Refactor actor task queues (#1118)

* Refactor add_task_to_actor_queue into queue_actor_task and insert_actor_task_queue

* Refactor actor task queue to share the waiting task queue

* Fix

src/common/task.cc

@@ -214,6 +214,10 @@ ActorID TaskSpec_actor_id(TaskSpec *spec) {
   return from_flatbuf(message->actor_id());
 }
 
+bool TaskSpec_is_actor_task(TaskSpec *spec) {
+  return !ActorID_equal(TaskSpec_actor_id(spec), NIL_ACTOR_ID);
+}
+
 int64_t TaskSpec_actor_counter(TaskSpec *spec) {
   CHECK(spec);
   auto message = flatbuffers::GetRoot<TaskInfo>(spec);
@@ -227,6 +231,19 @@ bool TaskSpec_actor_is_checkpoint_method(TaskSpec *spec) {
   return actor_counter < 0;
 }
 
+bool TaskSpec_arg_is_actor_dummy_object(TaskSpec *spec, int64_t arg_index) {
+  if (TaskSpec_actor_counter(spec) == 0) {
+    /* The first task does not have any dependencies. */
+    return false;
+  } else if (TaskSpec_actor_is_checkpoint_method(spec)) {
+    /* Checkpoint tasks do not have any dependencies. */
+    return false;
+  } else {
+    /* For all other tasks, the last argument is the dummy object. */
+    return arg_index == (TaskSpec_num_args(spec) - 1);
+  }
+}
+
 UniqueID TaskSpec_driver_id(TaskSpec *spec) {
   CHECK(spec);
   auto message = flatbuffers::GetRoot<TaskInfo>(spec);

src/common/task.h

@@ -126,6 +126,14 @@ FunctionID TaskSpec_function(TaskSpec *spec);
  */
 UniqueID TaskSpec_actor_id(TaskSpec *spec);
 
+/**
+ * Return whether this task is for an actor.
+ *
+ * @param spec The task_spec in question.
+ * @return Whether the task is for an actor.
+ */
+bool TaskSpec_is_actor_task(TaskSpec *spec);
+
 /**
  * Return the actor counter of the task. This starts at 0 and increments by 1
  * every time a new task is submitted to run on the actor.
@@ -135,8 +143,24 @@ UniqueID TaskSpec_actor_id(TaskSpec *spec);
  */
 int64_t TaskSpec_actor_counter(TaskSpec *spec);
 
+/**
+ * Return whether the task is a checkpoint method execution.
+ *
+ * @param spec The task_spec in question.
+ * @return Whether the task is a checkpoint method.
+ */
 bool TaskSpec_actor_is_checkpoint_method(TaskSpec *spec);
 
+/**
+ * Return whether the task's argument is a dummy object. Dummy objects are used
+ * to encode an actor's state dependencies in the task graph.
+ *
+ * @param spec The task_spec in question.
+ * @param arg_index The index of the argument in question.
+ * @return Whether the argument at arg_index is a dummy object.
+ */
+bool TaskSpec_arg_is_actor_dummy_object(TaskSpec *spec, int64_t arg_index);
+
 /**
  * Return the driver ID of the task.
  *