FIX: lockfree MPMC queue should not fail to pop/push when queue is no…

…t empty/full

Signed-off-by: Coldwings <coldwings@me.com>

common/lockfree_queue.h

@@ -179,7 +179,7 @@ class LockfreeMPMCRingQueue : public LockfreeRingQueueBase<T, N> {
  using Base::empty;
  using Base::full;
 
- bool push_weak(const T& x) {
+ bool push(const T& x) {
  auto t = tail.load(std::memory_order_acquire);
  for (;;) {
  auto& slot = slots[idx(t)];
@@ -192,15 +192,16 @@ class LockfreeMPMCRingQueue : public LockfreeRingQueueBase<T, N> {
  }
  } else {
  auto const prevTail = t;
+ auto h = head.load(std::memory_order_acquire);
  t = tail.load(std::memory_order_acquire);
- if (t == prevTail) {
+ if (t == prevTail && Base::check_full(h, t)) {
  return false;
  }
  }
  }
  }
 
- bool pop_weak(T& x) {
+ bool pop(T& x) {
  auto h = head.load(std::memory_order_acquire);
  for (;;) {
  auto& slot = slots[idx(h)];
@@ -213,28 +214,15 @@ class LockfreeMPMCRingQueue : public LockfreeRingQueueBase<T, N> {
  }
  } else {
  auto const prevHead = h;
+ auto t = tail.load(std::memory_order_acquire);
  h = head.load(std::memory_order_acquire);
- if (h == prevHead) {
+ if (h == prevHead && Base::check_empty(h, t)) {
  return false;
  }
  }
  }
  }
 
- bool push(const T& x) {
- do {
- if (push_weak(x)) return true;
- } while (!full());
- return false;
- }
-
- bool pop(T& x) {
- do {
- if (pop_weak(x)) return true;
- } while (!empty());
- return false;
- }
-
  template <typename Pause = ThreadPause>
  void send(const T& x) {
  static_assert(std::is_base_of<PauseBase, Pause>::value,
@@ -536,8 +524,8 @@ namespace common {
  * and load balancing.
  * Watch out that `recv` should run in photon environment (because it has to)
  * use photon semaphore to be notified that new item has sended. `send` could
- * running in photon or std::thread environment (needs to set template `Pause` as
- * `ThreadPause`).
+ * running in photon or std::thread environment (needs to set template `Pause`
+ * as `ThreadPause`).
  *
  * @tparam QueueType shoulde be one of LockfreeMPMCRingQueue,
  * LockfreeBatchMPMCRingQueue, or LockfreeSPSCRingQueue, with their own template