EPOLL 이나 POLL에서 EVENT 검사할 때..뭐가 정확한건지

#include <stdlib.h>
#include <stdio.h>
 
#include <sys/types.h>
#include <stropts.h>
#include <poll.h>
 
#include <unistd.h>
#include <errno.h>
#include <string.h>
 
#define NORMAL_DATA 1
#define HIPRI_DATA 2
 
int poll_two_normal( int fd1 , int fd2)
{
struct pollfd poll_list[2];
int retval;
 
poll_list[0].fd = fd1;
poll_list[0].events = POLLIN | POLLPRI;
poll_list[1].fd = fd2;
poll_list[1].events = POLLIN | POLLPRI;
 
while(1)
{
retval = poll(poll_list, (unsigned long) 2 , -1 );
 
/* Retval will always be greater than 0 or -1 in this case.
   Since we're doing it while blocking */
 
if(retval < 0)
{
fprintf(stderr,"Error while polling: %s\n",strerror(errno));
return -1;
}
 
if(((poll_list[0].revents&POLLHUP) == POLLHUP) ||
  ((poll_list[0].revents&POLLERR) == POLLERR) ||
  ((poll_list[0].revents&POLLNVAL) == POLLNVAL) ||
  ((poll_list[1].revents&POLLHUP) == POLLHUP) ||
  ((poll_list[1].revents&POLLERR) == POLLERR) ||
  ((poll_list[1].revents&POLLNVAL) == POLLNVAL)) 
return 0;
 
if((poll_list[0].revents&POLLIN) == POLLIN)
handle(poll_list[0].fd,NORMAL_DATA);
 
if((poll_list[0].revents&POLLPRI) == POLLPRI)
handle(poll_list[0].fd,HIPRI_DATA);
 
if((poll_list[1].revents&POLLIN) == POLLIN)
handle(poll_list[1].fd,NORMAL_DATA);
 
if((poll_list[1].revents&POLLPRI) == POLLPRI)
handle(poll_list[1].fd,HIPRI_DATA);
}
}