Fix data race with interface caching

src/interface.h

 // 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.
 
 #ifndef V8_INTERFACE_H_
 #define V8_INTERFACE_H_
 
 #include "src/ast-value-factory.h"
+#include "src/base/lazy-instance.h"

[Benedikt Meurer, 2014/10/21 04:09:05]

No need for this include, see comment below.

 #include "src/zone-inl.h"  // For operator new.
 
 namespace v8 {
 namespace internal {
 
 
 // This class implements the following abstract grammar of interfaces
 // (i.e. module types):
 //   interface ::= UNDETERMINED | VALUE | CONST | MODULE(exports)
 //   exports ::= {name : interface, ...}
@@ skipping 15 matching lines @@
 
 class Interface : public ZoneObject {
  public:
   // ---------------------------------------------------------------------------
   // Factory methods.
 
   static Interface* NewUnknown(Zone* zone) {
     return new(zone) Interface(NONE);
   }
 
-  static Interface* NewValue() {
-    static Interface value_interface(VALUE + FROZEN);  // Cached.
-    return &value_interface;
-  }
+  static Interface* NewValue();
 
-  static Interface* NewConst() {
-    static Interface value_interface(VALUE + CONST + FROZEN);  // Cached.
-    return &value_interface;
-  }
+  static Interface* NewConst();
 
   static Interface* NewModule(Zone* zone) {
     return new(zone) Interface(MODULE);
   }
 
   // ---------------------------------------------------------------------------
   // Mutators.
 
   // Add a name to the list of exports. If it already exists, unify with
   // interface, otherwise insert unless this is closed.
@@ skipping 132 matching lines @@
     : flags_(flags),
       forward_(NULL),
       exports_(NULL),
       index_(-1) {
 #ifdef DEBUG
     if (FLAG_print_interface_details)
       PrintF("# Creating %p\n", static_cast<void*>(this));
 #endif
   }
 
+  struct ValueCreate;
+  struct ConstCreate;
+  static base::LazyInstance<Interface*, ValueCreate>::type value_interface_;

[Benedikt Meurer, 2014/10/21 04:09:05]

Move the statics to the .cc file and hide them in namespace { }, i.e.

namespace {

base::LayzInstance<Interface*, Interface::ValueCreate>::type kValueInterface =
LAZY_INSTANCE_INITIALIZER;


base::LayzInstance<Interface*, Interface::ValueCreate>::type kConstInterface =
LAZY_INSTANCE_INITIALIZER;

}

[rossberg, 2014/10/21 10:42:52]

Done. Also changed them to do in-place construction.

+  static base::LazyInstance<Interface*, ConstCreate>::type const_interface_;
+
   Interface* Chase() {
     Interface* result = this;
     while (result->forward_ != NULL) result = result->forward_;
     if (result != this) forward_ = result;  // On-the-fly path compression.
     return result;
   }
 
   void DoAdd(const void* name, uint32_t hash, Interface* interface, Zone* zone,
              bool* ok);
   void DoUnify(Interface* that, bool* ok, Zone* zone);
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_INTERFACE_H_