Thread-safe access to PublisherData #278
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Yadunund
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| std::lock_guard<std::mutex> lock(mutex_); | ||
| return gid_; |
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Because this is returning a raw pointer, this is probably not thread-safe.
That said, from what I can tell there is only one caller of this API, from rmw_get_gid_for_publisher. And there, what we are doing is copying the data into an out parameter.
That suggests to me that this function should be something like:
const void PublisherData::copy_gid(rmw_gid_t * gid) const
{
std::lock_guard<std::mutex> lock(mutex_);
memcpy(gid->data, gid_, RMW_GID_STORAGE_SIZE);
}
(and then update the caller down below as needed). That way we are doing the copy under the lock, which should be safe.
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Good idea! Also had to do something similar for copying the GID into the attachment map 4edbee2
Signed-off-by: Yadunund <[email protected]>
Signed-off-by: Yadunund <[email protected]>
clalancette
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Oct 1, 2024
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This PR replaces
class rmw_publisher_data_twithclass PublisherDatawhich provides thread-safe access to publisher functions. An instance ofPublisherDatais created via theNodeDataclass.rmw_publisher->datais now set tormw_node_t. The assumption here is that the node outlives the publisher similar to the assumption that the context outlives the node. From thisrmw_node_traw_ptr, we are able to obtain it'sNodeDataand then lookup thePublisherDatafor the publisher.One nice thing this PR introduces is the mechanism where shutting down or destroying a parent entity, will shutdown the child entities. Eg. If
rclcpp::shutdown()is invoked, it will firstshutdownall thePublisherData, thenNodeData, and finally the context. We also check for shutdown in the destructor. This is helpful when someone callsnode.resetthere by destroying anrclcpp::Node; this will now shutdown all child entities (onlyPublisherDataso far) and then shutdown the node before clearing memory. We also check foris_shutdownbefore creating a publisher, publishing a message, etc. These principles will be extended to other entities in subsequent PRs.