epoll.c

/*
 * 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/_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.
 */
struct evepoll {
        struct event *evread;
        struct event *evwrite;
};

struct epollop {
        struct evepoll *fds;
        int nfds;
        struct epoll_event *events;
        int nevents;
        int epfd;
};

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

#define NEVENT  32000

/* 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)

static void *
epoll_init(struct event_base *base)
{
        int epfd, nfiles = NEVENT;
        struct rlimit rl;
        struct epollop *epollop;

        /* Disable epollueue when this environment variable is set */
        if (getenv("EVENT_NOEPOLL"))
                return (NULL);

        if (getrlimit(RLIMIT_NOFILE, &rl) == 0 &&
            rl.rlim_cur != RLIM_INFINITY) {
                /*
                 * Solaris is somewhat retarded - it's important to drop
                 * backwards compatibility when making changes.  So, don't
                 * dare to put rl.rlim_cur here.
                 */
                nfiles = rl.rlim_cur - 1;
        }

        /* Initalize the kernel queue */

        if ((epfd = epoll_create(nfiles)) == -1) {
                if (errno != ENOSYS)
                        event_warn("epoll_create");
                return (NULL);
        }

        FD_CLOSEONEXEC(epfd);

        if (!(epollop = calloc(1, sizeof(struct epollop))))
                return (NULL);

        epollop->epfd = epfd;

        /* Initalize fields */
        epollop->events = malloc(nfiles * sizeof(struct epoll_event));
        if (epollop->events == NULL) {
                free(epollop);
                return (NULL);
        }
        epollop->nevents = nfiles;

        epollop->fds = calloc(nfiles, sizeof(struct evepoll));
        if (epollop->fds == NULL) {
                free(epollop->events);
                free(epollop);
                return (NULL);
        }
        epollop->nfds = nfiles;

        evsignal_init(base);

        return (epollop);
}

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;
                while (nfds <= max)
                        nfds <<= 1;

                fds = realloc(epollop->fds, nfds * sizeof(struct evepoll));
                if (fds == NULL) {
                        event_warn("realloc");
                        return (-1);
                }
                epollop->fds = fds;
                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);
                }

                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++) {
                int what = events[i].events;
                struct event *evread = NULL, *evwrite = NULL;
                int fd = events[i].data.fd;

                if (fd < 0 || fd >= epollop->nfds)
                        continue;
                evep = &epollop->fds[fd];

                if (what & (EPOLLHUP|EPOLLERR)) {
                        evread = evep->evread;
                        evwrite = evep->evwrite;
                } else {
                        if (what & EPOLLIN) {
                                evread = evep->evread;
                        }

                        if (what & EPOLLOUT) {
                                evwrite = evep->evwrite;
                        }
                }

                if (!(evread||evwrite))
                        continue;

                if (evread != NULL)
                        event_active(evread, EV_READ, 1);
                if (evwrite != NULL)
                        event_active(evwrite, EV_WRITE, 1);
        }

        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;

        if (ev->ev_events & EV_SIGNAL)
                return (evsignal_add(ev));

        fd = ev->ev_fd;
        if (fd >= epollop->nfds) {
                /* Extent the file descriptor array as necessary */
                if (epoll_recalc(ev->ev_base, epollop, fd) == -1)
                        return (-1);
        }
        evep = &epollop->fds[fd];
        op = EPOLL_CTL_ADD;
        events = 0;
        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;

        if (ev->ev_events & EV_READ)
                events |= EPOLLIN;
        if (ev->ev_events & EV_WRITE)
                events |= EPOLLOUT;

        if ((events & (EPOLLIN|EPOLLOUT)) != (EPOLLIN|EPOLLOUT)) {
                if ((events & EPOLLIN) && evep->evwrite != NULL) {
                        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);
}

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);
}