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fix segmentation fault when adding multiple executors simultaneously #1632

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fix segmentation fault when adding multiple executors simultaneously #1632

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eb13e5f
added lock to prevent simultaneous access of on_shutdown_callbacks_ w…
Apr 15, 2021
ce7ded4
added sleep in test before checking result
Apr 28, 2021
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1 change: 1 addition & 0 deletions rclcpp/src/rclcpp/context.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -344,6 +344,7 @@ Context::shutdown(const std::string & reason)
rclcpp::Context::OnShutdownCallback
Context::on_shutdown(OnShutdownCallback callback)
{
std::lock_guard<std::mutex> lock(on_shutdown_callbacks_mutex_);
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probably not only adding mutex here, but also all access to on_shutdown_callbacks_?

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I think this is not possible without changing the API as the reference is returned

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We should deprecate in the future those getters, returning a reference to an internal container isn't great.

I think that the mutex should also be taken here before calling all the callbacks:

  {
    std::lock_guard<std::mutex> lock(on_shutdown_callbacks_mutex_);
    for (const auto & callback : on_shutdown_callbacks_) {
      callback();
    }
  }

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We should deprecate in the future those getters, returning a reference to an internal container isn't great.

In the general case, I don't agree with this, but in this particular case, I agree.

We could return a copy (since they should be trivially copyable) and lock that operation.

Or we could just drop the accessors. I think I added them just because having hidden state like that can bite you later if you need access to it and have to add an API to get it, or work around it by keeping track of them outside this class (duplicating the effort). So I'd lean towards returning a copy and protecting that with the mutex.

on_shutdown_callbacks_.push_back(callback);
return callback;
}
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1 change: 1 addition & 0 deletions rclcpp/test/rclcpp/test_node.cpp
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Expand Up @@ -2556,6 +2556,7 @@ TEST_F(TestNode, get_publishers_subscriptions_info_by_topic) {
};
rclcpp::QoS qos = rclcpp::QoS(qos_initialization, rmw_qos_profile_default);
auto publisher = node->create_publisher<test_msgs::msg::BasicTypes>(topic_name, qos);
std::this_thread::sleep_for(std::chrono::milliseconds(30));
// List should have one item
auto publisher_list = node->get_publishers_info_by_topic(fq_topic_name);
ASSERT_EQ(publisher_list.size(), (size_t)1);
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