Serializer enable/disable flags need thread safety.

src/serialize.h

 // 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 438 matching lines @@
   }
 
   DisallowHeapAllocation no_allocation_;
   HashMap* serialization_map_;
   DISALLOW_COPY_AND_ASSIGN(SerializationAddressMapper);
 };
 
 
 class CodeAddressMap;
 
+enum SerializationState {
+  SERIALIZER_STATE_DISABLED = 0,
+  SERIALIZER_STATE_ENABLED = 1,
+  SERIALIZER_STATE_PERMANENTLY_DISABLED = 2
+};
+
 // There can be only one serializer per V8 process.
 class Serializer : public SerializerDeserializer {
  public:
   Serializer(Isolate* isolate, SnapshotByteSink* sink);
   ~Serializer();
   void VisitPointers(Object** start, Object** end);
   // You can call this after serialization to find out how much space was used
   // in each space.
   int CurrentAllocationAddress(int space) {
     ASSERT(space < kNumberOfSpaces);
     return fullness_[space];
   }
 
   Isolate* isolate() const { return isolate_; }
   static void Enable(Isolate* isolate);
   static void Disable();
 
   // Call this when you have made use of the fact that there is no serialization
-  // going on.
-  static void TooLateToEnableNow() { too_late_to_enable_now_ = true; }
-  static bool enabled() { return serialization_enabled_; }
+  // going on. Returns true if serialization was disabled, and now it's
+  // permanetely disabled.
+  static bool TrySetPermanentlyDisabled() {
+    LockGuard<Mutex> lock_guard(&serialization_mutex_);
+    // Changes are only made under the lock.
+    if (serialization_state_ == SERIALIZER_STATE_DISABLED) {
+      serialization_state_ = SERIALIZER_STATE_PERMANENTLY_DISABLED;
+      return true;
+    }
+    return false;
+  }
+  static bool IsPermanentlyDisabled() {
+    LockGuard<Mutex> lock_guard(&serialization_mutex_);
+    return serialization_state_ ==
+        SERIALIZER_STATE_PERMANENTLY_DISABLED;
+  }
+  static bool enabled() {
+    LockGuard<Mutex> lock_guard(&serialization_mutex_);
+    return serialization_state_ == SERIALIZER_STATE_ENABLED;
+  }
   SerializationAddressMapper* address_mapper() { return &address_mapper_; }
   void PutRoot(int index,
                HeapObject* object,
                HowToCode how,
                WhereToPoint where,
                int skip);
 
  protected:
   static const int kInvalidRootIndex = -1;
 
@@ skipping 77 matching lines @@
   // Some roots should not be serialized, because their actual value depends on
   // absolute addresses and they are reset after deserialization, anyway.
   bool ShouldBeSkipped(Object** current);
 
   Isolate* isolate_;
   // Keep track of the fullness of each space in order to generate
   // relative addresses for back references.
   int fullness_[LAST_SPACE + 1];
   SnapshotByteSink* sink_;
   ExternalReferenceEncoder* external_reference_encoder_;
-  static bool serialization_enabled_;
-  // Did we already make use of the fact that serialization was not enabled?
-  static bool too_late_to_enable_now_;
+
+  static Mutex serialization_mutex_;
+  static SerializationState serialization_state_;
+
   SerializationAddressMapper address_mapper_;
   intptr_t root_index_wave_front_;
   void Pad();
 
   friend class ObjectSerializer;
   friend class Deserializer;
 
  private:
   static CodeAddressMap* code_address_map_;
   DISALLOW_COPY_AND_ASSIGN(Serializer);
@@ skipping 67 matching lines @@
  private:
   virtual bool ShouldBeInThePartialSnapshotCache(HeapObject* o) {
     return false;
   }
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_SERIALIZE_H_