Error when trying to upload TensorRT engine in Python subprocess

My program has two python process.
Main process stream images in batch and subprocess do inference.

Inside subprocess, trying to load TensorRT engine and have error.

The error happened at

with trt.Runtime(TRT_LOGGER) as runtime:

The whole error is

Traceback (most recent call last):
  File "/usr/lib/python3.5/multiprocessing/", line 249, in _bootstrap
  File "/usr/lib/python3.5/multiprocessing/", line 93, in run
    self._target(*self._args, **self._kwargs)
  File "", line 138, in BatchProcessing
    with trt.Runtime(TRT_LOGGER) as runtime:
TypeError: pybind11::init(): factory function returned nullptr

My subprocess code is as follow

def BatchProcessing(self, e, q, batch1_, batch2_):
        images=np.zeros((BATCHSIZE, CHANNEL*HEIGHT*WIDTH), dtype=np.float32)
        if(os.path.exists(ENGINE_DIR)):#check engine path exists
            with open(ENGINE_DIR, 'rb') as f, trt.Runtime(TRT_LOGGER) as runtime:#read engine
                engine = runtime.deserialize_cuda_engine(

            calibration_files = create_calibration_dataset()
            calibration_cache = "saac_calibration.cache"
            # Process 5 images at a time for calibration
            # This batch size can be different from MaxBatchSize (1 in this example)
            batchstream = calibrator.ImageBatchStream(BATCHSIZE, calibration_files, sub_mean_chw)
            int8_calibrator = calibrator.PythonEntropyCalibrator(["image"], batchstream, calibration_cache)

How to solve the error?

I had a similar issue, and solve it by adding a line of code on the main process, before start the subprocesses:

import multiprocessing