Prepared the migration to the new non blocking thread pool

unsupported/Eigen/CXX11/Tensor

@@ -51,11 +51,7 @@ typedef unsigned __int64 uint64_t;
 #endif
 
 #ifdef EIGEN_USE_THREADS
-#include <atomic>
-#include <condition_variable>
-#include <deque>
-#include <mutex>
-#include <thread>
+#include "ThreadPool"
 #endif
 
 #ifdef EIGEN_USE_GPU

unsupported/Eigen/CXX11/src/Tensor/TensorDeviceThreadPool.h

@@ -12,145 +12,9 @@
 
 namespace Eigen {
 
-// This defines an interface that ThreadPoolDevice can take to use
-// custom thread pools underneath.
-class ThreadPoolInterface {
- public:
-  virtual void Schedule(std::function<void()> fn) = 0;
-
-  virtual ~ThreadPoolInterface() {}
-};
-
-// The implementation of the ThreadPool type ensures that the Schedule method
-// runs the functions it is provided in FIFO order when the scheduling is done
-// by a single thread.
-// Environment provides a way to create threads and also allows to intercept
-// task submission and execution.
-template <typename Environment>
-class ThreadPoolTempl : public ThreadPoolInterface {
- public:
-  // Construct a pool that contains "num_threads" threads.
-  explicit ThreadPoolTempl(int num_threads, Environment env = Environment())
-      : env_(env), threads_(num_threads), waiters_(num_threads) {
-    for (int i = 0; i < num_threads; i++) {
-      threads_.push_back(env.CreateThread([this]() { WorkerLoop(); }));
-    }
-  }
-
-  // Wait until all scheduled work has finished and then destroy the
-  // set of threads.
-  ~ThreadPoolTempl() {
-    {
-      // Wait for all work to get done.
-      std::unique_lock<std::mutex> l(mu_);
-      while (!pending_.empty()) {
-        empty_.wait(l);
-      }
-      exiting_ = true;
-
-      // Wakeup all waiters.
-      for (auto w : waiters_) {
-        w->ready = true;
-        w->task.f = nullptr;
-        w->cv.notify_one();
-      }
-    }
-
-    // Wait for threads to finish.
-    for (auto t : threads_) {
-      delete t;
-    }
-  }
-
-  // Schedule fn() for execution in the pool of threads. The functions are
-  // executed in the order in which they are scheduled.
-  void Schedule(std::function<void()> fn) {
-    Task t = env_.CreateTask(std::move(fn));
-    std::unique_lock<std::mutex> l(mu_);
-    if (waiters_.empty()) {
-      pending_.push_back(std::move(t));
-    } else {
-      Waiter* w = waiters_.back();
-      waiters_.pop_back();
-      w->ready = true;
-      w->task = std::move(t);
-      w->cv.notify_one();
-    }
-  }
-
- protected:
-  void WorkerLoop() {
-    std::unique_lock<std::mutex> l(mu_);
-    Waiter w;
-    Task t;
-    while (!exiting_) {
-      if (pending_.empty()) {
-        // Wait for work to be assigned to me
-        w.ready = false;
-        waiters_.push_back(&w);
-        while (!w.ready) {
-          w.cv.wait(l);
-        }
-        t = w.task;
-        w.task.f = nullptr;
-      } else {
-        // Pick up pending work
-        t = std::move(pending_.front());
-        pending_.pop_front();
-        if (pending_.empty()) {
-          empty_.notify_all();
-        }
-      }
-      if (t.f) {
-        mu_.unlock();
-        env_.ExecuteTask(t);
-        t.f = nullptr;
-        mu_.lock();
-      }
-    }
-  }
-
- private:
-  typedef typename Environment::Task Task;
-  typedef typename Environment::EnvThread Thread;
-
-  struct Waiter {
-    std::condition_variable cv;
-    Task task;
-    bool ready;
-  };
-
-  Environment env_;
-  std::mutex mu_;
-  MaxSizeVector<Thread*> threads_;  // All threads
-  MaxSizeVector<Waiter*> waiters_;  // Stack of waiting threads.
-  std::deque<Task> pending_;          // Queue of pending work
-  std::condition_variable empty_;          // Signaled on pending_.empty()
-  bool exiting_ = false;
-};
-
-struct StlThreadEnvironment {
-  struct Task {
-    std::function<void()> f;
-  };
-
-  // EnvThread constructor must start the thread,
-  // destructor must join the thread.
-  class EnvThread {
-   public:
-    EnvThread(std::function<void()> f) : thr_(f) {}
-    ~EnvThread() { thr_.join(); }
-
-   private:
-    std::thread thr_;
-  };
-
-  EnvThread* CreateThread(std::function<void()> f) { return new EnvThread(f); }
-  Task CreateTask(std::function<void()> f) { return Task{std::move(f)}; }
-  void ExecuteTask(const Task& t) { t.f(); }
-};
-
-typedef ThreadPoolTempl<StlThreadEnvironment> ThreadPool;
+// Use the SimpleThreadPool by default. We'll switch to the new non blocking
+// thread pool later.
+typedef SimpleThreadPool ThreadPool;
 
 
 // Barrier is an object that allows one or more threads to wait until