lambdaofgod opened a new issue #14541: gluon's dataloader crashes if num_workers > 0 URL: https://github.com/apache/incubator-mxnet/issues/14541 ## Description gluon's dataloader sometimes crashes if num_workers > 0 This seems related to #11908 ## Environment info (Required) ``` ----------Python Info---------- Version : 3.6.5 Compiler : GCC 7.2.0 Build : ('default', 'Apr 29 2018 16:14:56') Arch : ('64bit', '') ------------Pip Info----------- Version : 10.0.1 Directory : /home/ubuntu/anaconda3/envs/mxnet_p36/lib/python3.6/site-packages/pip ----------MXNet Info----------- Version : 1.3.1 Directory : /home/ubuntu/anaconda3/envs/mxnet_p36/lib/python3.6/site-packages/mxnet Commit Hash : 19c501680183237d52a862e6ae1dc4ddc296305b ----------System Info---------- Platform : Linux-4.4.0-1077-aws-x86_64-with-debian-stretch-sid system : Linux node : ip-172-31-88-88 release : 4.4.0-1077-aws version : #87-Ubuntu SMP Wed Mar 6 00:03:05 UTC 2019 ----------Hardware Info---------- machine : x86_64 processor : x86_64 Architecture: x86_64 CPU op-mode(s): 32-bit, 64-bit Byte Order: Little Endian CPU(s): 8 On-line CPU(s) list: 0-7 Thread(s) per core: 2 Core(s) per socket: 4 Socket(s): 1 NUMA node(s): 1 Vendor ID: GenuineIntel CPU family: 6 Model: 79 Model name: Intel(R) Xeon(R) CPU E5-2686 v4 @ 2.30GHz Stepping: 1 CPU MHz: 2713.371 CPU max MHz: 3000.0000 CPU min MHz: 1200.0000 BogoMIPS: 4600.11 Hypervisor vendor: Xen Virtualization type: full L1d cache: 32K L1i cache: 32K L2 cache: 256K L3 cache: 46080K NUMA node0 CPU(s): 0-7 Flags: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx pdpe1gb rdtscp lm constant_tsc rep_good nopl xtopology nonstop_tsc aperfmperf pni pclmulqdq ssse3 fma cx16 pcid sse4_1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes xsave avx f16c rdrand hypervisor lahf_lm abm 3dnowprefetch invpcid_single kaiser fsgsbase bmi1 hle avx2 smep bmi2 erms invpcid rtm rdseed adx xsaveopt ----------Network Test---------- Setting timeout: 10 Timing for MXNet: https://github.com/apache/incubator-mxnet, DNS: 0.0011 sec, LOAD: 0.3721 sec. Timing for Gluon Tutorial(en): http://gluon.mxnet.io, DNS: 0.0005 sec, LOAD: 0.0210 sec. Timing for Gluon Tutorial(cn): https://zh.gluon.ai, DNS: 0.0004 sec, LOAD: 0.0163 sec. Timing for FashionMNIST: https://apache-mxnet.s3-accelerate.dualstack.amazonaws.com/gluon/dataset/fashion-mnist/train-labels-idx1-ubyte.gz, DNS: 0.0004 sec, LOAD: 0.1901 sec. Timing for PYPI: https://pypi.python.org/pypi/pip, DNS: 0.0028 sec, LOAD: 0.0553 sec. Timing for Conda: https://repo.continuum.io/pkgs/free/, DNS: 0.0004 sec, LOAD: 0.0240 sec. ``` I'm using MXNet 1.3.1 ## Error Message: Sometimes I get ``` Exception in thread Thread-7: Traceback (most recent call last): File "/home/ubuntu/anaconda3/envs/mxnet_p36/lib/python3.6/threading.py", line 916, in _bootstrap_inner self.run() File "/home/ubuntu/anaconda3/envs/mxnet_p36/lib/python3.6/threading.py", line 864, in run self._target(*self._args, **self._kwargs) File "/home/ubuntu/anaconda3/envs/mxnet_p36/lib/python3.6/site-packages/mxnet/gluon/data/dataloader.py", line 190, in fetcher_loop idx, batch = data_queue.get() File "/home/ubuntu/anaconda3/envs/mxnet_p36/lib/python3.6/multiprocessing/queues.py", line 337, in get return _ForkingPickler.loads(res) File "/home/ubuntu/anaconda3/envs/mxnet_p36/lib/python3.6/site-packages/mxnet/gluon/data/dataloader.py", line 