Subscriber which is created with dedicated callback group at runtime not working

[gezp]

Bug report

Required Info:

• Operating System:
  • Ubuntu22.04
• Installation type:
  • Rolling binaries
• Version or commit hash:
  • Rolling
• DDS implementation:
  • default
• Client library (if applicable):
  • rclcpp

Steps to reproduce issue

i create a minimal package to reproduce this issue, see more detail here :https://github.com/gezp/ros2_test_subscriber

ros2 launch ros2_test_subscriber test_subscriber.launch.py use_dedicated_thread:=True

Expected behavior

• subscriber working when activate (in other word, create subscriber),

Actual behavior

• subscriber keeps not working

Additional information

see detailed output here: https://github.com/gezp/ros2_test_subscriber. by the way, it works well under ubuntu20.04 ROS Galactic.

i'm working for nav2, here are some related PRs(navigation2/#2489, navigation2/#3018). navigation2/#2489 worked well when my env was under ubuntu20.04 ROS Rolling, and when i updated my env to ubuntu22.04 ROS Rolling, navigation2/#2489 broke the expected behavior.
CC @SteveMacenski

[fujitatomoya]

@gezp

could you try the following works? (at least my local env fix the problem)

# RMW_IMPLEMENTATION=rmw_cyclonedds_cpp ros2 launch ros2_test_subscriber test_subscriber.launch.py use_dedicated_thread:=True

it works well under ubuntu20.04 ROS Galactic.

this makes sense since default RMW implementation is changed cyclonedds(Galactic/Rolling Ubuntu20.04) to Fast-DDS(Humble/Rolling Ubuntu22.04).

to find out the root cause, we need to dig deeper though.

[gezp]

could you try the following works? (at least my local env fix the problem)

i test locally with cyclonedds under Humble/Rolling Ubuntu22.04, and it also fixes the problem.

[SteveMacenski]

Ah, so its a Fast-DDS specific oddity, that helps!

[fujitatomoya]

according to the following gdb debug, it seems that created subscription is not added to rmw_wait to be executed for Fast-DDS case. So subscription will never be executed by executer.

