Introduce SynchronizedScope to allow heap access from compiler thread.

src/optimizing-compiler-thread.cc

Index: src/optimizing-compiler-thread.cc
diff --git a/src/optimizing-compiler-thread.cc b/src/optimizing-compiler-thread.cc
index d21507084c5f9d0de5d3eba72831f0f464665329..ff2995469bd83853c7f80e73e58f43c6128b0d37 100644
--- a/src/optimizing-compiler-thread.cc
+++ b/src/optimizing-compiler-thread.cc
@@ -74,7 +74,7 @@ void OptimizingCompilerThread::Run() {
       OS::Sleep(FLAG_concurrent_recompilation_delay);
     }
 
-    switch (static_cast<StopFlag>(Acquire_Load(&stop_thread_))) {
+    switch (static_cast<LoopSwitch>(Acquire_Load(&loop_switch_))) {
       case CONTINUE:
         break;
       case STOP:
@@ -86,9 +86,9 @@ void OptimizingCompilerThread::Run() {
       case FLUSH:
         // The main thread is blocked, waiting for the stop semaphore.
         { AllowHandleDereference allow_handle_dereference;
-          FlushInputQueue(true);
+          FlushInputQueue(RESTORE_FUNCTION_CODE);
         }
-        Release_Store(&stop_thread_, static_cast<AtomicWord>(CONTINUE));
+        Release_Store(&loop_switch_, static_cast<AtomicWord>(CONTINUE));
         stop_semaphore_.Signal();
         // Return to start of consumer loop.
         continue;
@@ -107,7 +107,7 @@ void OptimizingCompilerThread::Run() {
 
 
 OptimizedCompileJob* OptimizingCompilerThread::NextInput() {
-  LockGuard<Mutex> access_input_queue_(&input_queue_mutex_);
+  LockGuard<Mutex> access_input_queue_(&mutex_);
   if (input_queue_length_ == 0) return NULL;
   OptimizedCompileJob* job = input_queue_[InputQueueIndex(0)];
   ASSERT_NE(NULL, job);
@@ -134,11 +134,11 @@ void OptimizingCompilerThread::CompileNext() {
 }
 
 
-static void DisposeOptimizedCompileJob(OptimizedCompileJob* job,
-                                       bool restore_function_code) {
+void OptimizingCompilerThread::DisposeOptimizedCompileJob(
+    OptimizedCompileJob* job, FlushMode mode) {
   // The recompile job is allocated in the CompilationInfo's zone.
   CompilationInfo* info = job->info();
-  if (restore_function_code) {
+  if (mode == RESTORE_FUNCTION_CODE) {
     if (info->is_osr()) {
       if (!job->IsWaitingForInstall()) {
         // Remove stack check that guards OSR entry on original code.
@@ -155,7 +155,7 @@ static void DisposeOptimizedCompileJob(OptimizedCompileJob* job,
 }
 
 
-void OptimizingCompilerThread::FlushInputQueue(bool restore_function_code) {
+void OptimizingCompilerThread::FlushInputQueue(FlushMode mode) {
   OptimizedCompileJob* job;
   while ((job = NextInput())) {
     // This should not block, since we have one signal on the input queue
@@ -163,41 +163,61 @@ void OptimizingCompilerThread::FlushInputQueue(bool restore_function_code) {
     input_queue_semaphore_.Wait();
     // OSR jobs are dealt with separately.
     if (!job->info()->is_osr()) {
-      DisposeOptimizedCompileJob(job, restore_function_code);
+      DisposeOptimizedCompileJob(job, mode);
     }
   }
 }
 
 
-void OptimizingCompilerThread::FlushOutputQueue(bool restore_function_code) {
+void OptimizingCompilerThread::FlushOutputQueue(FlushMode mode) {
   OptimizedCompileJob* job;
   while (output_queue_.Dequeue(&job)) {
     // OSR jobs are dealt with separately.
     if (!job->info()->is_osr()) {
-      DisposeOptimizedCompileJob(job, restore_function_code);
+      DisposeOptimizedCompileJob(job, mode);
     }
   }
 }
 
