devpoll.c

/*
 * Copyright 2000-2004 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 <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/devpoll.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <assert.h>

#include "event.h"
#include "event-internal.h"
#include "evsignal.h"
#include "log.h"

/* due to limitations in the devpoll interface, we need to keep track of
 * all file descriptors outself.
 */
struct evdevpoll {
    struct event* evread;
    struct event* evwrite;
};

struct devpollop {
    struct evdevpoll* fds;
    int nfds;
    struct pollfd* events;
    int nevents;
    int dpfd;
    struct pollfd* changes;
    int nchanges;
};

static void* devpoll_init    (struct event_base*);
static int devpoll_add    (void*, struct event*);
static int devpoll_del    (void*, struct event*);
static int devpoll_dispatch    (struct event_base*, void*, struct timeval*);
static void devpoll_dealloc    (struct event_base*, void*);

const struct eventop devpollops = {
    "devpoll",
    devpoll_init,
    devpoll_add,
    devpoll_del,
    devpoll_dispatch,
    devpoll_dealloc,
    1 /* need reinit */
};

#define NEVENT    32000

static int
devpoll_commit(struct devpollop* devpollop)
{
    /*
     * Due to a bug in Solaris, we have to use pwrite with an offset of 0.
     * Write is limited to 2GB of data, until it will fail.
     */
    if (pwrite(devpollop->dpfd, devpollop->changes,
               sizeof(struct pollfd) * devpollop->nchanges, 0) == -1)
        return (-1);

    devpollop->nchanges = 0;
    return (0);
}

static int
devpoll_queue(struct devpollop* devpollop, int fd, int events)
{
    struct pollfd* pfd;

    if (devpollop->nchanges >= devpollop->nevents) {
        /*
         * Change buffer is full, must commit it to /dev/poll before
         * adding more
         */
        if (devpoll_commit(devpollop) != 0)
            return (-1);
    }

    pfd = &devpollop->changes[devpollop->nchanges++];
    pfd->fd = fd;
    pfd->events = events;
    pfd->revents = 0;

    return (0);
}

static void*
devpoll_init(struct event_base* base)
{
    int dpfd, nfiles = NEVENT;
    struct rlimit rl;
    struct devpollop* devpollop;

    /* Disable devpoll when this environment variable is set */
    if (evutil_getenv("EVENT_NODEVPOLL"))
        return (NULL);

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

    if (getrlimit(RLIMIT_NOFILE, &rl) == 0 &&
        rl.rlim_cur != RLIM_INFINITY)
        nfiles = rl.rlim_cur;

    /* Initialize the kernel queue */
    if ((dpfd = open("/dev/poll", O_RDWR)) == -1) {
        event_warn("open: /dev/poll");
        free(devpollop);
        return (NULL);
    }

    devpollop->dpfd = dpfd;

    /* Initialize fields */
    devpollop->events = calloc(nfiles, sizeof(struct pollfd));
    if (devpollop->events == NULL) {
        free(devpollop);
        close(dpfd);
        return (NULL);
    }
    devpollop->nevents = nfiles;

    devpollop->fds = calloc(nfiles, sizeof(struct evdevpoll));
    if (devpollop->fds == NULL) {
        free(devpollop->events);
        free(devpollop);
        close(dpfd);
        return (NULL);
    }
    devpollop->nfds = nfiles;

    devpollop->changes = calloc(nfiles, sizeof(struct pollfd));
    if (devpollop->changes == NULL) {
        free(devpollop->fds);
        free(devpollop->events);
        free(devpollop);
        close(dpfd);
        return (NULL);
    }

    evsignal_init(base);

    return (devpollop);
}

static int
devpoll_recalc(struct event_base* base, void* arg, int max)
{
    struct devpollop* devpollop = arg;

    if (max >= devpollop->nfds) {
        struct evdevpoll* fds;
        int nfds;

        nfds = devpollop->nfds;
        while (nfds <= max)
            nfds <<= 1;

        fds = realloc(devpollop->fds, nfds * sizeof(struct evdevpoll));
        if (fds == NULL) {
            event_warn("realloc");
            return (-1);
        }
        devpollop->fds = fds;
        memset(fds + devpollop->nfds, 0,
               (nfds - devpollop->nfds) * sizeof(struct evdevpoll));
        devpollop->nfds = nfds;
    }

    return (0);
}

static int
devpoll_dispatch(struct event_base* base, void* arg, struct timeval* tv)
{
    struct devpollop* devpollop = arg;
    struct pollfd* events = devpollop->events;
    struct dvpoll dvp;
    struct evdevpoll* evdp;
    int i, res, timeout = -1;

    if (devpollop->nchanges)
        devpoll_commit(devpollop);

    if (tv != NULL)
        timeout = tv->tv_sec * 1000 + (tv->tv_usec + 999) / 1000;

    dvp.dp_fds = devpollop->events;
    dvp.dp_nfds = devpollop->nevents;
    dvp.dp_timeout = timeout;

