Serializer enable/disable flags need thread safety.

src/serialize.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 631 matching lines @@
 }
 
 
 ExternalReferenceDecoder::~ExternalReferenceDecoder() {
   for (int type = kFirstTypeCode; type < kTypeCodeCount; ++type) {
     DeleteArray(encodings_[type]);
   }
   DeleteArray(encodings_);
 }
 
-
-bool Serializer::serialization_enabled_ = false;
-bool Serializer::too_late_to_enable_now_ = false;
-
+AtomicWord Serializer::serialization_state_ = SERIALIZER_STATE_UNINITIALIZED;
 
 class CodeAddressMap: public CodeEventLogger {
  public:
   explicit CodeAddressMap(Isolate* isolate)
       : isolate_(isolate) {
     isolate->logger()->addCodeEventListener(this);
   }
 
   virtual ~CodeAddressMap() {
     isolate_->logger()->removeCodeEventListener(this);
@@ skipping 92 matching lines @@
   }
 
   NameMap address_to_name_map_;
   Isolate* isolate_;
 };
 
 
 CodeAddressMap* Serializer::code_address_map_ = NULL;
 
 
-void Serializer::Enable(Isolate* isolate) {
-  if (!serialization_enabled_) {
-    ASSERT(!too_late_to_enable_now_);
-  }
-  if (serialization_enabled_) return;
-  serialization_enabled_ = true;
+void Serializer::RequestEnable(Isolate* isolate) {
   isolate->InitializeLoggingAndCounters();
   code_address_map_ = new CodeAddressMap(isolate);
 }
 
 
-void Serializer::Disable() {
-  if (!serialization_enabled_) return;
-  serialization_enabled_ = false;
-  delete code_address_map_;
-  code_address_map_ = NULL;
+void Serializer::InitializeOncePerProcess() {
+  // InitializeOncePerProcess is called by V8::InitializeOncePerProcess, a
+  // method guaranteed to be called only once in a process lifetime.
+  // serialization_state_ is read by many threads, hence the use of
+  // Atomic primitives. Here, we don't need a barrier or mutex to
+  // write it because V8 initialization is done by one thread, and gates
+  // all reads of serialization_state_.
+  ASSERT(NoBarrier_Load(&serialization_state_) ==
+         SERIALIZER_STATE_UNINITIALIZED);
+  SerializationState state = code_address_map_
+      ? SERIALIZER_STATE_ENABLED
+      : SERIALIZER_STATE_DISABLED;
+  NoBarrier_Store(&serialization_state_, state);
 }
 
 
+void Serializer::TearDown() {
+  // TearDown is called by V8::TearDown() for the default isolate. It's safe
+  // to shut down the serializer by that point. Just to be safe, we restore
+  // serialization_state_ to uninitialized.
+  ASSERT(NoBarrier_Load(&serialization_state_) !=
+         SERIALIZER_STATE_UNINITIALIZED);
+  if (code_address_map_) {
+    ASSERT(NoBarrier_Load(&serialization_state_) ==
+           SERIALIZER_STATE_ENABLED);
+    delete code_address_map_;
+    code_address_map_ = NULL;
+  }
+
+  NoBarrier_Store(&serialization_state_, SERIALIZER_STATE_UNINITIALIZED);
+}
+
+
 Deserializer::Deserializer(SnapshotByteSource* source)
     : isolate_(NULL),
       source_(source),
       external_reference_decoder_(NULL) {
   for (int i = 0; i < LAST_SPACE + 1; i++) {
     reservations_[i] = kUninitializedReservation;
   }
 }
 
 
@@ skipping 1087 matching lines @@
 
 bool SnapshotByteSource::AtEOF() {
   if (0u + length_ - position_ > 2 * sizeof(uint32_t)) return false;
   for (int x = position_; x < length_; x++) {
     if (data_[x] != SerializerDeserializer::nop()) return false;
   }
   return true;
 }
 
 } }  // namespace v8::internal