Acquiring locks for getInputVertices and getOutputVertices is not consistent

VertexImpl.getInputVertices() acquires read lock however VertexImpl.getOutputVertices() doesn't.

We also faced with deadlock when using Tez from Hive: see container_jstack.txt

0. Both LlapTaskSchedulerService and VertexImpl defines its own ReentrantReadWriteLock instance.
1. Thread "LlapScheduler" acquired write lock on LlapTaskSchedulerService.lock

LlapTaskSchedulerService.java
  protected void schedulePendingTasks() throws InterruptedException {
    Ref<TaskInfo> downgradedTask = new Ref<>(null);
    writeLock.lock();

2. Thread "Dispatcher thread {Central}" acquired write lock on VertexImpl.lock

VertexImpl.java
  public void handle(VertexEvent event) {
...
    try {
      writeLock.lock();

3. Thread "LlapScheduler" tries acquiring read lock on VertexImpl.lock

VertexImpl.java
  @Override
  public Map<Vertex, Edge> getInputVertices() {
    readLock.lock();

but it is waiting because Thread "Dispatcher thread {Central}" holds the write lock on VertexImpl.lock

4. Thread "Dispatcher thread {Central}" try acquire read lock on LlapTaskSchedulerService.lock

LlapTaskSchedulerService.vaja
  @Override
  public Resource getTotalResources() {
...
    readLock.lock();

but it is waiting because Thread "LlapScheduler" holds the write lock on LlapTaskSchedulerService.lock