Method read

kernel/oswrapper/vspace.h:1184–1212

template <typename T>
T SyncVar<T>::read() {
  _lock.lock();
  if (_set) {
    _lock.unlock();
    return _value;
  }
  if (_sem.is_null()) {
    _sem = vnew<Semaphore>();
  }
  // We can't wait inside the lock without deadlocking; but waiting outside
  // could cause a race condition with _sem being freed due to being idle.
  // Thus, we use start_wait() to insert ourselves into the queue, then
  // use wait_signal() outside the lock to complete waiting.
  //
  // Note: start_wait() will not send a signal to self, as _set is
  // false and therefore _sem->value() must be zero.
  _sem->start_wait(0);
  _lock.unlock();
  internals::wait_signal();
  _lock.lock();
  if (_sem->_idle())
    _sem->post();
  else {
    _sem.free();
    _sem = vnull<Semaphore>();
  }
  _lock.unlock();
  return _value;
}

template <typename T>
Result<T> SyncVar<T>::try_read() {