CC: @MiguelCompany

gdb test_subscriber core

(gdb) info threads
  Id   Target Id                          Frame
* 1    Thread 0x7f380ff15540 (LWP 950397) 0x00007f3810281868 in __GI___clock_nanosleep (clock_id=clock_id@entry=0,
    flags=flags@entry=0, req=0x7ffd1459b1e0, rem=0x7ffd1459b1e0) at ../sysdeps/unix/sysv/linux/clock_nanosleep.c:78
  2    Thread 0x7f380e2d3640 (LWP 950399) __futex_abstimed_wait_common64 (private=<optimized out>, cancel=true,
    abstime=0x0, op=393, expected=0,
    futex_word=0x7f38113d4668 <rclcpp::SignalHandler::get_global_signal_handler()::signal_handler+392>)
    at ./nptl/futex-internal.c:57
  3    Thread 0x7f380dad2640 (LWP 950400) __futex_abstimed_wait_common64 (private=254016488, cancel=true,
    abstime=0x7f380dad1410, op=137, expected=0, futex_word=0x555689e39ab0) at ./nptl/futex-internal.c:57
  4    Thread 0x7f380d24a640 (LWP 950401) __futex_abstimed_wait_common64 (private=2142369199, cancel=true,
    abstime=0x7f380d249410, op=137, expected=0, futex_word=0x555689e3b7f8) at ./nptl/futex-internal.c:57
  5    Thread 0x7f380ca49640 (LWP 950402) 0x00007f38102c3934 in __libc_recvfrom (fd=23, buf=0x555689e4d720, len=65500,
    flags=0, addr=..., addrlen=0x7f380ca47e9c) at ../sysdeps/unix/sysv/linux/recvfrom.c:27
  6    Thread 0x7f380c248640 (LWP 950403) 0x00007f38102c3934 in __libc_recvfrom (fd=24, buf=0x555689e5d710, len=65500,
    flags=0, addr=..., addrlen=0x7f380c246e9c) at ../sysdeps/unix/sysv/linux/recvfrom.c:27
  7    Thread 0x7f380ba47640 (LWP 950404) __futex_abstimed_wait_common64 (private=<optimized out>, cancel=true,
    abstime=0x7f380ba45ca0, op=265, expected=0, futex_word=0x7f380e7db110) at ./nptl/futex-internal.c:57
  8    Thread 0x7f380b246640 (LWP 950405) 0x00007f38102c3934 in __libc_recvfrom (fd=26, buf=0x555689e70010, len=65500,
    flags=0, addr=..., addrlen=0x7f380b244e9c) at ../sysdeps/unix/sysv/linux/recvfrom.c:27
  9    Thread 0x7f380aa38640 (LWP 950406) __futex_abstimed_wait_common64 (private=<optimized out>, cancel=true,
    abstime=0x7f380aa36ca0, op=265, expected=0, futex_word=0x7f380aa3e110) at ./nptl/futex-internal.c:57
  10   Thread 0x7f380a157640 (LWP 950407) __futex_abstimed_wait_common64 (private=0, cancel=true, abstime=0x0, op=393,
    expected=0, futex_word=0x555689e837bc) at ./nptl/futex-internal.c:57
  11   Thread 0x7f380992e640 (LWP 950408) __futex_abstimed_wait_common64 (private=0, cancel=true, abstime=0x0, op=393,
    expected=0, futex_word=0x7f37fc000bb8) at ./nptl/futex-internal.c:57
  12   Thread 0x7f3808f94640 (LWP 950409) __futex_abstimed_wait_common64 (private=0, cancel=true, abstime=0x0, op=393,
    expected=0, futex_word=0x55568a1d54a8) at ./nptl/futex-internal.c:57
  13   Thread 0x7f37fbfff640 (LWP 950410) __futex_abstimed_wait_common64 (private=266173822, cancel=true,
    abstime=0x7f37fbffd0a0, op=137, expected=0, futex_word=0x7f37f4001508) at ./nptl/futex-internal.c:57
  14   Thread 0x7f37fb7fe640 (LWP 950411) __futex_abstimed_wait_common64 (private=0, cancel=true, abstime=0x0, op=393,
    expected=0, futex_word=0x7f37ec00150c) at ./nptl/futex-internal.c:57

1st lets check about `TaskServer::subscription_` to confirm if the object is created.

(gdb) frame 3
ros2/rclcpp#3  0x0000555689159441 in main (argc=4, argv=0x7ffd1459b448)
    at /root/ros2_ws/colcon_ws/src/ros2/ros2_test_subscriber/src/test_subscriber.cpp:157
157         std::this_thread::sleep_for(3000ms);

