commander: only process one vehicle_command/action_request per cycle

- things like arming requests can be dependent on current nav state
that might requested by a previous command, but the state machine
transition will only happen after command processing

src/modules/commander/Commander.cpp

@@ -2710,14 +2710,14 @@ Commander::run()
 		}
 
 		/* handle commands last, as the system needs to be updated to handle them */
-		while (_cmd_sub.updated()) {
+		if (_vehicle_command_sub.updated()) {
 			/* got command */
-			const unsigned last_generation = _cmd_sub.get_last_generation();
+			const unsigned last_generation = _vehicle_command_sub.get_last_generation();
 			vehicle_command_s cmd;
 
-			if (_cmd_sub.copy(&cmd)) {
-				if (_cmd_sub.get_last_generation() != last_generation + 1) {
-					PX4_ERR("vehicle_command lost, generation %u -> %u", last_generation, _cmd_sub.get_last_generation());
+			if (_vehicle_command_sub.copy(&cmd)) {
+				if (_vehicle_command_sub.get_last_generation() != last_generation + 1) {
+					PX4_ERR("vehicle_command lost, generation %u -> %u", last_generation, _vehicle_command_sub.get_last_generation());
 				}
 
 				if (handle_command(cmd)) {
@@ -2726,10 +2726,15 @@ Commander::run()
 			}
 		}
 
-		while (_action_request_sub.updated()) {
+		if (_action_request_sub.updated()) {
+			const unsigned last_generation = _action_request_sub.get_last_generation();
 			action_request_s action_request;
 
 			if (_action_request_sub.copy(&action_request)) {
+				if (_action_request_sub.get_last_generation() != last_generation + 1) {
+					PX4_ERR("action_request lost, generation %u -> %u", last_generation, _action_request_sub.get_last_generation());
+				}
+
 				executeActionRequest(action_request);
 			}
 		}
@@ -3080,8 +3085,11 @@ Commander::run()
 
 		px4_indicate_external_reset_lockout(LockoutComponent::Commander, _armed.armed);
 
+		// sleep if there are no vehicle_commands or action_requests to process
+		if (!_vehicle_command_sub.updated() && !_action_request_sub.updated()) {
 			px4_usleep(COMMANDER_MONITORING_INTERVAL);
 		}
+	}
 
 	rgbled_set_color_and_mode(led_control_s::COLOR_WHITE, led_control_s::MODE_OFF);
 

src/modules/commander/Commander.hpp

@@ -401,7 +401,6 @@ private:
 	// Subscriptions
 	uORB::Subscription					_action_request_sub {ORB_ID(action_request)};
 	uORB::Subscription					_actuator_controls_sub{ORB_ID_VEHICLE_ATTITUDE_CONTROLS};
-	uORB::Subscription					_cmd_sub {ORB_ID(vehicle_command)};
 	uORB::Subscription					_cpuload_sub{ORB_ID(cpuload)};
 	uORB::Subscription					_esc_status_sub{ORB_ID(esc_status)};
 	uORB::Subscription					_estimator_selector_status_sub{ORB_ID(estimator_selector_status)};
@@ -415,6 +414,7 @@ private:
 	uORB::Subscription					_system_power_sub{ORB_ID(system_power)};
 	uORB::Subscription					_vehicle_angular_velocity_sub{ORB_ID(vehicle_angular_velocity)};
 	uORB::Subscription					_vehicle_attitude_sub{ORB_ID(vehicle_attitude)};
+	uORB::Subscription					_vehicle_command_sub{ORB_ID(vehicle_command)};
 	uORB::Subscription					_vehicle_gps_position_sub{ORB_ID(vehicle_gps_position)};
 	uORB::Subscription					_vtol_vehicle_status_sub{ORB_ID(vtol_vehicle_status)};
 	uORB::Subscription					_wind_sub{ORB_ID(wind)};