Linux-Xenomai Serial Communication using xeno_16550A module - interrupt

Question

I'm starter of RTOS and I'm using Xenomai v2.6.3.
I'm trying to get some data using Serial communication.
I did my best on the task following the xenomai's guide and open sources, but it doesn't work well.
the link of the guide --> (https://xenomai.org//serial-16550a-driver/)
I just followed the sequence to use the module xeno_16550A. (with port io = 0x2f8 and irq=3)
I followed open source http://www.acadis.org/pages/captain.at/serial-port-example
It works well in write task, but read task doesn't work well.
It gave me the error sentence with error while RTSER_RTIOC_WAIT_EVENT, code -110 (it means connection timed out)
Moreover I checked the irq number3 by typing command 'cat /proc/xenomai/irq', but the interrupt number doesn't increase.
In my case, I don't need to write data, so I erase the write task code.
The read task proc is follow
void read_task_proc(void *arg) {
int ret;
ssize_t red = 0;
struct rtser_event rx_event;
while (1) {
/* waiting for event */
ret = rt_dev_ioctl(my_fd, RTSER_RTIOC_WAIT_EVENT, &rx_event );
if (ret) {
printf(RTASK_PREFIX "error while RTSER_RTIOC_WAIT_EVENT, code %d\n",ret);
if (ret == -ETIMEDOUT)
continue;
break;
}
unsigned char buf[1];
red = rt_dev_read(my_fd, &buf, 1);
if (red < 0 ) {
printf(RTASK_PREFIX "error while rt_dev_read, code %d\n",red);
} else {
printf(RTASK_PREFIX "only %d byte received , char : %c\n",red,buf[0]);
}
}
exit_read_task:
if (my_state & STATE_FILE_OPENED) {
if (!close_file( my_fd, READ_FILE " (rtser)")) {
my_state &= ~STATE_FILE_OPENED;
}
}
printf(RTASK_PREFIX "exit\n");
}
I could guess the causes of the problem.
buffer size or buffer is already full when new data is received.
rx_interrupt doesn't work....
I want to check whether the two things are wrong or not, but How can I check?
Furthermore, does anybody know the cause of the problem? Please give me comments.