(gdb) print *server->subscription_.get()
$7 = (rclcpp::Subscription<std_msgs::msg::Int32_<std::allocator<void> >, std::allocator<void>, std_msgs::msg::Int32_<std::allocator<void> >, std_msgs::msg::Int32_<std::allocator<void> >, rclcpp::message_memory_strategy::MessageMemoryStrategy<std_msgs::msg::Int32_<std::allocator<void> >, std::allocator<void> > >) {<rclcpp::SubscriptionBase> = {<std::enable_shared_from_this<rclcpp::SubscriptionBase>> = {_M_weak_this = std::weak_ptr<rclcpp::SubscriptionBase> (use count 1, weak count 2) = {
        get() = 0x7f37ec003bf0}},
    _vptr.SubscriptionBase = 0x55568926ed70 <vtable for rclcpp::Subscription<std_msgs::msg::Int32_<std::allocator<void> >, std::allocator<void>, std_msgs::msg::Int32_<std::allocator<void> >, std_msgs::msg::Int32_<std::allocator<void> >, rclcpp::message_memory_strategy::MessageMemoryStrategy<std_msgs::msg::Int32_<std::allocator<void> >, std::allocator<void> > >+16>,
    node_base_ = 0x55568a046380, node_handle_ = std::shared_ptr<rcl_node_s> (use count 24, weak count 8) = {
      get() = 0x55568a0b8300}, subscription_handle_ = warning: RTTI symbol not found for class 'std::_Sp_counted_deleter<rcl_subscription_s*, rclcpp::SubscriptionBase::SubscriptionBase(rclcpp::node_interfaces::NodeBaseInterface*, rosidl_message_type_support_t const&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, rcl_subscription_options_s const&, bool)::{lambda(rcl_subscription_s*)#1}, std::allocator<void>, (__gnu_cxx::_Lock_policy)2>'
warning: RTTI symbol not found for class 'std::_Sp_counted_deleter<rcl_subscription_s*, rclcpp::SubscriptionBase::SubscriptionBase(rclcpp::node_interfaces::NodeBaseInterface*, rosidl_message_type_support_t const&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, rcl_subscription_options_s const&, bool)::{lambda(rcl_subscription_s*)#1}, std::allocator<void>, (__gnu_cxx::_Lock_policy)2>'
std::shared_ptr<rcl_subscription_s> (use count 2, weak count 0) = {
      get() = 0x7f37ec016160}, intra_process_subscription_handle_ = std::shared_ptr<rcl_subscription_s> (empty) = {
      get() = 0x0}, node_logger_ = {
      name_ = std::shared_ptr<const std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >> (use count 1, weak count 0) = {get() = 0x7f37ec017b40}}, event_handlers_ = std::unordered_map with 1 element = {
...<snip>

and check executor threads. 1st, `create_spin_thread(server)` case

(gdb) thread 14
[Switching to thread 14 (Thread 0x7f37fb7fe640 (LWP 950411))]
#0  __futex_abstimed_wait_common64 (private=0, cancel=true, abstime=0x0, op=393, expected=0, futex_word=0x7f37ec00150c)
    at ./nptl/futex-internal.c:57
57      in ./nptl/futex-internal.c

