Switch profiler from isolates to threads [second landing]

runtime/vm/thread_interrupter.cc

Index: runtime/vm/thread_interrupter.cc
diff --git a/runtime/vm/thread_interrupter.cc b/runtime/vm/thread_interrupter.cc
index 0b0471b39e58918878b1ed977d5721224e94ed1b..8a8af044fce87fd942b2c2fa66d1a8045ba3e910 100644
--- a/runtime/vm/thread_interrupter.cc
+++ b/runtime/vm/thread_interrupter.cc
@@ -51,6 +51,7 @@ DEFINE_FLAG(bool, trace_thread_interrupter, false,
 bool ThreadInterrupter::initialized_ = false;
 bool ThreadInterrupter::shutdown_ = false;
 bool ThreadInterrupter::thread_running_ = false;
+bool ThreadInterrupter::woken_up_ = false;
 ThreadJoinId ThreadInterrupter::interrupter_thread_id_ =
     OSThread::kInvalidThreadJoinId;
 Monitor* ThreadInterrupter::monitor_ = NULL;
@@ -125,9 +126,14 @@ void ThreadInterrupter::SetInterruptPeriod(intptr_t period) {
 
 
 void ThreadInterrupter::WakeUp() {
+  if (!initialized_) {
+    // Early call.
+    return;
+  }
   ASSERT(initialized_);
   {
     MonitorLocker ml(monitor_);
+    woken_up_ = true;
     if (!InDeepSleep()) {
       // No need to notify, regularly waking up.
       return;
@@ -138,35 +144,6 @@ void ThreadInterrupter::WakeUp() {
 }
 
 
-void ThreadInterruptNoOp(const InterruptedThreadState& state, void* data) {
-  // NoOp.
-}
-
-
-class ThreadInterrupterVisitIsolates : public IsolateVisitor {
- public:
-  ThreadInterrupterVisitIsolates() {
-    profiled_thread_count_ = 0;
-  }
-
-  void VisitIsolate(Isolate* isolate) {
-    ASSERT(isolate != NULL);
-    profiled_thread_count_ += isolate->ProfileInterrupt();
-  }
-
-  intptr_t profiled_thread_count() const {
-    return profiled_thread_count_;
-  }
-
-  void set_profiled_thread_count(intptr_t profiled_thread_count) {
-    profiled_thread_count_ = profiled_thread_count;
-  }
-
- private:
-  intptr_t profiled_thread_count_;
-};
-
-
 void ThreadInterrupter::ThreadMain(uword parameters) {
   ASSERT(initialized_);
   InstallSignalHandler();
@@ -181,35 +158,55 @@ void ThreadInterrupter::ThreadMain(uword parameters) {
     startup_ml.Notify();
   }
   {
-    ThreadInterrupterVisitIsolates visitor;
+    intptr_t interrupted_thread_count = 0;
     current_wait_time_ = interrupt_period_;
     MonitorLocker wait_ml(monitor_);
     while (!shutdown_) {
       intptr_t r = wait_ml.WaitMicros(current_wait_time_);
 
-      if ((r == Monitor::kNotified) && shutdown_) {
+      if (shutdown_) {
         break;
       }
 
       if ((r == Monitor::kNotified) && InDeepSleep()) {
         // Woken up from deep sleep.
-        ASSERT(visitor.profiled_thread_count() == 0);
+        ASSERT(interrupted_thread_count == 0);
         // Return to regular interrupts.
         current_wait_time_ = interrupt_period_;
       }
 
-      // Reset count before visiting isolates.
-      visitor.set_profiled_thread_count(0);
-      Isolate::VisitIsolates(&visitor);
+      // Reset count before interrupting any threads.
+      interrupted_thread_count = 0;
+
+      // Temporarily drop the monitor while we interrupt threads.
+      monitor_->Exit();
+
+      {
+        ThreadIterator it;
+        while (it.HasNext()) {
+          Thread* thread = it.Next();
+          if (thread->ThreadInterruptsEnabled()) {
+            interrupted_thread_count++;
+            InterruptThread(thread);
+          }
+        }
+      }
+
+      // Take the monitor lock again.
+      monitor_->Enter();
 
-      if (visitor.profiled_thread_count() == 0) {
-        // No isolates were profiled. In order to reduce unnecessary CPU
-        // load, we will wait until we are notified before attempting to
-        // interrupt again.
+      // Now that we have the lock, check if we were signaled to wake up while
+      // interrupting threads.
+      if (!woken_up_ && (interrupted_thread_count == 0)) {
+        // No threads were interrupted and we were not signaled to interrupt
+        // new threads. In order to reduce unnecessary CPU load, we will wait
+        // until we are notified before attempting to interrupt again.
         current_wait_time_ = Monitor::kNoTimeout;
         continue;
       }
 
+      woken_up_ = false;
+
       ASSERT(current_wait_time_ != Monitor::kNoTimeout);
     }
   }