libtorch Tensor + std::future bug example

backtrace.txt

$ OMP_NUM_THREADS=1 gdb python3
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Reading symbols from python3...done.
(gdb) run run.py 2
Starting program: /private/home/hnr/.conda/envs/extdev/bin/python3 run.py 2
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
[New Thread 0x7fffa9c32700 (LWP 17667)]
consume(): Future is ready. Should get it quickly now.
consume(): Got future value. All good.
consume(): Future is ready. Should get it quickly now.
consume(): Got future value. All good.
consume(): Future is ready. Should get it quickly now.
consume(): Got future value. All good.
consume(): Future is ready. Should get it quickly now.
consume(): Got future value. All good.
consume(): Future is ready. Should get it quickly now.
consume(): Got future value. All good.
consume(): Future is ready. Should get it quickly now.
consume(): Got future value. All good.
consume(): Future is ready. Should get it quickly now.
consume(): Got future value. All good.
consume(): Future is ready. Should get it quickly now.
consume(): Got future value. All good.
consume(): Future is ready. Should get it quickly now.
^C
Thread 1 "python3" received signal SIGINT, Interrupt.
0x00007ffff7bc39f3 in futex_wait_cancelable (private=<optimized out>, expected=0, futex_word=0x555556c16028)
    at ../sysdeps/unix/sysv/linux/futex-internal.h:88
88      ../sysdeps/unix/sysv/linux/futex-internal.h: No such file or directory.
(gdb) info threads
  Id   Target Id         Frame
* 1    Thread 0x7ffff7fc3740 (LWP 17643) "python3" 0x00007ffff7bc39f3 in futex_wait_cancelable (private=<optimized out>,
    expected=0, futex_word=0x555556c16028) at ../sysdeps/unix/sysv/linux/futex-internal.h:88
  2    Thread 0x7fffa9c32700 (LWP 17667) "python3" 0x00007ffff7bc3449 in futex_wait (private=<optimized out>,
    expected=32767, futex_word=0x555556c1476c) at ../sysdeps/unix/sysv/linux/futex-internal.h:61
(gdb) thread 2
[Switching to thread 2 (Thread 0x7fffa9c32700 (LWP 17667))]
#0  0x00007ffff7bc3449 in futex_wait (private=<optimized out>, expected=32767, futex_word=0x555556c1476c)
    at ../sysdeps/unix/sysv/linux/futex-internal.h:61
61      ../sysdeps/unix/sysv/linux/futex-internal.h: No such file or directory.
(gdb) bt
#0  0x00007ffff7bc3449 in futex_wait (private=<optimized out>, expected=32767, futex_word=0x555556c1476c)
    at ../sysdeps/unix/sysv/linux/futex-internal.h:61
#1  futex_wait_simple (private=<optimized out>, expected=32767, futex_word=0x555556c1476c)
    at ../sysdeps/nptl/futex-internal.h:135
#2  __pthread_cond_destroy (cond=0x555556c14748) at pthread_cond_destroy.c:54
#3  0x00007fffc6938bbc in std::__future_base::_State_baseV2::~_State_baseV2() ()
   from /private/home/hnr/.conda/envs/extdev/lib/python3.7/site-packages/torch/lib/libcaffe2.so
#4  0x00007fffe869ec75 in std::_Sp_counted_base<(__gnu_cxx::_Lock_policy)2>::_M_release() ()
   from /private/home/hnr/.conda/envs/extdev/lib/python3.7/site-packages/torch/lib/libtorch_python.so
#5  0x00007fffa9c41918 in std::__shared_count<(__gnu_cxx::_Lock_policy)2>::~__shared_count (this=<optimized out>,
    __in_chrg=<optimized out>) at /usr/include/c++/7/bits/shared_ptr_base.h:684
#6  std::__shared_ptr<std::__future_base::_State_baseV2, (__gnu_cxx::_Lock_policy)2>::~__shared_ptr (
    this=<optimized out>, __in_chrg=<optimized out>) at /usr/include/c++/7/bits/shared_ptr_base.h:1123
#7  std::__shared_ptr<std::__future_base::_State_baseV2, (__gnu_cxx::_Lock_policy)2>::reset (this=<synthetic pointer>)
    at /usr/include/c++/7/bits/shared_ptr_base.h:1235
#8  std::__basic_future<std::vector<at::Tensor, std::allocator<at::Tensor> > >::_Reset::~_Reset (
    this=<synthetic pointer>, __in_chrg=<optimized out>) at /usr/include/c++/7/future:753
#9  std::future<std::vector<at::Tensor, std::allocator<at::Tensor> > >::get (this=<synthetic pointer>)
    at /usr/include/c++/7/future:795
#10 Runner::consume (this=0x555556c16000) at bug.cc:38
#11 0x00007fffa9c4fc77 in pybind11::cpp_function::cpp_function<void, Runner, , pybind11::name, pybind11::is_method, pybind11::sibling, pybind11::call_guard<pybind11::gil_scoped_release> >(void (Runner::*)(), pybind11::name const&, pybind11::is_method const&, pybind11::sibling const&, pybind11::call_guard<pybind11::gil_scoped_release> const&)::{lambda(Runner*)#1}::operator()(Runner*) const (c=<optimized out>, __closure=<optimized out>)
    at /private/home/hnr/.conda/envs/extdev/lib/python3.7/site-packages/torch/include/pybind11/pybind11.h:74
#12 pybind11::detail::argument_loader<Runner*>::call_impl<void, pybind11::cpp_function::cpp_function<void, Runner, , pybind11::name, pybind11::is_method, pybind11::sibling, pybind11::call_guard<pybind11::gil_scoped_release> >(void (Runner::*)(), pybind11::name const&, pybind11::is_method const&, pybind11::sibling const&, pybind11::call_guard<pybind11::gil_scoped_release> const&)::{lambda(Runner*)#1}&, 0ul, pybind11::gil_scoped_release>(pybind11::cpp_function::cpp_function<void, Runner, , pybind11::name, pybind11::is_method, pybind11::sibling, pybind11::call_guard<pybind11::gil_scoped_release> >(void (Runner::*)(), pybind11::name const&, pybind11::is_method const&, pybind11::sibling const&, pybind11::call_guard<pybind11::gil_scoped_release> const&)::{lambda(Runner*)#1}&, std::integer_sequence<unsigned long, 0ul>, pybind11::gil_scoped_release&&) (
    f=..., this=<optimized out>)
    at /private/home/hnr/.conda/envs/extdev/lib/python3.7/site-packages/torch/include/pybind11/cast.h:1931
#13 pybind11::detail::argument_loader<Runner*>::call<void, pybind11::gil_scoped_release, pybind11::cpp_function::cpp_function<void, Runner, , pybind11::name, pybind11::is_method, pybind11::sibling, pybind11::call_guard<pybind11::gil_scoped_release> >(void (Runner::*)(), pybind11::name const&, pybind11::is_method const&, pybind11::sibling const&, pybind11::call_guard<pybind11::gil_scoped_release> const&)::{lambda(Runner*)#1}&>(pybind11::cpp_function::cpp_function<void, Runner, , pybind11::name, pybind11::is_method, pybind11::sibling, pybind11::call_guard<pybind11::gil_scoped_release> >(void (Runner::*)(), pybind11::name const&, pybind11::is_method const&, pybind11::sibling const&, pybind11::call_guard<pybind11::gil_scoped_release> const&)::{lambda(Runner*)#1}&) && (f=..., this=0x7fffa9c315f0)
    at /private/home/hnr/.conda/envs/extdev/lib/python3.7/site-packages/torch/include/pybind11/cast.h:1913
#14 void pybind11::cpp_function::initialize<pybind11::cpp_function::initialize<void, Runner, , pybind11::name, pybind11::is_method, pybind11::sibling, pybind11::call_guard<pybind11::gil_scoped_release> >(void (Runner::*)(), pybind11::name const&, pybind11::is_method const&, pybind11::sibling const&, pybind11::call_guard<pybind11::gil_scoped_release> const&)::{lambda(Runner*)#1}, void, Runner*, pybind11::name, pybind11::is_method, pybind11::sibling, pybind11::call_guard<pybind11::gil_scop---Type <return> to continue, or q <return> to quit---q
Quit
(gdb)