(gdb) bt
#0  __futex_abstimed_wait_common64 (private=0, cancel=true, abstime=0x0, op=393, expected=0, futex_word=0x7f37ec00150c)
    at ./nptl/futex-internal.c:57
ros2/rclcpp#1  __futex_abstimed_wait_common (cancel=true, private=0, abstime=0x0, clockid=0, expected=0, futex_word=0x7f37ec00150c)
    at ./nptl/futex-internal.c:87
ros2/rclcpp#2  __GI___futex_abstimed_wait_cancelable64 (futex_word=futex_word@entry=0x7f37ec00150c, expected=expected@entry=0,
    clockid=clockid@entry=0, abstime=abstime@entry=0x0, private=private@entry=0) at ./nptl/futex-internal.c:139
ros2/rclcpp#3  0x00007f381022fac1 in __pthread_cond_wait_common (abstime=0x0, clockid=0, mutex=0x7f37ec001510, cond=0x7f37ec0014e0)
    at ./nptl/pthread_cond_wait.c:503
ros2/rclcpp#4  ___pthread_cond_wait (cond=0x7f37ec0014e0, mutex=0x7f37ec001510) at ./nptl/pthread_cond_wait.c:627
ros2/rclcpp#5  0x00007f380fe0a2b1 in std::condition_variable::wait<rmw_fastrtps_shared_cpp::__rmw_wait(char const*, rmw_subscriptions_t*, rmw_guard_conditions_t*, rmw_services_t*, rmw_clients_t*, rmw_events_t*, rmw_wait_set_t*, const rmw_time_t*)::<lambda()> >(std::unique_lock<std::mutex> &, struct {...}) (this=0x7f37ec0014e0, __lock=..., __p=...)
    at /usr/include/c++/11/condition_variable:103
ros2/rclcpp#6  0x00007f380fe09d90 in rmw_fastrtps_shared_cpp::__rmw_wait (identifier=0x7f380fed4266 "rmw_fastrtps_cpp",
    subscriptions=0x7f37ec000f18, guard_conditions=0x7f37ec000f30, services=0x7f37ec000f60, clients=0x7f37ec000f48,
    events=0x7f37ec000f78, wait_set=0x7f37ec000e50, wait_timeout=0x0)
    at /root/ros2_ws/colcon_ws/src/ros2/rmw_fastrtps/rmw_fastrtps_shared_cpp/src/rmw_wait.cpp:176
ros2/rclcpp#7  0x00007f380fec83e7 in rmw_wait (subscriptions=0x7f37ec000f18, guard_conditions=0x7f37ec000f30,
    services=0x7f37ec000f60, clients=0x7f37ec000f48, events=0x7f37ec000f78, wait_set=0x7f37ec000e50, wait_timeout=0x0)
    at /root/ros2_ws/colcon_ws/src/ros2/rmw_fastrtps/rmw_fastrtps_cpp/src/rmw_wait.cpp:33
ros2/rclcpp#8  0x00007f381068c60e in rcl_wait (wait_set=0x7f37fb7fd3d8, timeout=-1)
    at /root/ros2_ws/colcon_ws/src/ros2/rcl/rcl/src/rcl/wait.c:600
ros2/rclcpp#9  0x00007f38110490d5 in rclcpp::Executor::wait_for_work (this=0x7f37fb7fd330, timeout=...)
    at /root/ros2_ws/colcon_ws/src/ros2/rclcpp/rclcpp/src/rclcpp/executor.cpp:750
ros2/rclcpp#10 0x00007f3811049dc8 in rclcpp::Executor::get_next_executable (this=0x7f37fb7fd330, any_executable=..., timeout=...)
    at /root/ros2_ws/colcon_ws/src/ros2/rclcpp/rclcpp/src/rclcpp/executor.cpp:906
ros2/rclcpp#11 0x00007f3811058a6a in rclcpp::executors::SingleThreadedExecutor::spin (this=0x7f37fb7fd330)
    at /root/ros2_ws/colcon_ws/src/ros2/rclcpp/rclcpp/src/rclcpp/executors/single_threaded_executor.cpp:36
ros2/rclcpp#12 0x0000555689167361 in create_spin_thread<std::shared_ptr<TaskServer> >(std::shared_ptr<TaskServer>&)::{lambda()#1}::operator()() const (__closure=0x55568a2c6218)
    at /root/ros2_ws/colcon_ws/src/ros2/ros2_test_subscriber/src/test_subscriber.cpp:136
ros2/rclcpp#13 0x00005556891f5fc3 in std::__invoke_impl<void, create_spin_thread<std::shared_ptr<TaskServer> >(std::shared_ptr<TaskServer>&)::{lambda()#1}>(std::__invoke_other, create_spin_thread<std::shared_ptr<TaskServer> >(std::shared_ptr<TaskServer>&)::{lambda()#1}&&) (__f=...) at /usr/include/c++/11/bits/invoke.h:61
ros2/rclcpp#14 0x00005556891f2f27 in std::__invoke<create_spin_thread<std::shared_ptr<TaskServer> >(std::shared_ptr<TaskServer>&)::{lambda()#1}>(std::shared_ptr<TaskServer>&&) (__fn=...) at /usr/include/c++/11/bits/invoke.h:96
ros2/rclcpp#15 0x00005556891ebe1a in std::thread::_Invoker<std::tuple<create_spin_thread<std::shared_ptr<TaskServer> >(std::shared_ptr<TaskServer>&)::{lambda()#1}> >::_M_invoke<0ul>(std::_Index_tuple<0ul>) (this=0x55568a2c6218)
    at /usr/include/c++/11/bits/std_thread.h:253
ros2/rclcpp#16 0x00005556891e8676 in std::thread::_Invoker<std::tuple<create_spin_thread<std::shared_ptr<TaskServer> >(std::shared_ptr<TaskServer>&)::{lambda()#1}> >::operator()() (this=0x55568a2c6218) at /usr/include/c++/11/bits/std_thread.h:260
ros2/rclcpp#17 0x00005556891e2a50 in std::thread::_State_impl<std::thread::_Invoker<std::tuple<create_spin_thread<std::shared_ptr<TaskServer> >(std::shared_ptr<TaskServer>&)::{lambda()#1}> > >::_M_run() (this=0x55568a2c6210)
    at /usr/include/c++/11/bits/std_thread.h:211

