Method PopFront

include/Eigen/Eigen/src/ThreadPool/RunQueue.h:70–82

PopFront removes and returns the first element in the queue. If the queue was empty returns default-constructed Work.

  // PopFront removes and returns the first element in the queue.
  // If the queue was empty returns default-constructed Work.
  Work PopFront() {
    unsigned front = front_.load(std::memory_order_relaxed);
    Elem* e = &array_[(front - 1) & 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);
    front = ((front - 1) & kMask2) | (front & ~kMask2);
    front_.store(front, std::memory_order_relaxed);
    return w;
  }

  // PushBack adds w at the end of the queue.
  // If queue is full returns w, otherwise returns default-constructed Work.