多进程服务器中,epoll的创建应该在创建子进程之后

转：http://blog.csdn.net/wei801004/archive/2009/06/13/4264031.aspx

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:

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#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>

using namespace std;

#define MAXLINE 5

#define OPEN_MAX 100

#define LISTENQ 20

#define SERV_PORT 5000

#define INFTIM 1000

typedef struct 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;

}

else if (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);

}

else if(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;

} else if (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);

}

else if(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:

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#!/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.