Makefile

all:
	gcc timerfd.c -o timerfd

test:
	./timerfd

clean:
	rm -rf timerfd

timerfd.c

/* timerfd.c */

#include <stdio.h>
#include <stdlib.h>
#include <sys/epoll.h>
#include <time.h>
#include <signal.h>
#include <stdint.h>

struct posix_timer {
	int tfd;
	struct itimerspec ts;
	timer_t timer;
};

int efd;
struct epoll_event ev;
 
void do_handle(struct posix_timer *pt)
{
	int tfd = pt->tfd;

	printf("handled! pt %p\n",pt);

	pt->ts.it_value.tv_sec = 1;
	pt->ts.it_value.tv_nsec = 0;
	pt->ts.it_interval.tv_sec = 0;
	pt->ts.it_interval.tv_nsec = 0;

	timerfd_settime( tfd, 0, &pt->ts, NULL );
}

void start_epoll( int fd, void* data )
{
    int ret;
    int buf;
    struct epoll_event ev,events;
	struct posix_timer* pt;
 
	/* init */
    efd = epoll_create(1);
 
    ev.events = EPOLLIN;
    ev.data.ptr = data;
    if( epoll_ctl(efd,EPOLL_CTL_ADD,fd,&ev) == -1 ){
			perror("epoll_ctl");
			exit(1);
	}
 
    while(1){
    	printf("start to epoll wait...\n");
        ret = epoll_wait(efd, &events, 1, -1);
		if( ret < 0 ){
			perror("epoll_wait");
			exit(1);
		}

    	printf("read...\n");
		pt = events.data.ptr;

        /* events is overwritten by epoll_wait, and have ev.data.fd */
        read( pt->tfd, &buf, sizeof(uint64_t) );
        printf("[%s] ret %d buf %d \n",__FUNCTION__,ret,buf);
		do_handle( pt );
    }
	exit(1);
}

main()
{
    int cnt = 0;
	struct posix_timer pt;
 
	pt.tfd = timerfd_create( CLOCK_REALTIME, 0 );
	if ( pt.tfd < 0 ){
		perror("timerfd_create");
		exit(1);
	}

	pt.ts.it_value.tv_sec = 10;
	pt.ts.it_value.tv_nsec = 0;
	pt.ts.it_interval.tv_sec = 0;
	pt.ts.it_interval.tv_nsec = 0;

	// run timer with rel-timer mode.
	if ( timerfd_settime( pt.tfd, 0, &pt.ts, NULL ) ){
		perror("timerfd_settime");
		exit(1);
	}
 
    if ( fork() == 0 ){
        start_epoll( pt.tfd, &pt );
    }
 
    while(1){
		pause();	
    }
 
}