uavcan: improve status reporting

[dakejahl]

• removed mutex from print_status() as this blocks the main loop and causes false positives for HW errors.
• check if any ESC or Servo output function is set and only print status if at least one is set

[dagar]

Did you verify absolutely everything is safe without the mutex?

If not entirely sure you could do more granular locking.

[dakejahl]

Did you verify absolutely everything is safe without the mutex?

If not entirely sure you could do more granular locking.

Yeah I checked everything and it looks like all of these just access member variables. The only risk I see is the array of _functions in the mixer module, but you'd really have to try hard to make it fail and even then I'm not sure it would. Initially I tested with granular locking but it just looks bad. If you want I can add it back, basically just calling unlock/lock after each section.

[DronecodeBot]

This pull request has been mentioned on Discussion Forum for PX4, Pixhawk, QGroundControl, MAVSDK, MAVLink. There might be relevant details there:

https://discuss.px4.io/t/px4-sync-q-a-jan-22-2025/43384/3

[dagar]

What about iterating the nodes here? How could that be safe without taking the mutex?

https://github.com/dakejahl/PX4-Autopilot/blob/eca1c76fbf5e67678bd1bebbd42175607b609fcd/src/drivers/uavcan/uavcan_main.cpp#L1142-L1148

[dakejahl]

What about iterating the nodes here? How could that be safe without taking the mutex?

https://github.com/dakejahl/PX4-Autopilot/blob/eca1c76fbf5e67678bd1bebbd42175607b609fcd/src/drivers/uavcan/uavcan_main.cpp#L1142-L1148

It's iterating over a fixed length array, only printing node status if the timestamp is non-zero

    template <typename Operator>
    void forEachNode(Operator op) const
    {
        for (uint8_t i = 1; i <= NodeID::Max; i++)
        {
            const NodeID nid(i);
            UAVCAN_ASSERT(nid.isUnicast());
            const Entry& entry = getEntry(nid);
            if (entry.time_since_last_update_ms100 >= 0)
            {
                op(nid, entry.status);
            }
        }
    }

    Entry& getEntry(NodeID node_id) const
    {
        if (node_id.get() < 1 || node_id.get() > NodeID::Max)
        {
            handleFatalError("NodeStatusMonitor NodeID");
        }
        return entries_[node_id.get() - 1];
    }

mutable Entry entries_[NodeID::Max];