(gdb) frame 7
ros2/rclcpp#7  0x00007f380fec83e7 in rmw_wait (subscriptions=0x7f37ec000f18, guard_conditions=0x7f37ec000f30,
    services=0x7f37ec000f60, clients=0x7f37ec000f48, events=0x7f37ec000f78, wait_set=0x7f37ec000e50, wait_timeout=0x0)
    at /root/ros2_ws/colcon_ws/src/ros2/rmw_fastrtps/rmw_fastrtps_cpp/src/rmw_wait.cpp:33
33        return rmw_fastrtps_shared_cpp::__rmw_wait(

(gdb) print *subscriptions
$9 = {subscriber_count = 1, subscribers = 0x7f37ec0018d0}

(gdb) frame 6
ros2/rclcpp#6  0x00007f380fe09d90 in rmw_fastrtps_shared_cpp::__rmw_wait (identifier=0x7f380fed4266 "rmw_fastrtps_cpp",
    subscriptions=0x7f37ec000f18, guard_conditions=0x7f37ec000f30, services=0x7f37ec000f60, clients=0x7f37ec000f48,
    events=0x7f37ec000f78, wait_set=0x7f37ec000e50, wait_timeout=0x0)
    at /root/ros2_ws/colcon_ws/src/ros2/rmw_fastrtps/rmw_fastrtps_shared_cpp/src/rmw_wait.cpp:176
176           conditionVariable->wait(lock, predicate);

(gdb) print *(CustomSubscriberInfo *)subscriptions->subscribers[0]
$10 = (CustomSubscriberInfo) {<CustomEventInfo> = {
    _vptr.CustomEventInfo = 0x7f380fe59288 <vtable for CustomSubscriberInfo+16>}, data_reader_ = 0x55568a1a60b0,
  listener_ = 0x55568a1a3510,
    type_support_ = {<std::shared_ptr<eprosima::fastdds::dds::TopicDataType>> = std::shared_ptr<eprosima::fastdds::dds::TopicDataType> (use count 17, weak count 0) = {get() = 0x55568a067d10},
    _vptr.TypeSupport = 0x7f380fc39a90 <vtable for eprosima::fastdds::dds::TypeSupport+16>},
  type_support_impl_ = 0x7f38090ec000 <rcl_interfaces::msg::typesupport_fastrtps_cpp::_ParameterEvent__callbacks>,
  subscription_gid_ = {implementation_identifier = 0x7f380fed4266 "rmw_fastrtps_cpp",
    data = "\001\017\243+}\200\320P\001\000\000\000\000\000!\004\000\000\000\000\000\000\000"},
  typesupport_identifier_ = 0x7f381061b000 "rosidl_typesupport_fastrtps_cpp",
    loan_manager_ = std::shared_ptr<rmw_fastrtps_shared_cpp::LoanManager> (empty) = {get() = 0x0}, node_ = 0x55568a0ae720,
  common_context_ = 0x555689e39140, dds_participant_ = 0x555689e39970, subscriber_ = 0x555689ee1430,
  topic_name_mangled_ = "rt/parameter_events", topic_ = 0x55568a067698, filtered_topic_ = 0x0, datareader_qos_ = {

this subscription is `parameter_events` subscription... so then another thread.
thread 12 is `TaskServer::executor_thread_`.

