Method lock_shared

include/tsutil/Bravo.h:251–277

/ Shared locking

  // Shared locking
  //
  void
  lock_shared(Token &token)
  {
    debug_assert(SLOT_SIZE >= DenseThreadId::num_possible_values());

    // Fast path
    if (_mutex.read_bias.load(std::memory_order_acquire)) {
      size_t index  = DenseThreadId::self() % SLOT_SIZE;
      Slot  &slot   = _mutex.readers[index];
      bool   expect = false;
      if (slot.mu.compare_exchange_strong(expect, true, std::memory_order_relaxed)) {
        // recheck
        if (_mutex.read_bias.load(std::memory_order_acquire)) {
          token = index + 1;
          return;
        } else {
          slot.mu.store(false, std::memory_order_relaxed);
        }
      }
    }

    // Slow path
    _mutex.underlying.lock_shared();
    if (_mutex.read_bias.load(std::memory_order_acquire) == false && _now() >= _mutex.inhibit_until) {
      _mutex.read_bias.store(true, std::memory_order_release);
    }
  }

  bool
  try_lock_shared(Token &token)