Method PopBack

include/Eigen/Eigen/src/ThreadPool/RunQueue.h:102–115

PopBack removes and returns the last elements in the queue.

  // PopBack removes and returns the last elements in the queue.
  Work PopBack() {
    if (Empty()) return Work();
    EIGEN_MUTEX_LOCK lock(mutex_);
    unsigned back = back_.load(std::memory_order_relaxed);
    Elem* e = &array_[back & kMask];
    uint8_t s = e->state.load(std::memory_order_relaxed);
    if (s != kReady ||
        !e->state.compare_exchange_strong(s, kBusy, std::memory_order_acquire))
      return Work();
    Work w = std::move(e->w);
    e->state.store(kEmpty, std::memory_order_release);
    back_.store(back + 1 + (kSize << 1), std::memory_order_relaxed);
    return w;
  }

  // PopBackHalf removes and returns half last elements in the queue.
  // Returns number of elements removed.