vm: fix race condition in watchdog cleanup

Previous code was calling uv_loop_delete() directly on a running loop,
which led to race condition aborts/segfaults within libuv.  This change
changes the watchdog thread to call uv_run() with UV_RUN_ONCE so that
the call exits after either the timer times out or uv_async_send() is
called from the main thread in Watchdog::Destroy().  The timer/async
handles are then closed and uv_run() with UV_RUN_DEFAULT is called so
that libuv has a chance to cleanup before the thread exits.  The main
thread meanwhile calls uv_thread_join() and then uv_loop_delete() to
complete the cleanup.

1 files changed, 2 insertions, 1 deletions

diff --git a/src/node_watchdog.h b/src/node_watchdog.h
index 1bb4317e33..92a8081047 100644
--- a/src/node_watchdog.h
+++ b/src/node_watchdog.h
@@ -38,12 +38,13 @@ class Watchdog {
   void Destroy();
 
   static void Run(void* arg);
+  static void Async(uv_async_t* async, int status);
   static void Timer(uv_timer_t* timer, int status);
 
   uv_thread_t thread_;
   uv_loop_t* loop_;
+  uv_async_t async_;
   uv_timer_t timer_;
-  bool timer_started_;
   bool thread_created_;
   bool destroyed_;
 };