prepare_callback 3010 src/libsystemd/sd-bus/sd-bus.c                 r = sd_event_source_set_prepare(bus->input_io_event_source, prepare_callback);
prepare_callback  866 src/libsystemd/sd-rtnl/sd-rtnl.c         r = sd_event_source_set_prepare(rtnl->io_event_source, prepare_callback);