSpace::EmptyAllocationInfo() {
 
     // Clear the bits in the unused black area.
     if (current_top != current_limit) {
-      MarkingState::Internal(page).bitmap()->ClearRange(
-          page->AddressToMarkbitIndex(current_top),
-          page->AddressToMarkbitIndex(current_limit));
+      MarkingState::Internal(page)
+          .bitmap()
+          ->ClearRange<IncrementalMarking::kAtomicity>(
+              page->AddressToMarkbitIndex(current_top),
+              page->AddressToMarkbitIndex(current_limit));
       MarkingState::Internal(page)
           .IncrementLiveBytes<IncrementalMarking::kAtomicity>(
               -static_cast<int>(current_limit - current_top));
@@ -1595,7 +1597,8 @@ void PagedSpace::Verify(ObjectVisitor* visitor) {
       CHECK(object->address() + size <= top);
       end_of_previous_object = object->address() + size;
     }
-    CHECK_LE(black_size, MarkingState::Internal(page).live_bytes());
+    CHECK_LE(black_size,
+             MarkingState::Internal(page).live_bytes<MarkBit::ATOMIC>());
   }
   CHECK(allocation_pointer_found_in_space);
 }

src/heap/spaces.h

@@ -695,7 +695,9 @@ class MarkingState {
   }
 
   Bitmap* bitmap() const { return bitmap_; }
-  intptr_t live_bytes() const { return *live_bytes_; }
+
+  template <MarkBit::AccessMode mode = MarkBit::NON_ATOMIC>
+  inline intptr_t live_bytes() const;
 
  private:
   Bitmap* bitmap_;
@@ -714,6 +716,16 @@ inline void MarkingState::IncrementLiveBytes<MarkBit::ATOMIC>(
   reinterpret_cast<base::AtomicNumber<intptr_t>*>(live_bytes_)->Increment(by);
 }
 
+template <>
+inline intptr_t MarkingState::live_bytes<MarkBit::NON_ATOMIC>() const {
+  return *live_bytes_;
+}
+
+template <>
+inline intptr_t MarkingState::live_bytes<MarkBit::ATOMIC>() const {
+  return reinterpret_cast<base::AtomicNumber<intptr_t>*>(live_bytes_)->Value();
+}
+
 // -----------------------------------------------------------------------------
 // A page is a memory chunk of a size 1MB. Large object pages may be larger.
 //

src/objects-body-descriptors-inl.h

@@ -546,7 +546,7 @@ class SeqOneByteString::BodyDescriptor final : public BodyDescriptorBase {
 
   static inline int SizeOf(Map* map, HeapObject* obj) {
     SeqOneByteString* string = SeqOneByteString::cast(obj);
-    return string->SizeFor(string->length());
+    return string->SizeFor(string->synchronized_length());
   }
 };
 
@@ -563,7 +563,7 @@ class SeqTwoByteString::BodyDescriptor final : public BodyDescriptorBase {
 
   static inline int SizeOf(Map* map, HeapObject* obj) {
     SeqTwoByteString* string = SeqTwoByteString::cast(obj);
-    return string->SizeFor(string->length());
+    return string->SizeFor(string->synchronized_length());
   }
 };