[heap] Take page lock when scavenging old to new references in Scavenger.

src/heap/heap.cc

 // Copyright 2012 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.
 
 #include "src/heap/heap.h"
 
 #include "src/accessors.h"
 #include "src/api.h"
 #include "src/assembler-inl.h"
 #include "src/ast/context-slot-cache.h"
@@ skipping 1705 matching lines @@
 
   {
     // Copy roots.
     TRACE_GC(tracer(), GCTracer::Scope::SCAVENGER_ROOTS);
     IterateRoots(&scavenge_visitor, VISIT_ALL_IN_SCAVENGE);
   }
 
   {
     // Copy objects reachable from the old generation.
     TRACE_GC(tracer(), GCTracer::Scope::SCAVENGER_OLD_TO_NEW_POINTERS);
-    RememberedSet<OLD_TO_NEW>::Iterate(this, [this](Address addr) {
-      return Scavenger::CheckAndScavengeObject(this, addr);
-    });
+    RememberedSet<OLD_TO_NEW>::Iterate(
+        this, SYNCHRONIZED, [this](Address addr) {
+          return Scavenger::CheckAndScavengeObject(this, addr);
+        });
 
     RememberedSet<OLD_TO_NEW>::IterateTyped(
-        this, [this](SlotType type, Address host_addr, Address addr) {
+        this, SYNCHRONIZED,
+        [this](SlotType type, Address host_addr, Address addr) {
           return UpdateTypedSlotHelper::UpdateTypedSlot(
               isolate(), type, addr, [this](Object** addr) {
                 // We expect that objects referenced by code are long living.
                 // If we do not force promotion, then we need to clear
                 // old_to_new slots in dead code objects after mark-compact.
                 return Scavenger::CheckAndScavengeObject(
                     this, reinterpret_cast<Address>(addr));
               });
         });
   }
@@ skipping 4659 matching lines @@
 }
 
 
 // static
 int Heap::GetStaticVisitorIdForMap(Map* map) {
   return StaticVisitorBase::GetVisitorId(map);
 }
 
 }  // namespace internal
 }  // namespace v8