(gdb) thread 12
[Switching to thread 12 (Thread 0x7f3808f94640 (LWP 950409))]
#0  __futex_abstimed_wait_common64 (private=0, cancel=true, abstime=0x0, op=393, expected=0, futex_word=0x55568a1d54a8)
    at ./nptl/futex-internal.c:57
57      ./nptl/futex-internal.c: No such file or directory.

(gdb) bt
#0  __futex_abstimed_wait_common64 (private=0, cancel=true, abstime=0x0, op=393, expected=0, futex_word=0x55568a1d54a8)
    at ./nptl/futex-internal.c:57
ros2/rclcpp#1  __futex_abstimed_wait_common (cancel=true, private=0, abstime=0x0, clockid=0, expected=0, futex_word=0x55568a1d54a8)
    at ./nptl/futex-internal.c:87
ros2/rclcpp#2  __GI___futex_abstimed_wait_cancelable64 (futex_word=futex_word@entry=0x55568a1d54a8, expected=expected@entry=0,
    clockid=clockid@entry=0, abstime=abstime@entry=0x0, private=private@entry=0) at ./nptl/futex-internal.c:139
ros2/rclcpp#3  0x00007f381022fac1 in __pthread_cond_wait_common (abstime=0x0, clockid=0, mutex=0x55568a1d54b0, cond=0x55568a1d5480)
    at ./nptl/pthread_cond_wait.c:503
ros2/rclcpp#4  ___pthread_cond_wait (cond=0x55568a1d5480, mutex=0x55568a1d54b0) at ./nptl/pthread_cond_wait.c:627
ros2/rclcpp#5  0x00007f380fe0a2b1 in std::condition_variable::wait<rmw_fastrtps_shared_cpp::__rmw_wait(char const*, rmw_subscriptions_t*, rmw_guard_conditions_t*, rmw_services_t*, rmw_clients_t*, rmw_events_t*, rmw_wait_set_t*, const rmw_time_t*)::<lambda()> >(std::unique_lock<std::mutex> &, struct {...}) (this=0x55568a1d5480, __lock=..., __p=...)
    at /usr/include/c++/11/condition_variable:103
ros2/rclcpp#6  0x00007f380fe09d90 in rmw_fastrtps_shared_cpp::__rmw_wait (identifier=0x7f380fed4266 "rmw_fastrtps_cpp",
    subscriptions=0x55568a1d4eb8, guard_conditions=0x55568a1d4ed0, services=0x55568a1d4f00, clients=0x55568a1d4ee8,
    events=0x55568a1d4f18, wait_set=0x55568a1bd270, wait_timeout=0x0)
    at /root/ros2_ws/colcon_ws/src/ros2/rmw_fastrtps/rmw_fastrtps_shared_cpp/src/rmw_wait.cpp:176
ros2/rclcpp#7  0x00007f380fec83e7 in rmw_wait (subscriptions=0x55568a1d4eb8, guard_conditions=0x55568a1d4ed0,
    services=0x55568a1d4f00, clients=0x55568a1d4ee8, events=0x55568a1d4f18, wait_set=0x55568a1bd270, wait_timeout=0x0)
    at /root/ros2_ws/colcon_ws/src/ros2/rmw_fastrtps/rmw_fastrtps_cpp/src/rmw_wait.cpp:33
ros2/rclcpp#8  0x00007f381068c60e in rcl_wait (wait_set=0x55568a0741e8, timeout=-1)
    at /root/ros2_ws/colcon_ws/src/ros2/rcl/rcl/src/rcl/wait.c:600
ros2/rclcpp#9  0x00007f38110490d5 in rclcpp::Executor::wait_for_work (this=0x55568a074140, timeout=...)
    at /root/ros2_ws/colcon_ws/src/ros2/rclcpp/rclcpp/src/rclcpp/executor.cpp:750
ros2/rclcpp#10 0x00007f3811049dc8 in rclcpp::Executor::get_next_executable (this=0x55568a074140, any_executable=..., timeout=...)
    at /root/ros2_ws/colcon_ws/src/ros2/rclcpp/rclcpp/src/rclcpp/executor.cpp:906
ros2/rclcpp#11 0x00007f3811058a6a in rclcpp::executors::SingleThreadedExecutor::spin (this=0x55568a074140)
    at /root/ros2_ws/colcon_ws/src/ros2/rclcpp/rclcpp/src/rclcpp/executors/single_threaded_executor.cpp:36
ros2/rclcpp#12 0x000055568915ff10 in TaskServer::TaskServer()::{lambda()#2}::operator()() const (__closure=0x55568a1d56e8)
    at /root/ros2_ws/colcon_ws/src/ros2/ros2_test_subscriber/src/test_subscriber.cpp:59
ros2/rclcpp#13 0x00005556891f60d8 in std::__invoke_impl<void, TaskServer::TaskServer()::{lambda()#2}>(std::__invoke_other, TaskServer::TaskServer()::{lambda()#2}&&) (__f=...) at /usr/include/c++/11/bits/invoke.h:61
ros2/rclcpp#14 0x00005556891f3134 in std::__invoke<TaskServer::TaskServer()::{lambda()#2}>(TaskServer::TaskServer()::{lambda()#2}&&)
    (__fn=...) at /usr/include/c++/11/bits/invoke.h:96
ros2/rclcpp#15 0x00005556891ec45e in std::thread::_Invoker<std::tuple<TaskServer::TaskServer()::{lambda()#2}> >::_M_invoke<0ul>(std::_Index_tuple<0ul>) (this=0x55568a1d56e8) at /usr/include/c++/11/bits/std_thread.h:253
ros2/rclcpp#16 0x00005556891e90d2 in std::thread::_Invoker<std::tuple<TaskServer::TaskServer()::{lambda()#2}> >::operator()() (
    this=0x55568a1d56e8) at /usr/include/c++/11/bits/std_thread.h:260
ros2/rclcpp#17 0x00005556891e50ec in std::thread::_State_impl<std::thread::_Invoker<std::tuple<TaskServer::TaskServer()::{lambda()#2}> > >::_M_run() (this=0x55568a1d56e0) at /usr/include/c++/11/bits/std_thread.h:211
ros2/rclcpp#18 0x00007f38104c22c3 in ?? () from /lib/x86_64-linux-gnu/libstdc++.so.6
ros2/rclcpp#19 0x00007f3810230b43 in start_thread (arg=<optimized out>) at ./nptl/pthread_create.c:442
ros2/rclcpp#20 0x00007f38102c2a00 in clone3 () at ../sysdeps/unix/sysv/linux/x86_64/clone3.S:81

