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epoll.c
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epoll.c
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/*
* Copyright 2000-2003 Niels Provos <provos@citi.umich.edu>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include <stdint.h>
#include <sys/types.h>
#include <sys/resource.h>
#ifdef HAVE_SYS_TIME_H
#include <sys/time.h>
#else
#include <sys/_libevent_time.h>
#endif
#include <sys/queue.h>
#include <sys/epoll.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#ifdef HAVE_FCNTL_H
#include <fcntl.h>
#endif
#include "event.h"
#include "event-internal.h"
#include "evsignal.h"
#include "log.h"
/* due to limitations in the epoll interface, we need to keep track of
* all file descriptors outself.
*/
//支持一个fd有两个event的情形
//存储相应的event指针
struct evepoll {
struct event *evread;
struct event *evwrite;
};
struct epollop {
//通过fds[fd]就可以找到相应的控制结构,新fd总是系统中最小空闲fd
struct evepoll *fds;//evepoll数组,数组索引就是fd大小,数组元素就是读写event
int nfds; //fd的个数
struct epoll_event *events;//用于指定事件
int nevents;
int epfd;//epoll_fd
};
static void *epoll_init (struct event_base *);
static int epoll_add (void *, struct event *);
static int epoll_del (void *, struct event *);
static int epoll_dispatch (struct event_base *, void *, struct timeval *);
static void epoll_dealloc (struct event_base *, void *);
const struct eventop epollops = {
"epoll",
epoll_init,
epoll_add,
epoll_del,
epoll_dispatch,
epoll_dealloc,
1 /* need reinit */
};
#ifdef HAVE_SETFD
#define FD_CLOSEONEXEC(x) do { \
if (fcntl(x, F_SETFD, 1) == -1) \
event_warn("fcntl(%d, F_SETFD)", x); \
} while (0)
#else
#define FD_CLOSEONEXEC(x)
#endif
/* On Linux kernels at least up to 2.6.24.4, epoll can't handle timeout
* values bigger than (LONG_MAX - 999ULL)/HZ. HZ in the wild can be
* as big as 1000, and LONG_MAX can be as small as (1<<31)-1, so the
* largest number of msec we can support here is 2147482. Let's
* round that down by 47 seconds.
*/
#define MAX_EPOLL_TIMEOUT_MSEC (35*60*1000)
#define INITIAL_NFILES 32
#define INITIAL_NEVENTS 32
#define MAX_NEVENTS 4096
static void *
epoll_init(struct event_base *base)
{
int epfd;
struct epollop *epollop;
/* Disable epollueue when this environment variable is set */
if (evutil_getenv("EVENT_NOEPOLL"))
return (NULL);
/* Initalize the kernel queue */
if ((epfd = epoll_create(32000)) == -1) {
if (errno != ENOSYS)
event_warn("epoll_create");
return (NULL);
}
//fcntl(epfd,F_SETFD,1)//将1设置给epfd
FD_CLOSEONEXEC(epfd);
if (!(epollop = calloc(1, sizeof(struct epollop))))
return (NULL);
epollop->epfd = epfd;
//将nfd初始值为32大小,nevents同样如此.相应空间也会进行申请
/* Initalize fields */
epollop->events = malloc(INITIAL_NEVENTS * sizeof(struct epoll_event));
if (epollop->events == NULL) {
free(epollop);
return (NULL);
}
epollop->nevents = INITIAL_NEVENTS;
epollop->fds = calloc(INITIAL_NFILES, sizeof(struct evepoll));
if (epollop->fds == NULL) {
free(epollop->events);
free(epollop);
return (NULL);
}
epollop->nfds = INITIAL_NFILES;
//创建socket pair
evsignal_init(base);
return (epollop);
}
//判断fds数组的空间是否足够,不够加倍直到满足要求
static int
epoll_recalc(struct event_base *base, void *arg, int max)
{
struct epollop *epollop = arg;
if (max >= epollop->nfds) {
struct evepoll *fds;
int nfds;
nfds = epollop->nfds;
//增大策略每一次乘以2直到到达要求为止
while (nfds <= max)
nfds <<= 1;
fds = realloc(epollop->fds, nfds * sizeof(struct evepoll));
if (fds == NULL) {
event_warn("realloc");
return (-1);
}
epollop->fds = fds;
//初始化新添加的部分
memset(fds + epollop->nfds, 0,
(nfds - epollop->nfds) * sizeof(struct evepoll));
epollop->nfds = nfds;
}
return (0);
}
static int
epoll_dispatch(struct event_base *base, void *arg, struct timeval *tv)
{
struct epollop *epollop = arg;
struct epoll_event *events = epollop->events;
struct evepoll *evep;
int i, res, timeout = -1;
if (tv != NULL)
timeout = tv->tv_sec * 1000 + (tv->tv_usec + 999) / 1000;
if (timeout > MAX_EPOLL_TIMEOUT_MSEC) {
/* Linux kernels can wait forever if the timeout is too big;