    res = ioctl(devpollop->dpfd, DP_POLL, &dvp);

    if (res == -1) {
        if (errno != EINTR) {
            event_warn("ioctl: DP_POLL");
            return (-1);
        }

        evsignal_process(base);
        return (0);
    } else if (base->sig.evsignal_caught) {
        evsignal_process(base);
    }

    event_debug(("%s: devpoll_wait reports %d", __func__, res));

    for (i = 0; i < res; i++) {
        int which = 0;
        int what = events[i].revents;
        struct event* evread = NULL, *evwrite = NULL;

        assert(events[i].fd < devpollop->nfds);
        evdp = &devpollop->fds[events[i].fd];

        if (what & POLLHUP)
            what |= POLLIN | POLLOUT;
        else if (what & POLLERR)
            what |= POLLIN | POLLOUT;

        if (what & POLLIN) {
            evread = evdp->evread;
            which |= EV_READ;
        }

        if (what & POLLOUT) {
            evwrite = evdp->evwrite;
            which |= EV_WRITE;
        }

        if (!which)
            continue;

        if (evread != NULL && !(evread->ev_events & EV_PERSIST))
            event_del(evread);
        if (evwrite != NULL && evwrite != evread &&
            !(evwrite->ev_events & EV_PERSIST))
            event_del(evwrite);

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

    return (0);
}


static int
devpoll_add(void* arg, struct event* ev)
{
    struct devpollop* devpollop = arg;
    struct evdevpoll* evdp;
    int fd, events;

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

    fd = ev->ev_fd;
    if (fd >= devpollop->nfds) {
        /* Extend the file descriptor array as necessary */
        if (devpoll_recalc(ev->ev_base, devpollop, fd) == -1)
            return (-1);
    }
    evdp = &devpollop->fds[fd];

    /*
     * It's not necessary to OR the existing read/write events that we
     * are currently interested in with the new event we are adding.
     * The /dev/poll driver ORs any new events with the existing events
     * that it has cached for the fd.
     */

    events = 0;
    if (ev->ev_events & EV_READ) {
        if (evdp->evread && evdp->evread != ev) {
            /* There is already a different read event registered */
            return (-1);
        }
        events |= POLLIN;
    }

    if (ev->ev_events & EV_WRITE) {
        if (evdp->evwrite && evdp->evwrite != ev) {
            /* There is already a different write event registered */
            return (-1);
        }
        events |= POLLOUT;
    }

    if (devpoll_queue(devpollop, fd, events) != 0)
        return (-1);

    /* Update events responsible */
    if (ev->ev_events & EV_READ)
        evdp->evread = ev;
    if (ev->ev_events & EV_WRITE)
        evdp->evwrite = ev;

    return (0);
}

static int
devpoll_del(void* arg, struct event* ev)
{
    struct devpollop* devpollop = arg;
    struct evdevpoll* evdp;
    int fd, events;
    int needwritedelete = 1, needreaddelete = 1;

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

    fd = ev->ev_fd;
    if (fd >= devpollop->nfds)
        return (0);
    evdp = &devpollop->fds[fd];

    events = 0;
    if (ev->ev_events & EV_READ)
        events |= POLLIN;
    if (ev->ev_events & EV_WRITE)
        events |= POLLOUT;

    /*
     * The only way to remove an fd from the /dev/poll monitored set is
     * to use POLLREMOVE by itself.  This removes ALL events for the fd
     * provided so if we care about two events and are only removing one
     * we must re-add the other event after POLLREMOVE.
     */

    if (devpoll_queue(devpollop, fd, POLLREMOVE) != 0)
        return (-1);

    if ((events & (POLLIN | POLLOUT)) != (POLLIN | POLLOUT)) {
        /*
         * We're not deleting all events, so we must resubmit the
         * event that we are still interested in if one exists.
         */

        if ((events & POLLIN) && evdp->evwrite != NULL) {
            /* Deleting read, still care about write */
            devpoll_queue(devpollop, fd, POLLOUT);
            needwritedelete = 0;
        } else if ((events & POLLOUT) && evdp->evread != NULL) {
            /* Deleting write, still care about read */
            devpoll_queue(devpollop, fd, POLLIN);
            needreaddelete = 0;
        }
    }

    if (needreaddelete)
        evdp->evread = NULL;
    if (needwritedelete)
        evdp->evwrite = NULL;

    return (0);
}

static void
devpoll_dealloc(struct event_base* base, void* arg)
{
    struct devpollop* devpollop = arg;

    evsignal_dealloc(base);
    if (devpollop->fds)
        free(devpollop->fds);
    if (devpollop->events)
        free(devpollop->events);
    if (devpollop->changes)
        free(devpollop->changes);
    if (devpollop->dpfd >= 0)
        close(devpollop->dpfd);

    memset(devpollop, 0, sizeof(struct devpollop));
    free(devpollop);
}