Do not dereference handles during relocation.

src/heap.cc

 // Copyright 2012 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 1282 matching lines @@
     }
     return NULL;
   }
 
  private:
   Heap* heap_;
 };
 
 
 void Heap::Scavenge() {
+  RelocationLock relocation_lock(this);
+
 #ifdef VERIFY_HEAP
   if (FLAG_verify_heap) VerifyNonPointerSpacePointers();
 #endif
 
   gc_state_ = SCAVENGE;
 
   // Implements Cheney's copying algorithm
   LOG(isolate_, ResourceEvent("scavenge", "begin"));
 
   // Clear descriptor cache.
@@ skipping 5315 matching lines @@
     } else {
       set_hash_seed(Smi::FromInt(FLAG_hash_seed));
     }
   }
 
   LOG(isolate_, IntPtrTEvent("heap-capacity", Capacity()));
   LOG(isolate_, IntPtrTEvent("heap-available", Available()));
 
   store_buffer()->SetUp();
 
+  if (FLAG_parallel_recompilation) relocation_mutex_ = OS::CreateMutex();
+#ifdef DEBUG
+  relocation_mutex_locked_by_optimizer_thread_ = false;
+#endif  // DEBUG
+
   return true;
 }
 
 bool Heap::CreateHeapObjects() {
   // Create initial maps.
   if (!CreateInitialMaps()) return false;
   if (!CreateApiObjects()) return false;
 
   // Create initial objects
   if (!CreateInitialObjects()) return false;
@@ skipping 82 matching lines @@
   if (lo_space_ != NULL) {
     lo_space_->TearDown();
     delete lo_space_;
     lo_space_ = NULL;
   }
 
   store_buffer()->TearDown();
   incremental_marking()->TearDown();
 
   isolate_->memory_allocator()->TearDown();
+
+  delete relocation_mutex_;
 }
 
 
 void Heap::AddGCPrologueCallback(GCPrologueCallback callback, GCType gc_type) {
   ASSERT(callback != NULL);
   GCPrologueCallbackPair pair(callback, gc_type);
   ASSERT(!gc_prologue_callbacks_.Contains(pair));
   return gc_prologue_callbacks_.Add(pair);
 }
 
@@ skipping 1109 matching lines @@
   counters->size_of_FIXED_ARRAY_##name()->Decrement(      \
       static_cast<int>(object_sizes_last_time_[index]));
   FIXED_ARRAY_SUB_INSTANCE_TYPE_LIST(ADJUST_LAST_TIME_OBJECT_COUNT)
 #undef ADJUST_LAST_TIME_OBJECT_COUNT
 
   OS::MemCopy(object_counts_last_time_, object_counts_, sizeof(object_counts_));
   OS::MemCopy(object_sizes_last_time_, object_sizes_, sizeof(object_sizes_));
   ClearObjectStats();
 }
 
+
+Heap::RelocationLock::RelocationLock(Heap* heap) : heap_(heap) {
+  if (FLAG_parallel_recompilation) {
+    heap_->relocation_mutex_->Lock();
+#ifdef DEBUG
+    heap_->relocation_mutex_locked_by_optimizer_thread_ =
+        heap_->isolate()->optimizing_compiler_thread()->IsOptimizerThread();
+#endif  // DEBUG
+  }
+}
+
 } }  // namespace v8::internal