57, in rebuild_ndarray fd = fd.detach() File "/home/ubuntu/anaconda3/envs/mxnet_p36/lib/python3.6/multiprocessing/resource_sharer.py", line 57, in detach with _resource_sharer.get_connection(self._id) as conn: File "/home/ubuntu/anaconda3/envs/mxnet_p36/lib/python3.6/multiprocessing/resource_sharer.py", line 87, in get_connection c = Client(address, authkey=process.current_process().authkey) File "/home/ubuntu/anaconda3/envs/mxnet_p36/lib/python3.6/multiprocessing/connection.py", line 493, in Client answer_challenge(c, authkey) File "/home/ubuntu/anaconda3/envs/mxnet_p36/lib/python3.6/multiprocessing/connection.py", line 737, in answer_challenge response = connection.recv_bytes(256) # reject large message File "/home/ubuntu/anaconda3/envs/mxnet_p36/lib/python3.6/multiprocessing/connection.py", line 216, in recv_bytes buf = self._recv_bytes(maxlength) File "/home/ubuntu/anaconda3/envs/mxnet_p36/lib/python3.6/multiprocessing/connection.py", line 407, in _recv_bytes buf = self._recv(4) File "/home/ubuntu/anaconda3/envs/mxnet_p36/lib/python3.6/multiprocessing/connection.py", line 379, in _recv chunk = read(handle, remaining) ConnectionResetError: [Errno 104] Connection reset by peer ``` Sometimes also ``` Exception in thread Thread-4: Traceback (most recent call last): File "/home/ubuntu/anaconda3/envs/mxnet_p36/lib/python3.6/threading.py", line 916, in _bootstrap_inner self.run() File "/home/ubuntu/anaconda3/envs/mxnet_p36/lib/python3.6/threading.py", line 864, in run self._target(*self._args, **self._kwargs) File "/home/ubuntu/anaconda3/envs/mxnet_p36/lib/python3.6/site-packages/mxnet/gluon/data/dataloader.py", line 190, in fetcher_loop idx, batch = data_queue.get() File "/home/ubuntu/anaconda3/envs/mxnet_p36/lib/python3.6/multiprocessing/queues.py", line 337, in get return _ForkingPickler.loads(res) File "/home/ubuntu/anaconda3/envs/mxnet_p36/lib/python3.6/site-packages/mxnet/gluon/data/dataloader.py", line 57, in rebuild_ndarray fd = fd.detach() File "/home/ubuntu/anaconda3/envs/mxnet_p36/lib/python3.6/multiprocessing/resource_sharer.py", line 57, in detach with _resource_sharer.get_connection(self._id) as conn: File "/home/ubuntu/anaconda3/envs/mxnet_p36/lib/python3.6/multiprocessing/resource_sharer.py", line 87, in get_connection c = Client(address, authkey=process.current_process().authkey) File "/home/ubuntu/anaconda3/envs/mxnet_p36/lib/python3.6/multiprocessing/connection.py", line 487, in Client c = SocketClient(address) File "/home/ubuntu/anaconda3/envs/mxnet_p36/lib/python3.6/multiprocessing/connection.py", line 614, in SocketClient s.connect(address) FileNotFoundError: [Errno 2] No such file or directory ``` ## Minimum reproducible example ``` from mxnet import gluon import numpy as np import itertools import mxnet mxnet.__version__ ## 1.3.1 dummy_dataset = gluon.data.ArrayDataset( [(np.array([ 0, 27, 365, 3], dtype=int), np.array([ 2, 0, 12, 27, 11, 0, 3], dtype=int), 4, 7, 0), (np.array([ 0, 27, 365, 3], dtype=int), np.array([ 2, 0, 12, 27, 11, 0, 3], dtype=int), 4, 7, 1)] ) dummy_dataloader = gluon.data.DataLoader(dummy_dataset, batch_size=1, num_workers=1) list(itertools.islice(dummy_dataloader, 0, 1)) ``` ## What have you tried to solve it? I tried setting `pin_memory` argument to True, but the problem persists.
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