深入理解IO复用之epoll

/* According to POSIX.1-2001 */#include <sys/select.h>
/* According to earlier standards */#include <sys/time.h>#include <sys/types.h>#include <unistd.h>
int select(int nfds, fd_set *readfds, fd_set *writefds,           fd_set *exceptfds, struct timeval *timeout);void FD_CLR(int fd, fd_set *set);int  FD_ISSET(int fd, fd_set *set);void FD_SET(int fd, fd_set *set);void FD_ZERO(fd_set *set);

Macro: int FD_SETSIZEThe value of this macro is the maximum number of file descriptorsthat a fd_set object can hold information about. On systems with a fixed maximum number, FD_SETSIZE is at least that number. On some systems, including GNU, there is no absolute limit on the number of descriptors open, but this macro still has a constant value which controls the number of bits in an fd_set; if you get a file descriptor with a value as high as FD_SETSIZE, you cannot put that descriptor into an fd_set. 

//用户数据载体typedef union epoll_data {   void    *ptr;   int      fd;   uint32_t u32;   uint64_t u64;} epoll_data_t;//fd装载入内核的载体 struct epoll_event {     uint32_t     events;    /* Epoll events */     epoll_data_t data;      /* User data variable */ }; //三板斧apiint epoll_create(int size); int epoll_ctl(int epfd, int op, int fd, struct epoll_event *event);  int epoll_wait(int epfd, struct epoll_event *events,                 int maxevents, int timeout);

#define MAX_EVENTS 10struct epoll_event ev, events[MAX_EVENTS];int listen_sock, conn_sock, nfds, epollfd;
/* Set up listening socket, 'listen_sock' (socket(),  bind(), listen()) */
epollfd = epoll_create(10);if(epollfd == -1) {   perror("epoll_create");   exit(EXIT_FAILURE);}
ev.events = EPOLLIN;ev.data.fd = listen_sock;if(epoll_ctl(epollfd, EPOLL_CTL_ADD, listen_sock, &ev) == -1) {   perror("epoll_ctl: listen_sock");   exit(EXIT_FAILURE);}
for(;;) {   nfds = epoll_wait(epollfd, events, MAX_EVENTS, -1);   if (nfds == -1) {       perror("epoll_pwait");       exit(EXIT_FAILURE);   }
   for (n = 0; n < nfds; ++n) {       if (events[n].data.fd == listen_sock) {           //主监听socket有新连接           conn_sock = accept(listen_sock,                           (struct sockaddr *) &local, &addrlen);           if (conn_sock == -1) {               perror("accept");               exit(EXIT_FAILURE);           }           setnonblocking(conn_sock);           ev.events = EPOLLIN | EPOLLET;           ev.data.fd = conn_sock;           if (epoll_ctl(epollfd, EPOLL_CTL_ADD, conn_sock,                       &ev) == -1) {               perror("epoll_ctl: conn_sock");               exit(EXIT_FAILURE);           }       } else {           //已建立连接的可读写句柄           do_use_fd(events[n].data.fd);       }   }}

#ifndef  _LINUX_RBTREE_H#define  _LINUX_RBTREE_H#include <linux/kernel.h>#include <linux/stddef.h>#include <linux/rcupdate.h>
struct rb_node {  unsigned long  __rb_parent_color;  struct rb_node *rb_right;  struct rb_node *rb_left;} __attribute__((aligned(sizeof(long))));/* The alignment might seem pointless, but allegedly CRIS needs it */struct rb_root {  struct rb_node *rb_node;};

struct epitem {  struct rb_node  rbn;        struct list_head  rdllink;   struct epitem  *next;        struct epoll_filefd  ffd;    int  nwait;                   struct list_head  pwqlist;    struct eventpoll  *ep;        struct list_head  fllink;     struct epoll_event  event;  }

struct eventpoll {  spin_lock_t       lock;   struct mutex      mtx;    wait_queue_head_t     wq;   wait_queue_head_t   poll_wait;   struct list_head    rdllist;   //就绪链表  struct rb_root      rbr;      //红黑树根节点   struct epitem      *ovflist;}

revents = ep_item_poll(epi, &pt);//获取就绪事件if (revents) {  if (__put_user(revents, &uevent->events) ||  __put_user(epi->event.data, &uevent->data)) {    list_add(&epi->rdllink, head);//处理失败则重新加入链表    ep_pm_stay_awake(epi);    return eventcnt ? eventcnt : -EFAULT;  }  eventcnt++;  uevent++;  if (epi->event.events & EPOLLONESHOT)    epi->event.events &= EP_PRIVATE_BITS;//EPOLLONESHOT标记的处理  else if (!(epi->event.events & EPOLLET)) {    list_add_tail(&epi->rdllink, &ep->rdllist);//LT模式处理    ep_pm_stay_awake(epi);  }}