Their sample code:

struct libevdev *dev = NULL;
 int fd;
 int rc = 1;

 fd = open("/dev/input/event0", O_RDONLY|O_NONBLOCK);
 rc = libevdev_new_from_fd(fd, &dev);
 if (rc < 0) {
         fprintf(stderr, "Failed to init libevdev (%s)\n", strerror(-rc));
         exit(1);
 }
 printf("Input device name: \"%s\"\n", libevdev_get_name(dev));
 printf("Input device ID: bus %#x vendor %#x product %#x\n",
        libevdev_get_id_bustype(dev),
        libevdev_get_id_vendor(dev),
        libevdev_get_id_product(dev));
 if (!libevdev_has_event_type(dev, EV_REL) ||
     !libevdev_has_event_code(dev, EV_KEY, BTN_LEFT)) {
         printf("This device does not look like a mouse\n");
         exit(1);
 }

 do {
         struct input_event ev;
         rc = libevdev_next_event(dev, LIBEVDEV_READ_FLAG_NORMAL, &ev);
         if (rc == 0)
                 printf("Event: %s %s %d\n",
                        libevdev_event_type_get_name(ev.type),
                        libevdev_event_code_get_name(ev.type, ev.code),
                        ev.value);
 } while (rc == 1 || rc == 0 || rc == -EAGAIN);

Is definitely doing the polling in a blocking way. I think this is intended to be run on a separate thread, and you pass the inputs to your main application thread via some other mechanism.

If your using the polling function, you should be able to do it in a single thread, but then you have to periodically check in between doing other work.