Fix data race with interface caching

src/interface.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/v8.h"
 
 #include "src/interface.h"
 
+#include "src/base/lazy-instance.h"
+
 namespace v8 {
 namespace internal {
 
+// ---------------------------------------------------------------------------
+// Initialization.
+
+struct Interface::ValueCreate {
+  static void Construct(Interface* ptr) {
+    ::new (ptr) Interface(VALUE + FROZEN);
+  }
+};
+
+
+struct Interface::ConstCreate {
+  static void Construct(Interface* ptr) {
+    ::new (ptr) Interface(VALUE + CONST + FROZEN);
+  }
+};
+
+
+namespace {
+  base::LazyInstance<Interface, Interface::ValueCreate>::type value_interface =
+      LAZY_INSTANCE_INITIALIZER;
+
+  base::LazyInstance<Interface, Interface::ConstCreate>::type const_interface =
+      LAZY_INSTANCE_INITIALIZER;
+}
+
+
+Interface* Interface::NewValue() {
+  return value_interface.Pointer();  // Cached.
+}
+
+
+Interface* Interface::NewConst() {
+  return const_interface.Pointer();  // Cached.
+}
+
+
+// ---------------------------------------------------------------------------
+// Lookup.
+
 Interface* Interface::Lookup(Handle<String> name, Zone* zone) {
   DCHECK(IsModule());
   ZoneHashMap* map = Chase()->exports_;
-  if (map == NULL) return NULL;
+  if (map == nullptr) return nullptr;
   ZoneAllocationPolicy allocator(zone);
-  ZoneHashMap::Entry* p = map->Lookup(name.location(), name->Hash(), false,
-                                      allocator);
-  if (p == NULL) return NULL;
+  ZoneHashMap::Entry* p =
+      map->Lookup(name.location(), name->Hash(), false, allocator);
+  if (p == nullptr) return nullptr;
   DCHECK(*static_cast<String**>(p->key) == *name);
-  DCHECK(p->value != NULL);
+  DCHECK(p->value != nullptr);
   return static_cast<Interface*>(p->value);
 }
 
 
+// ---------------------------------------------------------------------------
+// Addition.
+
 #ifdef DEBUG
 // Current nesting depth for debug output.
 class Nesting {
  public:
   Nesting()  { current_ += 2; }
   ~Nesting() { current_ -= 2; }
   static int current() { return current_; }
  private:
   static int current_;
 };
 
 int Nesting::current_ = 0;
 #endif
 
 
 void Interface::DoAdd(const void* name, uint32_t hash, Interface* interface,
                       Zone* zone, bool* ok) {
   MakeModule(ok);
   if (!*ok) return;
 
 #ifdef DEBUG
   if (FLAG_print_interface_details) {
     PrintF("%*s# Adding...\n", Nesting::current(), "");
     PrintF("%*sthis = ", Nesting::current(), "");
     this->Print(Nesting::current());
-    const AstRawString* symbol = static_cast<const AstRawString*>(name);
-    PrintF("%*s%.*s : ", Nesting::current(), "", symbol->length(),
-           symbol->raw_data());
+    const AstRawString* raw = static_cast<const AstRawString*>(name);
+    PrintF("%*s%.*s : ", Nesting::current(), "",
+           raw->length(), raw->raw_data());
     interface->Print(Nesting::current());
   }
 #endif
 
   ZoneHashMap** map = &Chase()->exports_;
   ZoneAllocationPolicy allocator(zone);
 
-  if (*map == NULL) {
+  if (*map == nullptr) {
     *map = new(zone->New(sizeof(ZoneHashMap)))
         ZoneHashMap(ZoneHashMap::PointersMatch,
                     ZoneHashMap::kDefaultHashMapCapacity, allocator);
   }
 
   ZoneHashMap::Entry* p =
       (*map)->Lookup(const_cast<void*>(name), hash, !IsFrozen(), allocator);
-  if (p == NULL) {
+  if (p == nullptr) {
     // This didn't have name but was frozen already, that's an error.
     *ok = false;
-  } else if (p->value == NULL) {
+  } else if (p->value == nullptr) {
     p->value = interface;
   } else {
 #ifdef DEBUG
     Nesting nested;
 #endif
     static_cast<Interface*>(p->value)->Unify(interface, zone, ok);
   }
 
 #ifdef DEBUG
   if (FLAG_print_interface_details) {
     PrintF("%*sthis' = ", Nesting::current(), "");
     this->Print(Nesting::current());
     PrintF("%*s# Added.\n", Nesting::current(), "");
   }
 #endif
 }
 
 
+// ---------------------------------------------------------------------------
+// Unification.
+
 void Interface::Unify(Interface* that, Zone* zone, bool* ok) {
   if (this->forward_) return this->Chase()->Unify(that, zone, ok);
   if (that->forward_) return this->Unify(that->Chase(), zone, ok);
-  DCHECK(this->forward_ == NULL);
-  DCHECK(that->forward_ == NULL);
+  DCHECK(this->forward_ == nullptr);
+  DCHECK(that->forward_ == nullptr);
 
