Re-reland "Flush parallel recompilation queues on context dispose notification"

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 42 matching lines @@
 
   while (true) {
     input_queue_semaphore_->Wait();
     Logger::TimerEventScope timer(
         isolate_, Logger::TimerEventScope::v8_recompile_parallel);
 
     if (FLAG_parallel_recompilation_delay != 0) {
       OS::Sleep(FLAG_parallel_recompilation_delay);
     }
 
-    if (Acquire_Load(&stop_thread_)) {
-      stop_semaphore_->Signal();
-      if (FLAG_trace_parallel_recompilation) {
-        time_spent_total_ = OS::Ticks() - epoch;
-      }
-      return;
+    switch (static_cast<StopFlag>(Acquire_Load(&stop_thread_))) {
+      case CONTINUE:
+        break;
+      case STOP:
+        if (FLAG_trace_parallel_recompilation) {
+          time_spent_total_ = OS::Ticks() - epoch;
+        }
+        stop_semaphore_->Signal();
+        return;
+      case FLUSH:
+        // The main thread is blocked, waiting for the stop semaphore.
+        { AllowHandleDereference allow_handle_dereference;
+          FlushInputQueue(true);
+        }
+        NoBarrier_Store(&queue_length_, static_cast<AtomicWord>(0));

[Hannes Payer (out of office), 2013/08/07 09:17:32]

I think we need a memory barrier for both stores on ARM. WDYT?

+        NoBarrier_Store(&stop_thread_, static_cast<AtomicWord>(CONTINUE));
+        stop_semaphore_->Signal();
+        // Return to start of consumer loop.
+        continue;
     }
 
     int64_t compiling_start = 0;
     if (FLAG_trace_parallel_recompilation) compiling_start = OS::Ticks();
 
     CompileNext();
 
     if (FLAG_trace_parallel_recompilation) {
       time_spent_compiling_ += OS::Ticks() - compiling_start;
     }
   }
 }
 
 
 void OptimizingCompilerThread::CompileNext() {
   OptimizingCompiler* optimizing_compiler = NULL;
-  input_queue_.Dequeue(&optimizing_compiler);
+  bool result = input_queue_.Dequeue(&optimizing_compiler);
+  USE(result);
+  ASSERT(result);
   Barrier_AtomicIncrement(&queue_length_, static_cast<Atomic32>(-1));
 
   // The function may have already been optimized by OSR.  Simply continue.
   OptimizingCompiler::Status status = optimizing_compiler->OptimizeGraph();
   USE(status);   // Prevent an unused-variable error in release mode.
   ASSERT(status != OptimizingCompiler::FAILED);
 
   // The function may have already been optimized by OSR.  Simply continue.
   // 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();
   }
   output_queue_.Enqueue(optimizing_compiler);
 }
 
 
+void OptimizingCompilerThread::FlushInputQueue(bool restore_function_code) {
+  OptimizingCompiler* optimizing_compiler;
+  // The optimizing compiler is allocated in the CompilationInfo's zone.
+  while (input_queue_.Dequeue(&optimizing_compiler)) {
+    // This should not block, since we have one signal on the input queue
+    // semaphore corresponding to each element in the input queue.
+    input_queue_semaphore_->Wait();
+    CompilationInfo* info = optimizing_compiler->info();
+    if (restore_function_code) {
+      Handle<JSFunction> function = info->closure();
+      function->ReplaceCode(function->shared()->code());
+    }
+    delete info;
+  }
+}
+
+
+void OptimizingCompilerThread::FlushOutputQueue(bool restore_function_code) {
+  OptimizingCompiler* optimizing_compiler;
+  // The optimizing compiler is allocated in the CompilationInfo's zone.
+  while (output_queue_.Dequeue(&optimizing_compiler)) {
+    CompilationInfo* info = optimizing_compiler->info();
+    if (restore_function_code) {
+      AllowHandleDereference allow_handle_dereference;
+      Handle<JSFunction> function = info->closure();
+      function->ReplaceCode(function->shared()->code());
+    }
+    delete info;
+  }
+}
+
+
+void OptimizingCompilerThread::Flush() {
+  ASSERT(!IsOptimizerThread());
+  Release_Store(&stop_thread_, static_cast<AtomicWord>(FLUSH));
+  input_queue_semaphore_->Signal();
+  stop_semaphore_->Wait();
+  FlushOutputQueue(true);
+}
+
+
 void OptimizingCompilerThread::Stop() {
   ASSERT(!IsOptimizerThread());
-  Release_Store(&stop_thread_, static_cast<AtomicWord>(true));
+  Release_Store(&stop_thread_, static_cast<AtomicWord>(STOP));
   input_queue_semaphore_->Signal();
   stop_semaphore_->Wait();
 
   if (FLAG_parallel_recompilation_delay != 0) {
     // Barrier when loading queue length is not necessary since the write
     // happens in CompileNext on the same thread.
+    // This is used only for testing.
     while (NoBarrier_Load(&queue_length_) > 0) CompileNext();
     InstallOptimizedFunctions();
   } else {
-    OptimizingCompiler* optimizing_compiler;
-    // The optimizing compiler is allocated in the CompilationInfo's zone.
-    while (input_queue_.Dequeue(&optimizing_compiler)) {
-      delete optimizing_compiler->info();
-    }
-    while (output_queue_.Dequeue(&optimizing_compiler)) {
-      delete optimizing_compiler->info();
-    }
+    FlushInputQueue(false);
+    FlushOutputQueue(false);
   }
 
   if (FLAG_trace_parallel_recompilation) {
     double compile_time = static_cast<double>(time_spent_compiling_);
     double total_time = static_cast<double>(time_spent_total_);
     double percentage = (compile_time * 100) / total_time;
     PrintF("  ** Compiler thread did %.2f%% useful work\n", percentage);
   }
 
   Join();
@@ skipping 28 matching lines @@
 #ifdef DEBUG
 bool OptimizingCompilerThread::IsOptimizerThread() {
   if (!FLAG_parallel_recompilation) return false;
   ScopedLock lock(thread_id_mutex_);
   return ThreadId::Current().ToInteger() == thread_id_;
 }
 #endif
 
 
 } }  // namespace v8::internal