[simulator] Make reference redirection thread-safe.

src/ppc/simulator-ppc.cc

 // Copyright 2014 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 <stdarg.h>
 #include <stdlib.h>
 #include <cmath>
 
 #if V8_TARGET_ARCH_PPC
 
@@ skipping 876 matching lines @@
       delete static_cast<CachePage*>(entry->value);
     }
     delete i_cache;
   }
 }
 
 
 void* Simulator::RedirectExternalReference(Isolate* isolate,
                                            void* external_function,
                                            ExternalReference::Type type) {
+  base::LockGuard<base::Mutex> lock_guard(
+      isolate->simulator_redirection_mutex());
   Redirection* redirection = Redirection::Get(isolate, external_function, type);
   return redirection->address();
 }
 
 
 // Get the active Simulator for the current thread.
 Simulator* Simulator::current(Isolate* isolate) {
   v8::internal::Isolate::PerIsolateThreadData* isolate_data =
       isolate->FindOrAllocatePerThreadDataForThisThread();
   DCHECK(isolate_data != NULL);
@@ skipping 3523 matching lines @@
   }
   processor->prev_ = nullptr;
   processor->next_ = nullptr;
 }
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // USE_SIMULATOR
 #endif  // V8_TARGET_ARCH_PPC