   *ok = true;
   if (this == that) return;
   if (this->IsValue()) {
     that->MakeValue(ok);
     if (*ok && this->IsConst()) that->MakeConst(ok);
     return;
   }
   if (that->IsValue()) {
     this->MakeValue(ok);
     if (*ok && that->IsConst()) this->MakeConst(ok);
     return;
   }
 
 #ifdef DEBUG
   if (FLAG_print_interface_details) {
     PrintF("%*s# Unifying...\n", Nesting::current(), "");
     PrintF("%*sthis = ", Nesting::current(), "");
     this->Print(Nesting::current());
     PrintF("%*sthat = ", Nesting::current(), "");
     that->Print(Nesting::current());
   }
 #endif
 
   // Merge the smaller interface into the larger, for performance.
-  if (this->exports_ != NULL && (that->exports_ == NULL ||
+  if (this->exports_ != nullptr && (that->exports_ == nullptr ||
       this->exports_->occupancy() >= that->exports_->occupancy())) {
     this->DoUnify(that, ok, zone);
   } else {
     that->DoUnify(this, ok, zone);
   }
 
 #ifdef DEBUG
   if (FLAG_print_interface_details) {
     PrintF("%*sthis' = ", Nesting::current(), "");
     this->Print(Nesting::current());
     PrintF("%*sthat' = ", Nesting::current(), "");
     that->Print(Nesting::current());
     PrintF("%*s# Unified.\n", Nesting::current(), "");
   }
 #endif
 }
 
 
 void Interface::DoUnify(Interface* that, bool* ok, Zone* zone) {
-  DCHECK(this->forward_ == NULL);
-  DCHECK(that->forward_ == NULL);
+  DCHECK(this->forward_ == nullptr);
+  DCHECK(that->forward_ == nullptr);
   DCHECK(!this->IsValue());
   DCHECK(!that->IsValue());
   DCHECK(this->index_ == -1);
   DCHECK(that->index_ == -1);
   DCHECK(*ok);
 
 #ifdef DEBUG
     Nesting nested;
 #endif
 
   // Try to merge all members from that into this.
   ZoneHashMap* map = that->exports_;
-  if (map != NULL) {
-    for (ZoneHashMap::Entry* p = map->Start(); p != NULL; p = map->Next(p)) {
+  if (map != nullptr) {
+    for (ZoneHashMap::Entry* p = map->Start(); p != nullptr; p = map->Next(p)) {
       this->DoAdd(p->key, p->hash, static_cast<Interface*>(p->value), zone, ok);
       if (!*ok) return;
     }
   }
 
   // If the new interface is larger than that's, then there were members in
   // 'this' which 'that' didn't have. If 'that' was frozen that is an error.
-  int this_size = this->exports_ == NULL ? 0 : this->exports_->occupancy();
-  int that_size = map == NULL ? 0 : map->occupancy();
+  int this_size = this->exports_ == nullptr ? 0 : this->exports_->occupancy();
+  int that_size = map == nullptr ? 0 : map->occupancy();
   if (that->IsFrozen() && this_size > that_size) {
     *ok = false;
     return;
   }
 
   // Merge interfaces.
   this->flags_ |= that->flags_;
   that->forward_ = this;
 }
 
 
+// ---------------------------------------------------------------------------
+// Printing.
+
 #ifdef DEBUG
 void Interface::Print(int n) {
   int n0 = n > 0 ? n : 0;
 
   if (FLAG_print_interface_details) {
     PrintF("%p", static_cast<void*>(this));
-    for (Interface* link = this->forward_; link != NULL; link = link->forward_)
+    for (Interface* link = this->forward_; link != nullptr;
+        link = link->forward_) {
       PrintF("->%p", static_cast<void*>(link));
+    }
     PrintF(" ");
   }
 
   if (IsUnknown()) {
     PrintF("unknown\n");
   } else if (IsConst()) {
     PrintF("const\n");
   } else if (IsValue()) {
     PrintF("value\n");
   } else if (IsModule()) {
     PrintF("module %d %s{", Index(), IsFrozen() ? "" : "(unresolved) ");
     ZoneHashMap* map = Chase()->exports_;
-    if (map == NULL || map->occupancy() == 0) {
+    if (map == nullptr || map->occupancy() == 0) {
       PrintF("}\n");
     } else if (n < 0 || n0 >= 2 * FLAG_print_interface_depth) {
       // Avoid infinite recursion on cyclic types.
       PrintF("...}\n");
     } else {
       PrintF("\n");
-      for (ZoneHashMap::Entry* p = map->Start(); p != NULL; p = map->Next(p)) {
+      for (ZoneHashMap::Entry* p = map->Start();
+           p != nullptr; p = map->Next(p)) {
         String* name = *static_cast<String**>(p->key);
         Interface* interface = static_cast<Interface*>(p->value);
         PrintF("%*s%s : ", n0 + 2, "", name->ToAsciiArray());
         interface->Print(n0 + 2);
       }
       PrintF("%*s}\n", n0, "");
     }
   }
 }
 #endif
 
 } }  // namespace v8::internal