I reproduced the same problem as tjoseph.  Stack trace is here:

  
      gist.github.com
  
  
    https://gist.github.com/sam186/75e500452cbf9b863576e2d47c7733e7 31
stacktrace
#0  0x00007ffff76c1827 in futex_abstimed_wait_cancelable (private=0, abstime=0x0, expected=0, 
    futex_word=0x7fff04000c10) at ../sysdeps/unix/sysv/linux/futex-internal.h:205
#1  do_futex_wait (sem=sem@entry=0x7fff04000c10, abstime=0x0) at sem_waitcommon.c:111
#2  0x00007ffff76c18d4 in __new_sem_wait_slow (sem=0x7fff04000c10, abstime=0x0) at sem_waitcommon.c:181
#3  0x00007ffff76c197a in __new_sem_wait (sem=<optimized out>) at sem_wait.c:29
#4  0x00007ffff7a61b33 in PyThread_acquire_lock_timed (lock=0x7fff04000c10, microseconds=-1000000, intr_flag=1)
    at Python/thread_pthread.h:354
#5  0x00007ffff7a68804 in acquire_timed (lock=0x7fff04000c10, timeout=-1000000000) at ./Modules/_threadmodule.c:68
#6  0x00007ffff7a68946 in lock_PyThread_acquire_lock (self=0x7ffff6456418, args=<optimized out>, 
    kwds=<optimized out>) at ./Modules/_threadmodule.c:151
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test.py
from torch import nn
from torch.autograd import Variable
import torch
 
l = nn.Linear(5,5).cuda()
pl = nn.DataParallel(l)
print("Checkpoint 1")
a = Variable(torch.rand(5,5).cuda(), requires_grad=True)
print("Checkpoint 2")
print(pl(a)) # Here it gets stuck
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