Asynchronous read hung

[jpswinski]

The following code snippet hung forever:

    datasets = [dataset]
    promise = h5obj.readDatasets(datasets, block=False, enableAttributes=False)
    data = promise[dataset][:]

It got "stuck" in h5promise.py:

  def waitOnResult(self, dataset, timeout=None):
      self.conditions[dataset].acquire()
      if self.datasets[dataset] == None:
          self.conditions[dataset].wait(timeout=timeout)
      self.conditions[dataset].release()
      return self.datasets[dataset] == None

[elidwa]

It is not entirely clear whether the issue was occurring only in multiProcess mode. However, several I/O driver bugs specific to multiProcess were identified and have now been fixed. Additionally, logic was added to h5coro to ensure I/O drivers are properly closed when the h5obj is destroyed. With these changes, the latest code no longer hangs in either multiProcess or the default multithreaded mode.