bug.cc

/*
 *  CXX=c++ python3 setup.py build develop
 *  Then python run.py
 */

#include <chrono>
#include <deque>
#include <future>
#include <memory>
#include <mutex>

#include <torch/extension.h>

class Runner {
 public:
  void consume(int loops = 10) {
    for (int i = 0; i < loops; ++i) {
      std::promise<torch::Tensor> promise;
      std::future<torch::Tensor> future = promise.get_future();
      {
        std::unique_lock<std::mutex> lock(mu_);
        promises_.push_back(std::move(promise));
      }
      can_produce_.notify_one();

      std::future_status status = future.wait_for(std::chrono::seconds(2));
      AT_ASSERTM(status == std::future_status::ready,
                 "Future timeout reached.");

      std::cout << "consume(): Future is ready. Should get it quickly now."
                << std::endl;
      torch::Tensor tensors = future.get();
      std::cout << "consume(): Got future value. All good." << std::endl;
    }
  }

  void produce(torch::Tensor tensor) {
    std::unique_lock<std::mutex> lock(mu_);
    while (promises_.empty()) {
      can_produce_.wait(lock);
    }

    const int batch_size = promises_.size();

    for (int b = 0; b < batch_size; ++b) {
      promises_[b].set_value(tensor.select(0, b));
    }
    promises_.erase(promises_.begin(), promises_.begin() + batch_size);
  }

 private:
  std::condition_variable can_produce_;

  std::mutex mu_;
  std::deque<std::promise<torch::Tensor>> promises_;
};

PYBIND11_MODULE(tensorbug, m) {
  py::class_<Runner>(m, "Runner")
      .def(py::init<>())
      .def("consume", &Runner::consume,
           py::call_guard<py::gil_scoped_release>(), py::arg("loops"))
      .def("produce", &Runner::produce,
           py::call_guard<py::gil_scoped_release>(), py::arg("tensors"));
}

run.py

import sys
import threading

import torch
import tensorbug

batch_size = 1
loops = 10

runner = tensorbug.Runner()

consume_thread = threading.Thread(target=runner.consume,
                                  args=(loops,))
consume_thread.start()

for _ in range(loops):
    runner.produce(torch.zeros(batch_size, 1))

consume_thread.join()

setup.py

# Build with
#   CXX=c++ python3 setup.py build develop

import setuptools
import sys

from torch.utils import cpp_extension

extra_compile_args = []
extra_link_args = []

if sys.platform == 'darwin':
    extra_compile_args += ['-stdlib=libc++', '-mmacosx-version-min=10.12']
    extra_link_args += ['-stdlib=libc++']


tensorbug = cpp_extension.CppExtension(
    name='tensorbug',
    sources=['bug.cc'],
    language='c++',
    extra_compile_args=['-std=c++17'] + extra_compile_args,
    extra_link_args=extra_link_args,
)


setuptools.setup(
    name='tensorbug',
    ext_modules=[tensorbug],
    cmdclass={'build_ext': cpp_extension.BuildExtension})