 
-void OptimizingCompilerThread::FlushOsrBuffer(bool restore_function_code) {
+void OptimizingCompilerThread::FlushOsrBuffer(FlushMode mode) {
   for (int i = 0; i < osr_buffer_capacity_; i++) {
     if (osr_buffer_[i] != NULL) {
-      DisposeOptimizedCompileJob(osr_buffer_[i], restore_function_code);
+      DisposeOptimizedCompileJob(osr_buffer_[i], mode);
       osr_buffer_[i] = NULL;
     }
   }
 }
 
 
-void OptimizingCompilerThread::Flush() {
+void  OptimizingCompilerThread::SetSwitchAndInterceptInterrupt(
+    LoopSwitch loop_switch) {
+  // The compiler thread may be waiting for the main (this) thread to handle
+  // a stack check interrupt when entering a SynchronizedScope.
+  // Use a mutex when changing the loop switch and checking the stack guard
+  // state to avoid race with PauseMainThread.
+  { LockGuard<Mutex> set_switch_and_check_interrupt(&mutex_);
+    NoBarrier_Store(&loop_switch_, static_cast<AtomicWord>(loop_switch));

[Hannes Payer (out of office), 2014/03/21 12:44:31]

loop_switch_ is accessed with NoBarrier and Acquire/Release operations. I think
we should figure out what mode is required and converge into one mode. I guess
it is Acquire/Release.

[Yang, 2014/03/21 13:01:06]

For the record, I was thinking the mutex scope would pose a global barrier. But
I guess Acquire/Release wouldn't hurt.

+    if (!isolate_->stack_guard()->IsCompilerSyncRequest()) return;
+  }
+  isolate_->stack_guard()->Continue(COMPILER_SYNC);
+  YieldToCompilerThread();
+}
+
+
+void OptimizingCompilerThread::PrepareInterruption(LoopSwitch loop_switch) {
   ASSERT(!IsOptimizerThread());
-  Release_Store(&stop_thread_, static_cast<AtomicWord>(FLUSH));
   if (FLAG_block_concurrent_recompilation) Unblock();
+  SetSwitchAndInterceptInterrupt(loop_switch);
   input_queue_semaphore_.Signal();
   stop_semaphore_.Wait();
-  FlushOutputQueue(true);
-  if (FLAG_concurrent_osr) FlushOsrBuffer(true);
+}
+
+
+void OptimizingCompilerThread::Flush() {
+  PrepareInterruption(FLUSH);
+  FlushOutputQueue(RESTORE_FUNCTION_CODE);
+  if (FLAG_concurrent_osr) FlushOsrBuffer(RESTORE_FUNCTION_CODE);
   if (FLAG_trace_concurrent_recompilation) {
     PrintF("  ** Flushed concurrent recompilation queues.\n");
   }
@@ -205,23 +225,18 @@ void OptimizingCompilerThread::Flush() {
 
 
 void OptimizingCompilerThread::Stop() {
-  ASSERT(!IsOptimizerThread());
-  Release_Store(&stop_thread_, static_cast<AtomicWord>(STOP));
-  if (FLAG_block_concurrent_recompilation) Unblock();
-  input_queue_semaphore_.Signal();
-  stop_semaphore_.Wait();
-
+  PrepareInterruption(STOP);
   if (FLAG_concurrent_recompilation_delay != 0) {
     // At this point the optimizing compiler thread's event loop has stopped.
     // There is no need for a mutex when reading input_queue_length_.
     while (input_queue_length_ > 0) CompileNext();
     InstallOptimizedFunctions();
   } else {
-    FlushInputQueue(false);
-    FlushOutputQueue(false);
+    FlushInputQueue(DO_NOT_RESTORE_FUNCTION_CODE);
+    FlushOutputQueue(DO_NOT_RESTORE_FUNCTION_CODE);
   }
 
