多进程服务器中,epoll的创建应该在创建子进程之后

看我的测试代码,似乎应该是在创建子进程之后创建epoll的fd,否则程序将会有问题,试将代码中两个CreateWorker函数的调用位置分别调用,一个在创建epoll fd之前,一个在之后,在调用在创建之前的代码会出问题,在我的机器上(linux内核2.6.26)表现的症状就是所有进程的epoll_wait函数返回0, 而客户端似乎被阻塞了:

服务器端:

#include <iostream>
#include <sys/socket.h>
#include <sys/epoll.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdio.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/wait.h>
usingnamespace std;
#define MAXLINE 5
#define OPEN_MAX 100
#define LISTENQ 20
#define SERV_PORT 5000
#define INFTIM 1000
typedefstruct task_t
{
int fd;
char buffer[100];
int n;
}task_t;
int CreateWorker(int nWorker)
{
if (0 < nWorker)
 {
bool bIsChild;
 pid_t nPid;
while (!bIsChild)
 {
if (0 < nWorker)
 {
 nPid = ::fork();
if (nPid > 0)
 {
 bIsChild = false;
 --nWorker;
 }
elseif (0 == nPid)
 {
 bIsChild = true;
 printf("create worker %d success!/n", ::getpid());
 }
else
 {
 printf("fork error: %s/n", ::strerror(errno));
return -1;
 }
 }
else
 {
int nStatus;
if (-1 == ::wait(&nStatus))
 {
 ++nWorker;
 }
 }
 }
 }
return 0;
}
void setnonblocking(int sock)
{
int opts;
 opts=fcntl(sock,F_GETFL);
if(opts<0)
 {
 perror("fcntl(sock,GETFL)");
 exit(1);
 }
 opts = opts|O_NONBLOCK;
if(fcntl(sock,F_SETFL,opts)<0)
 {
 perror("fcntl(sock,SETFL,opts)");
 exit(1);
 }
}
int main()
{
int i, maxi, listenfd, connfd, sockfd,epfd,nfds;
 ssize_t n;
char line[MAXLINE];
 socklen_t clilen;
struct epoll_event ev,events[20];
struct sockaddr_in clientaddr;
struct sockaddr_in serveraddr;
 listenfd = socket(AF_INET, SOCK_STREAM, 0);
 bzero(&serveraddr, sizeof(serveraddr));
 serveraddr.sin_family = AF_INET;
char *local_addr="127.0.0.1";
 inet_aton(local_addr,&(serveraddr.sin_addr));//htons(SERV_PORT);
 serveraddr.sin_port=htons(SERV_PORT);
// 地址重用
int nOptVal = 1;
 socklen_t nOptLen = sizeof(int);
if (-1 == ::setsockopt(listenfd, SOL_SOCKET, SO_REUSEADDR, &nOptVal, nOptLen))
 {
return -1;
 }
 setnonblocking(listenfd);
 bind(listenfd,(sockaddr *)&serveraddr, sizeof(serveraddr));
 listen(listenfd, LISTENQ);

 CreateWorker(5);

//把socket设置为非阻塞方式

//生成用于处理accept的epoll专用的文件描述符
 epfd=epoll_create(256);
//设置与要处理的事件相关的文件描述符
 ev.data.fd=listenfd;
//设置要处理的事件类型
 ev.events=EPOLLIN|EPOLLET;
//ev.events=EPOLLIN;
//注册epoll事件
 epoll_ctl(epfd,EPOLL_CTL_ADD,listenfd,&ev);

//CreateWorker(5);

 maxi = 0;

 task_t task;
 task_t *ptask;
while(true)
 {
//等待epoll事件的发生
 nfds=epoll_wait(epfd,events,20,500);
//处理所发生的所有事件
for(i=0;i<nfds;++i)
 {
if(events[i].data.fd==listenfd)
 {
 connfd = accept(listenfd,NULL, NULL);
if(connfd<0){
 printf("connfd<0, listenfd = %d/n", listenfd);
 printf("error = %s/n", strerror(errno));
 exit(1);
 }
 setnonblocking(connfd);

//设置用于读操作的文件描述符
 memset(&task, 0, sizeof(task));
 task.fd = connfd;
 ev.data.ptr = &task;
//设置用于注册的读操作事件
 ev.events=EPOLLIN|EPOLLET;
//ev.events=EPOLLIN;
//注册ev
 epoll_ctl(epfd,EPOLL_CTL_ADD,connfd,&ev);
 }
elseif(events[i].events&EPOLLIN)
 {
 cout << "EPOLLIN" << endl;
 ptask = (task_t*)events[i].data.ptr;
 sockfd = ptask->fd;

if ( (ptask->n = read(sockfd, ptask->buffer, 100)) < 0) {
if (errno == ECONNRESET) {
 close(sockfd);
 events[i].data.ptr = NULL;
 } else
 std::cout<<"readline error"<<std::endl;
 } elseif (ptask->n == 0) {
 close(sockfd);
 events[i].data.ptr = NULL;
 }
 ptask->buffer[ptask->n] = '/0';
 cout << "read " << ptask->buffer << endl;

//设置用于写操作的文件描述符
 ev.data.ptr = ptask;
//设置用于注测的写操作事件
 ev.events=EPOLLOUT|EPOLLET;

//修改sockfd上要处理的事件为EPOLLOUT
 epoll_ctl(epfd,EPOLL_CTL_MOD,sockfd,&ev);
 }
elseif(events[i].events&EPOLLOUT)
 {
 cout << "EPOLLOUT" << endl;
 ptask = (task_t*)events[i].data.ptr;
 sockfd = ptask->fd;

 write(sockfd, ptask->buffer, ptask->n);

//设置用于读操作的文件描述符
 ev.data.ptr = ptask;

//修改sockfd上要处理的事件为EPOLIN
 epoll_ctl(epfd,EPOLL_CTL_DEL,sockfd,&ev);
 cout << "write " << ptask->buffer;
 memset(ptask, 0, sizeof(*ptask));
 close(sockfd);
 }
 }
 }
return 0;
}

测试客户端:

#!/usr/bin/perl
use strict;
use Socket;
use IO::Handle;
sub echoclient
{
 my $host = "127.0.0.1";
 my $port = 5000;
 my $protocol = getprotobyname("TCP");
 $host = inet_aton($host);
 socket(SOCK, AF_INET, SOCK_STREAM, $protocol) or die "socket() failed: $!";
 my $dest_addr = sockaddr_in($port, $host);
 connect(SOCK, $dest_addr) or die "connect() failed: $!";
 SOCK->autoflush(1);
 my $msg_out = "hello world/n";
 print "out = ", $msg_out;
 print SOCK $msg_out;
 my $msg_in = <SOCK>;
 print "in = ", $msg_in;
 close SOCK;
}
#&echoclient;
#exit(0);
for (my $i = 0; $i < 9999; $i++)
{
 echoclient;
}

lighttpd 也是在创建完子进程后创建的epoll的fd.