Merge pull request #14259 from jacquesqiao/optimize-thread-pool

Optimize thread pool

Author: jacquesqiao

paddle/fluid/framework/threadpool.cc

@@ -57,10 +57,10 @@ ThreadPool::ThreadPool(int num_threads) : running_(true) {
 ThreadPool::~ThreadPool() {
   {
     // notify all threads to stop running
-    std::lock_guard<std::mutex> l(mutex_);
+    std::unique_lock<std::mutex> l(mutex_);
     running_ = false;
-    scheduled_.notify_all();
   }
+  scheduled_.notify_all();
 
   for (auto& t : threads_) {
     t->join();
@@ -70,19 +70,25 @@ ThreadPool::~ThreadPool() {
 
 void ThreadPool::TaskLoop() {
   while (true) {
-    std::unique_lock<std::mutex> lock(mutex_);
+    Task task;
 
-    scheduled_.wait(
-        lock, [this] { return !this->tasks_.empty() || !this->running_; });
+    {
+      std::unique_lock<std::mutex> lock(mutex_);
+      scheduled_.wait(
+          lock, [this] { return !this->tasks_.empty() || !this->running_; });
 
-    if (!running_ || tasks_.empty()) {
-      return;
-    }
+      if (!running_ && tasks_.empty()) {
+        return;
+      }
+
+      if (tasks_.empty()) {
+        PADDLE_THROW("This thread has no task to Run");
+      }
 
-    // pop a task from the task queue
-    auto task = std::move(tasks_.front());
-    tasks_.pop();
-    lock.unlock();
+      // pop a task from the task queue
+      task = std::move(tasks_.front());
+      tasks_.pop();
+    }
 
     // run the task
     task();

paddle/fluid/framework/threadpool.h

@@ -58,7 +58,7 @@ class ThreadPool {
   ~ThreadPool();
 
   // Run pushes a function to the task queue and returns a std::future
-  // object.  To wait for the completion of the task, call
+  // object. To wait for the completion of the task, call
   // std::future::wait().
   template <typename Callback>
   std::future<void> Run(Callback fn) {
@@ -69,7 +69,6 @@ class ThreadPool {
   template <typename Callback>
   std::future<std::unique_ptr<platform::EnforceNotMet>> RunAndGetException(
       Callback fn) {
-    std::unique_lock<std::mutex> lock(mutex_);
     Task task([fn]() -> std::unique_ptr<platform::EnforceNotMet> {
       try {
         fn();
@@ -84,7 +83,13 @@ class ThreadPool {
       return nullptr;
     });
     std::future<std::unique_ptr<platform::EnforceNotMet>> f = task.get_future();
-    tasks_.push(std::move(task));
+    {
+      std::unique_lock<std::mutex> lock(mutex_);
+      if (!running_) {
+        PADDLE_THROW("enqueue on stopped ThreadPool");
+      }
+      tasks_.push(std::move(task));
+    }
     scheduled_.notify_one();
     return f;
   }