* see comment on MAX_EPOLL_TIMEOUT_MSEC. */
timeout = MAX_EPOLL_TIMEOUT_MSEC;
}
res = epoll_wait(epollop->epfd, events, epollop->nevents, timeout);
if (res == -1) {
if (errno != EINTR) {
event_warn("epoll_wait");
return (-1);
}
//处理信号
evsignal_process(base);
return (0);
} else if (base->sig.evsignal_caught) {
evsignal_process(base);
}
event_debug(("%s: epoll_wait reports %d", __func__, res));
for (i = 0; i < res; i++) {
//epoll事件
int what = events[i].events;
struct event *evread = NULL, *evwrite = NULL;
int fd = events[i].data.fd;
if (fd < 0 || fd >= epollop->nfds)
continue;
//查找到相应的event指针
evep = &epollop->fds[fd];
if (what & (EPOLLHUP|EPOLLERR)) {//存在挂起或错误
evread = evep->evread;
evwrite = evep->evwrite;
} else {
if (what & EPOLLIN) {
evread = evep->evread;
}
if (what & EPOLLOUT) {
evwrite = evep->evwrite;
}
}
if (!(evread||evwrite))
continue;
//向active_list中插入相应的event,设置event中的ev_res,设置ev_ncalls等
if (evread != NULL)
event_active(evread, EV_READ, 1);
if (evwrite != NULL)
event_active(evwrite, EV_WRITE, 1);
}
//若所有的events都触发,扩大op数组中的events数组,
if (res == epollop->nevents && epollop->nevents < MAX_NEVENTS) {
/* We used all of the event space this time. We should
be ready for more events next time. */
int new_nevents = epollop->nevents * 2;
struct epoll_event *new_events;
// realloc不会破坏原来的数据
new_events = realloc(epollop->events,
new_nevents * sizeof(struct epoll_event));
if (new_events) {
epollop->events = new_events;
epollop->nevents = new_nevents;
}
}
return (0);
}
static int
epoll_add(void *arg, struct event *ev)
{
struct epollop *epollop = arg;
struct epoll_event epev = {0, {0}};
struct evepoll *evep;
int fd, op, events;
//signal 的添加部分,直接调用signal添加函数
if (ev->ev_events & EV_SIGNAL)
return (evsignal_add(ev));
fd = ev->ev_fd;
//fd总是系统中空闲的最小fd,判断fds是否够,不够扩大
if (fd >= epollop->nfds) {
/* Extent the file descriptor array as necessary */
if (epoll_recalc(ev->ev_base, epollop, fd) == -1)
return (-1);
}
//fds 和 events数组的索引是一致的都是fd
evep = &epollop->fds[fd];
op = EPOLL_CTL_ADD;
events = 0;
//若相应的fd已经添加了相应的event
//再次添加回覆盖evepoll中的event指针
if (evep->evread != NULL) {
events |= EPOLLIN;
op = EPOLL_CTL_MOD;
}
if (evep->evwrite != NULL) {
events |= EPOLLOUT;
op = EPOLL_CTL_MOD;
}
if (ev->ev_events & EV_READ)
events |= EPOLLIN;
if (ev->ev_events & EV_WRITE)
events |= EPOLLOUT;
epev.data.fd = fd;
epev.events = events;
if (epoll_ctl(epollop->epfd, op, ev->ev_fd, &epev) == -1)
return (-1);
/* Update events responsible */
if (ev->ev_events & EV_READ)
evep->evread = ev;
if (ev->ev_events & EV_WRITE)
evep->evwrite = ev;
return (0);
}
static int
epoll_del(void *arg, struct event *ev)
{
struct epollop *epollop = arg;
struct epoll_event epev = {0, {0}};
struct evepoll *evep;
int fd, events, op;
int needwritedelete = 1, needreaddelete = 1;
if (ev->ev_events & EV_SIGNAL)
return (evsignal_del(ev));
fd = ev->ev_fd;
if (fd >= epollop->nfds)
return (0);
evep = &epollop->fds[fd];
op = EPOLL_CTL_DEL;
events = 0;
//删除相应fd上的相应事件
if (ev->ev_events & EV_READ)
events |= EPOLLIN;
if (ev->ev_events & EV_WRITE)
events |= EPOLLOUT;
if ((events & (EPOLLIN|EPOLLOUT)) != (EPOLLIN|EPOLLOUT)) {
//若fd上不同时存在EPOLLIN 和EPOLLOUT事件时
if ((events & EPOLLIN) && evep->evwrite != NULL) {
//删除read 不删除write
needwritedelete = 0;
events = EPOLLOUT;
op = EPOLL_CTL_MOD;
} else if ((events & EPOLLOUT) && evep->evread != NULL) {
needreaddelete = 0;
events = EPOLLIN;
op = EPOLL_CTL_MOD;
}
}
epev.events = events;
epev.data.fd = fd;
if (needreaddelete)
evep->evread = NULL;
if (needwritedelete)
evep->evwrite = NULL;
if (epoll_ctl(epollop->epfd, op, fd, &epev) == -1)
return (-1);
return (0);
}
//释放epoll使用的资源
static void
epoll_dealloc(struct event_base *base, void *arg)
{
struct epollop *epollop = arg;
evsignal_dealloc(base);
if (epollop->fds)
free(epollop->fds);
if (epollop->events)
free(epollop->events);
if (epollop->epfd >= 0)
close(epollop->epfd);
memset(epollop, 0, sizeof(struct epollop));
free(epollop);
}