Use mutex instead of busy wait when installing optimized function.

R=jkummerow@chromium.org
BUG=

Review URL: https://codereview.chromium.org/17099012

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@15262 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/optimizing-compiler-thread.cc

@@ -89,8 +89,9 @@ void OptimizingCompilerThread::CompileNext() {
   ASSERT(status != OptimizingCompiler::FAILED);
 
   // The function may have already been optimized by OSR.  Simply continue.
-  // Mark it for installing before queuing so that we can be sure of the write
-  // order: marking first and (after being queued) installing code second.
+  // Use a mutex to make sure that functions marked for install
+  // are always also queued.
+  ScopedLock mark_and_queue(install_mutex_);
   { Heap::RelocationLock relocation_lock(isolate_->heap());
     AllowHandleDereference ahd;
     optimizing_compiler->info()->closure()->MarkForInstallingRecompiledCode();
@@ -130,11 +131,13 @@ void OptimizingCompilerThread::Stop() {
 void OptimizingCompilerThread::InstallOptimizedFunctions() {
   ASSERT(!IsOptimizerThread());
   HandleScope handle_scope(isolate_);
-  int functions_installed = 0;
   OptimizingCompiler* compiler;
-  while (output_queue_.Dequeue(&compiler)) {
+  while (true) {
+    { // Memory barrier to ensure marked functions are queued.
+      ScopedLock marked_and_queued(install_mutex_);
+      if (!output_queue_.Dequeue(&compiler)) return;
+    }
     Compiler::InstallOptimizedCode(compiler);
-    functions_installed++;
   }
 }
 

src/optimizing-compiler-thread.h

@@ -50,6 +50,7 @@ class OptimizingCompilerThread : public Thread {
       isolate_(isolate),
       stop_semaphore_(OS::CreateSemaphore(0)),
       input_queue_semaphore_(OS::CreateSemaphore(0)),
+      install_mutex_(OS::CreateMutex()),
       time_spent_compiling_(0),
       time_spent_total_(0) {
     NoBarrier_Store(&stop_thread_, static_cast<AtomicWord>(false));
@@ -95,6 +96,7 @@ class OptimizingCompilerThread : public Thread {
   Semaphore* input_queue_semaphore_;
   UnboundQueue<OptimizingCompiler*> input_queue_;
   UnboundQueue<OptimizingCompiler*> output_queue_;
+  Mutex* install_mutex_;
   volatile AtomicWord stop_thread_;
   volatile Atomic32 queue_length_;
   int64_t time_spent_compiling_;

src/runtime.cc

@@ -7912,12 +7912,7 @@ RUNTIME_FUNCTION(MaybeObject*, Runtime_InstallRecompiledCode) {
   ASSERT(args.length() == 1);
   CONVERT_ARG_HANDLE_CHECKED(JSFunction, function, 0);
   ASSERT(V8::UseCrankshaft() && FLAG_parallel_recompilation);
-  OptimizingCompilerThread* opt_thread = isolate->optimizing_compiler_thread();
-  do {
-    // The function could have been marked for installing, but not queued just
-    // yet.  In this case, retry until installed.
-    opt_thread->InstallOptimizedFunctions();
-  } while (function->IsMarkedForInstallingRecompiledCode());
+  isolate->optimizing_compiler_thread()->InstallOptimizedFunctions();
   return function->code();
 }