eventfd以及epoll原理分析

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#include <stdio.h>
#include <unistd.h>
#include <sys/time.h>
#include <stdint.h>
#include <pthread.h>
#include <sys/eventfd.h>
#include <sys/epoll.h>
int efd = -1;
void *read_thread(void *dummy)
{
int ret = 0;
uint64_t count = 0;
int ep_fd = -1;
struct epoll_event events[10];
if (efd < 0)
{
printf("efd not inited.\n");
goto fail;
}
ep_fd = epoll_create(1024);
if (ep_fd < 0)
{
perror("epoll_create fail: ");
goto fail;
}
{
struct epoll_event read_event;
read_event.events = EPOLLHUP | EPOLLERR | EPOLLIN;
read_event.data.fd = efd;
ret = epoll_ctl(ep_fd, EPOLL_CTL_ADD, efd, &read_event);
if (ret < 0)
{
perror("epoll ctl failed:");
goto fail;
}
}
while (1)
{
ret = epoll_wait(ep_fd, &events[0], 10, 5000);
if (ret > 0)
{
int i = 0;
for (; i < ret; i++)
{
if (events[i].events & EPOLLHUP)
{
printf("epoll eventfd has epoll hup.\n");
goto fail;
}
else if (events[i].events & EPOLLERR)
{
printf("epoll eventfd has epoll error.\n");
goto fail;
}
else if (events[i].events & EPOLLIN)
{
int event_fd = events[i].data.fd;
ret = read(event_fd, &count, sizeof(count));
if (ret < 0)
{
perror("read fail:");
goto fail;
}
else
{
struct timeval tv;
gettimeofday(&tv, NULL);
printf("success read from efd, read %d bytes(%llu) at %lds %ldus\n",
ret, count, tv.tv_sec, tv.tv_usec);
}
}
}
}
else if (ret == 0)
{
/* time out */
printf("epoll wait timed out.\n");
break;
}
else
{
perror("epoll wait error:");
goto fail;
}
}
fail:
if (ep_fd >= 0)
{
close(ep_fd);
ep_fd = -1;
}
return NULL;
}
int main(int argc, char *argv[])
{
pthread_t pid = 0;
uint64_t count = 0;
int ret = 0;
int i = 0;
efd = eventfd(0, 0);
if (efd < 0)
{
perror("eventfd failed.");
goto fail;
}
ret = pthread_create(&pid, NULL, read_thread, NULL);
if (ret < 0)
{
perror("pthread create:");
goto fail;
}
for (i = 0; i < 5; i++)
{
count = 4;
ret = write(efd, &count, sizeof(count));
if (ret < 0)
{
perror("write event fd fail:");
goto fail;
}
else
{
struct timeval tv;
gettimeofday(&tv, NULL);
printf("success write to efd, write %d bytes(%llu) at %lds %ldus\n",
ret, count, tv.tv_sec, tv.tv_usec);
}
sleep(1);
}
fail:
if (0 != pid)
{
pthread_join(pid, NULL);
pid = 0;
}
if (efd >= 0)
{
close(efd);
efd = -1;
}
return ret;
}

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