Reimplement Windows Monitors.

runtime/platform/thread_win.h

Index: runtime/platform/thread_win.h
diff --git a/runtime/platform/thread_win.h b/runtime/platform/thread_win.h
index 02165df2fa7c2c04a0238762d055df97b6a170a9..b481cec0f63dc5b11967e197763d9ac186559ac9 100644
--- a/runtime/platform/thread_win.h
+++ b/runtime/platform/thread_win.h
@@ -48,29 +48,53 @@ class MutexData {
 };
 
 
+class MonitorWaitData {
+ private:
+  explicit MonitorWaitData(HANDLE event) : event_(event), next_(NULL) {}
+
+  // ThreadLocalKey used to fetch and store the MonitorWaitData object
+  // for a given thread.
+  static ThreadLocalKey monitor_wait_data_key_;
+
+  // Auto-reset event used for waiting.
+  HANDLE event_;
+  // Link to next element in the singly-linked list of waiters.
+  MonitorWaitData* next_;
+
+  friend class Monitor;
+  friend class MonitorData;
+
+  DISALLOW_COPY_AND_ASSIGN(MonitorWaitData);
+};
+
+
 class MonitorData {
  private:
   MonitorData() {}
   ~MonitorData() {}
 
+  // Helper methods to manipulate the list of waiters for this
+  // monitor.
+  void AddWaiter(MonitorWaitData* wait_data);
+  void RemoveWaiter(MonitorWaitData* wait_data);
+  void SignalAndRemoveFirstWaiter();
+  void SignalAndRemoveAllWaiters();
+  MonitorWaitData* GetMonitorWaitDataForThread();
+
+  // The external critical section for the monitor.
   CRITICAL_SECTION cs_;
 
   // Condition variables are only available since Windows Vista. To
   // support at least Windows XP, we implement our own condition
   // variables using SetEvent on Event objects.
 
-  // The notify_event_ is an auto-reset event which means that
-  // SetEvent only wakes up one waiter.
-  HANDLE notify_event_;
-
-  // The notify_all_event_ is a manual-reset event which means that
-  // SetEvent wakes up all waiters.
-  HANDLE notify_all_event_;
-
-  // Counter with protection used to determine the right time to reset
-  // the notify_all_event_.
+  // Singly-linked list of event objects, one for each thread waiting
+  // on this monitor. New waiters are added at the end of the list.
+  // Notify signals the first element of the list (FIFO
+  // order). NotifyAll, signals all the elements of the list.
   CRITICAL_SECTION waiters_cs_;
-  intptr_t waiters_;
+  MonitorWaitData* waiters_head_;
+  MonitorWaitData* waiters_tail_;
 
   friend class Monitor;