(gdb) frame 7
ros2/rclcpp#7  0x00007f380fec83e7 in rmw_wait (subscriptions=0x55568a1d4eb8, guard_conditions=0x55568a1d4ed0,
    services=0x55568a1d4f00, clients=0x55568a1d4ee8, events=0x55568a1d4f18, wait_set=0x55568a1bd270, wait_timeout=0x0)
    at /root/ros2_ws/colcon_ws/src/ros2/rmw_fastrtps/rmw_fastrtps_cpp/src/rmw_wait.cpp:33
33        return rmw_fastrtps_shared_cpp::__rmw_wait(

(gdb) print *subscriptions
$11 = {subscriber_count = 0, subscribers = 0x0}

`rmw_wait` on pretty much empty... this thread waits on nothing until `guard_conditions` is triggered.

[ros-discourse]

This issue has been mentioned on ROS Discourse. There might be relevant details there:

https://discourse.ros.org/t/ros-2-tsc-meeting-minutes-2022-06-16/26093/1

[SteveMacenski]

Should this ticket be transferred to the RWM for Fast-DDS so they know the ball's in their court?

[clalancette]

@EduPonz @MiguelCompany Could you take a look? This problem only seems to be happening with Fast-DDS. Thanks.

[EduPonz]

Yes, we're looking into it already, we'll keep you posted!

[clalancette]

Yes, we're looking into it already, we'll keep you posted!

Thanks, appreciated.