clean more APIs

test=develop

paddle/fluid/framework/threadpool.cc

@@ -25,22 +25,14 @@ DEFINE_int32(dist_threadpool_size, 0,
 
 namespace paddle {
 namespace framework {
-std::mutex threadpool_mu;
 std::unique_ptr<ThreadPool> ThreadPool::threadpool_(nullptr);
 std::once_flag ThreadPool::init_flag_;
 
 ThreadPool* ThreadPool::GetInstance() {
-  std::lock_guard<std::mutex> l(threadpool_mu);
   std::call_once(init_flag_, &ThreadPool::Init);
   return threadpool_.get();
 }
 
-void ThreadPool::TestReset() {
-  std::lock_guard<std::mutex> l(threadpool_mu);
-  threadpool_.reset(nullptr);
-  ThreadPool::Init();
-}
-
 void ThreadPool::Init() {
   if (threadpool_.get() == nullptr) {
     // TODO(Yancey1989): specify the max threads number

paddle/fluid/framework/threadpool.h

@@ -55,10 +55,6 @@ class ThreadPool {
   // Returns the singleton of ThreadPool.
   static ThreadPool* GetInstance();
 
-  // delete current thread pool and create a new one.
-  // Only used by test cases to reset the threadpool.
-  static void TestReset();
-
   ~ThreadPool();
 
   // Run pushes a function to the task queue and returns a std::future

paddle/fluid/framework/threadpool_test.cc

@@ -52,6 +52,5 @@ TEST(ThreadPool, ConcurrentRun) {
   for (auto& t : threads) {
     t.join();
   }
-  framework::ThreadPool::TestReset();
   EXPECT_EQ(sum, ((n + 1) * n) / 2);
 }