Fix data race in v8::internal::UnboundQueue

src/optimizing-compiler-thread.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 110 matching lines @@
     double percentage = (compile_time * 100) / total_time;
     PrintF("  ** Compiler thread did %.2f%% useful work\n", percentage);
   }
 }
 
 
 void OptimizingCompilerThread::InstallOptimizedFunctions() {
   ASSERT(!IsOptimizerThread());
   HandleScope handle_scope(isolate_);
   int functions_installed = 0;
-  while (!output_queue_.IsEmpty()) {
-    OptimizingCompiler* compiler;
-    output_queue_.Dequeue(&compiler);
+  OptimizingCompiler* compiler;
+  while (output_queue_.Dequeue(&compiler)) {
     Compiler::InstallOptimizedCode(compiler);
     functions_installed++;
   }
 }
 
 
 void OptimizingCompilerThread::QueueForOptimization(
     OptimizingCompiler* optimizing_compiler) {
   ASSERT(IsQueueAvailable());
   ASSERT(!IsOptimizerThread());
   Barrier_AtomicIncrement(&queue_length_, static_cast<Atomic32>(1));
   optimizing_compiler->info()->closure()->MarkInRecompileQueue();
   input_queue_.Enqueue(optimizing_compiler);
   input_queue_semaphore_->Signal();
 }
 
 
 #ifdef DEBUG
 bool OptimizingCompilerThread::IsOptimizerThread() {
   if (!FLAG_parallel_recompilation) return false;
   return ThreadId::Current().ToInteger() == thread_id_;
 }
 #endif
 
 
 } }  // namespace v8::internal