-  if (FLAG_concurrent_osr) FlushOsrBuffer(false);
+  if (FLAG_concurrent_osr) FlushOsrBuffer(DO_NOT_RESTORE_FUNCTION_CODE);
 
   if (FLAG_trace_concurrent_recompilation) {
     double percentage = time_spent_compiling_.PercentOf(time_spent_total_);
@@ -274,7 +289,7 @@ void OptimizingCompilerThread::QueueForOptimization(OptimizedCompileJob* job) {
     osr_attempts_++;
     AddToOsrBuffer(job);
     // Add job to the front of the input queue.
-    LockGuard<Mutex> access_input_queue(&input_queue_mutex_);
+    LockGuard<Mutex> access_input_queue(&mutex_);
     ASSERT_LT(input_queue_length_, input_queue_capacity_);
     // Move shift_ back by one.
     input_queue_shift_ = InputQueueIndex(input_queue_capacity_ - 1);
@@ -282,7 +297,7 @@ void OptimizingCompilerThread::QueueForOptimization(OptimizedCompileJob* job) {
     input_queue_length_++;
   } else {
     // Add job to the back of the input queue.
-    LockGuard<Mutex> access_input_queue(&input_queue_mutex_);
+    LockGuard<Mutex> access_input_queue(&mutex_);
     ASSERT_LT(input_queue_length_, input_queue_capacity_);
     input_queue_[InputQueueIndex(input_queue_length_)] = job;
     input_queue_length_++;
@@ -366,13 +381,59 @@ void OptimizingCompilerThread::AddToOsrBuffer(OptimizedCompileJob* job) {
       info->closure()->PrintName();
       PrintF(", AST id %d]\n", info->osr_ast_id().ToInt());
     }
-    DisposeOptimizedCompileJob(stale, false);
+    DisposeOptimizedCompileJob(stale, DO_NOT_RESTORE_FUNCTION_CODE);
   }
   osr_buffer_[osr_buffer_cursor_] = job;
   osr_buffer_cursor_ = (osr_buffer_cursor_ + 1) % osr_buffer_capacity_;
 }
 
 
+void OptimizingCompilerThread::PauseMainThread() {
+  ASSERT(IsOptimizerThread());
+  // Request a stack check interrupt if we are not flushing or stopping.
+  // Make sure the state does not change after the check using a mutex.
+  { LockGuard<Mutex> check_switch_and_set_interrupt(&mutex_);
+    if (static_cast<LoopSwitch>(NoBarrier_Load(&loop_switch_)) != CONTINUE) {
+      return;
+    }
+    isolate_->stack_guard()->RequestCompilerSync();
+  }
+  compiler_thread_semaphore_.Wait();
+}
+
+
+void OptimizingCompilerThread::ContinueMainThread() {
+  ASSERT(IsOptimizerThread());
+  main_thread_semaphore_.Signal();
+}
+
+
+void OptimizingCompilerThread::YieldToCompilerThread() {
+  ASSERT(!IsOptimizerThread());
+  Logger::TimerEventScope scope(
+      isolate_, Logger::TimerEventScope::v8_recompile_synchronized);
+  compiler_thread_semaphore_.Signal();
+  main_thread_semaphore_.Wait();
+}
+
+
+OptimizingCompilerThread::SynchronizedScope::SynchronizedScope(
+    CompilationInfo* info) : info_(info) {
+  Isolate* isolate = info_->isolate();
+  if (isolate->concurrent_recompilation_enabled() && info_->is_concurrent()) {
+    isolate->optimizing_compiler_thread()->PauseMainThread();
+  }
+}
+
+
+OptimizingCompilerThread::SynchronizedScope::~SynchronizedScope() {
+  Isolate* isolate = info_->isolate();
+  if (isolate->concurrent_recompilation_enabled() && info_->is_concurrent()) {
+    isolate->optimizing_compiler_thread()->ContinueMainThread();
+  }
+}
+
+
 #ifdef DEBUG
 bool OptimizingCompilerThread::IsOptimizerThread(Isolate* isolate) {
   return isolate->concurrent_recompilation_enabled() &&