Dead lock log

test.py

import mxnet as mx
from mxnet import gluon

dataset = gluon.data.vision.MNIST()
loader = gluon.data.DataLoader(dataset, 34, last_batch='rollover', num_workers=8)

ctx = [mx.gpu(i) for i in range(2)]
for e in range(10):
    for i, batch in enumerate(loader):
        data = gluon.utils.split_and_load(batch[0], ctx_list=ctx)
        label = gluon.utils.split_and_load(batch[1], ctx_list=ctx)
        mx.nd.waitall()
        print('epoch %d, batch %d' % (e, i))

train.log

INFO:root:Epoch[0] Batch[4999]  Speed: 1315.471563 samples/sec  accuracy=0.110930,top_k_accuracy
_5=0.260795
^CTraceback (most recent call last):
Process Process-7:
  File "train_imagenet.py", line 192, in <module>
Process Process-8:
Traceback (most recent call last):
Process Process-1:
Traceback (most recent call last):
Traceback (most recent call last):
  File "/usr/lib/python2.7/multiprocessing/process.py", line 258, in _bootstrap
Process Process-5:
Process Process-2:
  File "/usr/lib/python2.7/multiprocessing/process.py", line 258, in _bootstrap
  File "/usr/lib/python2.7/multiprocessing/process.py", line 258, in _bootstrap
Process Process-6:
Traceback (most recent call last):
Traceback (most recent call last):
Process Process-3:
Process Process-4:
Traceback (most recent call last):
Traceback (most recent call last):
  File "/usr/lib/python2.7/multiprocessing/process.py", line 258, in _bootstrap
  File "/usr/lib/python2.7/multiprocessing/process.py", line 258, in _bootstrap
Traceback (most recent call last):
  File "/usr/lib/python2.7/multiprocessing/process.py", line 258, in _bootstrap
  File "/usr/lib/python2.7/multiprocessing/process.py", line 258, in _bootstrap
  File "/usr/lib/python2.7/multiprocessing/process.py", line 258, in _bootstrap
    self.run()
    self.run()
    self.run()
  File "/usr/lib/python2.7/multiprocessing/process.py", line 114, in run
  File "/usr/lib/python2.7/multiprocessing/process.py", line 114, in run
  File "/usr/lib/python2.7/multiprocessing/process.py", line 114, in run
    self._target(*self._args, **self._kwargs)
    self._target(*self._args, **self._kwargs)
  File "/home/ubuntu/model_zoo/mxnet/python/mxnet/gluon/data/dataloader.py", line 117, in worker_loop
    self._target(*self._args, **self._kwargs)
  File "/home/ubuntu/model_zoo/mxnet/python/mxnet/gluon/data/dataloader.py", line 117, in worker_loop
  File "/home/ubuntu/model_zoo/mxnet/python/mxnet/gluon/data/dataloader.py", line 117, in worker_loop
    self.run()
  File "/usr/lib/python2.7/multiprocessing/process.py", line 114, in run
    self.run()
    self.run()
    self.run()
    self._target(*self._args, **self._kwargs)
    idx, samples = key_queue.get()
    idx, samples = key_queue.get()
  File "/usr/lib/python2.7/multiprocessing/process.py", line 114, in run
  File "/usr/lib/python2.7/multiprocessing/process.py", line 114, in run
  File "/usr/lib/python2.7/multiprocessing/queues.py", line 117, in get
    idx, samples = key_queue.get()
  File "/home/ubuntu/model_zoo/mxnet/python/mxnet/gluon/data/dataloader.py", line 117, in worker_loop
  File "/usr/lib/python2.7/multiprocessing/queues.py", line 115, in get
  File "/usr/lib/python2.7/multiprocessing/process.py", line 114, in run
    self._target(*self._args, **self._kwargs)
    self._target(*self._args, **self._kwargs)
  File "/usr/lib/python2.7/multiprocessing/queues.py", line 115, in get
    File "/home/ubuntu/model_zoo/mxnet/python/mxnet/gluon/data/dataloader.py", line 117, in worker_loop
    self.run()
  File "/home/ubuntu/model_zoo/mxnet/python/mxnet/gluon/data/dataloader.py", line 117, in worker_loop
    self._target(*self._args, **self._kwargs)
  File "/usr/lib/python2.7/multiprocessing/process.py", line 114, in run
  File "/home/ubuntu/model_zoo/mxnet/python/mxnet/gluon/data/dataloader.py", line 117, in worker_loop
    idx, samples = key_queue.get()
    res = self._recv()
  File "/usr/lib/python2.7/multiprocessing/queues.py", line 115, in get
    self._target(*self._args, **self._kwargs)
  File "/home/ubuntu/model_zoo/mxnet/python/mxnet/gluon/data/dataloader.py", line 65, in recv
    self._rlock.acquire()
    self._rlock.acquire()
  File "/home/ubuntu/model_zoo/mxnet/python/mxnet/gluon/data/dataloader.py", line 117, in worker_loop
    buf = self.recv_bytes()
KeyboardInterrupt
KeyboardInterrupt
    idx, samples = key_queue.get()
    idx, samples = key_queue.get()
KeyboardInterrupt
  File "/usr/lib/python2.7/multiprocessing/queues.py", line 115, in get
  File "/usr/lib/python2.7/multiprocessing/queues.py", line 115, in get
    self._rlock.acquire()
    idx, samples = key_queue.get()
  File "/usr/lib/python2.7/multiprocessing/queues.py", line 115, in get
KeyboardInterrupt
    idx, samples = key_queue.get()
  File "/usr/lib/python2.7/multiprocessing/queues.py", line 115, in get
    train(net, train_data, val_data, ctx, args)
  File "train_imagenet.py", line 144, in train
    self._rlock.acquire()
    self._rlock.acquire()
    for i, batch in enumerate(train_data):
  File "/home/ubuntu/model_zoo/mxnet/python/mxnet/gluon/data/dataloader.py", line 227, in __iter__
KeyboardInterrupt
KeyboardInterrupt
    self._rlock.acquire()
    KeyboardInterrupt
idx, batch = data_queue.get()
  File "/usr/lib/python2.7/multiprocessing/queues.py", line 117, in get
    self._rlock.acquire()
    KeyboardInterrupt
res = self._recv()
  File "/home/ubuntu/model_zoo/mxnet/python/mxnet/gluon/data/dataloader.py", line 65, in recv
    buf = self.recv_bytes()
KeyboardInterrupt