请原谅我的长篇文章。我会发布代码,以便更容易理解我面临的问题。似乎如果将一个发信号的套接字添加到epoll实例,epoll实例上的epoll_wait将不会阻塞。以下示例让我相信这一点:
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <time.h>
#include <sys/epoll.h>
int MAX_EVENT_COUNT = 10;
int main(int argc, char *argv[])
{
int epollfd = epoll_create( MAX_EVENT_COUNT );
if ( epollfd == -1 )
{
printf("\n Error : epoll_create \n");
return 1;
}
epoll_event ev;
memset(&ev,0,sizeof(ev));
ev.events = EPOLLIN | EPOLLET;
int pipefd[2];
if (pipe(pipefd) == -1)
{
perror("pipe");
exit(EXIT_FAILURE);
}
char ch = 'a';
write(pipefd[1], &ch, 1);
if (epoll_ctl( epollfd , EPOLL_CTL_ADD, pipefd[0], &ev ) == -1 )
{
printf("\n Error : epoll add result \n");
return 1;
}
epoll_event rawResult [MAX_EVENT_COUNT];
int32_t res = epoll_wait( epollfd, rawResult, MAX_EVENT_COUNT, -1 );
if(res!=1)
{
printf("\n Epoll problem \n");
}
else
{
printf("\n OK \n");
}
}
但是下面的示例几乎相同,但这次我向epoll添加了一个发信号的套接字,这次是epoll_wait调用阻塞
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <time.h>
#include <sys/epoll.h>
int MAX_EVENT_COUNT = 10;
int main(int argc, char *argv[])
{
int listenfd = 0;
{
struct sockaddr_in serv_addr;
char sendBuff[1025];
listenfd = socket(AF_INET, SOCK_STREAM, 0);
memset(&serv_addr, '0', sizeof(serv_addr));
memset(sendBuff, '0', sizeof(sendBuff));
serv_addr.sin_family = AF_INET;
serv_addr.sin_addr.s_addr = htonl(INADDR_ANY);
serv_addr.sin_port = htons(5000);
bind(listenfd, (struct sockaddr*)&serv_addr, sizeof(serv_addr));
listen(listenfd, 10);
}
int sockfd = 0, n = 0;
char recvBuff[1024];
struct sockaddr_in serv_addr;
memset(recvBuff, '0',sizeof(recvBuff));
if((sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0)
{
printf("\n Error : Could not create socket \n");
return 1;
}
memset(&serv_addr, '0', sizeof(serv_addr));
serv_addr.sin_family = AF_INET;
serv_addr.sin_port = htons(5000);
if(inet_pton(AF_INET, "127.0.0.1", &serv_addr.sin_addr)<=0)
{
printf("\n inet_pton error occured\n");
return 1;
}
if( connect(sockfd, (struct sockaddr *)&serv_addr, sizeof(serv_addr)) < 0)
{
printf("\n Error : Connect Failed \n");
return 1;
}
int connfd = accept(listenfd, (struct sockaddr*)NULL, NULL);
int epollfd = epoll_create( MAX_EVENT_COUNT );
if ( epollfd == -1 )
{
printf("\n Error : epoll_create \n");
return 1;
}
epoll_event ev;
memset(&ev,0,sizeof(ev));
ev.events = EPOLLIN | EPOLLET;
if (epoll_ctl( epollfd , EPOLL_CTL_ADD, sockfd, &ev ) == -1 )
{
printf("\n Error : epoll add result \n");
return 1;
}
epoll_event rawResult [MAX_EVENT_COUNT];
int32_t res = epoll_wait( epollfd, rawResult, MAX_EVENT_COUNT, -1 );
}
答案 0 :(得分:2)
epoll_wait()
将阻止它正在等待的文件描述符没有事件要报告。在您的情况下,我不相信您已达到epoll_wait()
。假设您的程序已经过了connect()
和accept()
,那么您没有在连接上写入任何数据(在sockfd
上),因此epoll_wait()
将不会检测到任何事件在connfd
。
这与您的第一个程序不同,在pipefd[1]
上调用epoll_wait()
之前,您在pipefd[0]
上写了一个数据字节。