kqueue.c

/*  $OpenBSD: kqueue.c,v 1.5 2002/07/10 14:41:31 art Exp $  */

/*
 * Copyright 2000-2002 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

#define _GNU_SOURCE 1

#include <sys/types.h>
#ifdef HAVE_SYS_TIME_H
#include <sys/time.h>
#else
#include <sys/_libevent_time.h>
#endif
#include <sys/queue.h>
#include <sys/event.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <assert.h>
#ifdef HAVE_INTTYPES_H
#include <inttypes.h>
#endif

/* Some platforms apparently define the udata field of struct kevent as
 * intptr_t, whereas others define it as void*.  There doesn't seem to be an
 * easy way to tell them apart via autoconf, so we need to use OS macros. */
#if defined(HAVE_INTTYPES_H) && !defined(__OpenBSD__) && !defined(__FreeBSD__) && !defined(__darwin__) && !defined(__APPLE__)
#define PTR_TO_UDATA(x) ((intptr_t)(x))
#else
#define PTR_TO_UDATA(x) (x)
#endif

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

#define EVLIST_X_KQINKERNEL 0x1000

#define NEVENT      64

struct kqop {
    struct kevent* changes;
    int nchanges;
    struct kevent* events;
    struct event_list evsigevents[NSIG];
    int nevents;
    int kq;
    pid_t pid;
};

static void* kq_init    (struct event_base*);
static int kq_add   (void*, struct event*);
static int kq_del   (void*, struct event*);
static int kq_dispatch  (struct event_base*, void*, struct timeval*);
static int kq_insert    (struct kqop*, struct kevent*);
static void kq_dealloc (struct event_base*, void*);

const struct eventop kqops = {
    "kqueue",
    kq_init,
    kq_add,
    kq_del,
    kq_dispatch,
    kq_dealloc,
    1 /* need reinit */
};

static void*
kq_init(struct event_base* base)
{
    int i, kq;
    struct kqop* kqueueop;

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

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

    /* Initalize the kernel queue */

    if ((kq = kqueue()) == -1) {
        event_warn("kqueue");
        free (kqueueop);
        return (NULL);
    }

    kqueueop->kq = kq;

    kqueueop->pid = getpid();

    /* Initalize fields */
    kqueueop->changes = malloc(NEVENT * sizeof(struct kevent));
    if (kqueueop->changes == NULL) {
        free (kqueueop);
        return (NULL);
    }
    kqueueop->events = malloc(NEVENT * sizeof(struct kevent));
    if (kqueueop->events == NULL) {
        free (kqueueop->changes);
        free (kqueueop);
        return (NULL);
    }
    kqueueop->nevents = NEVENT;

    /* we need to keep track of multiple events per signal */
    for (i = 0; i < NSIG; ++i) {
        TAILQ_INIT(&kqueueop->evsigevents[i]);
    }

    /* Check for Mac OS X kqueue bug. */
    memset(&kqueueop->changes[0], 0, sizeof kqueueop->changes[0]);
    kqueueop->changes[0].ident = -1;
    kqueueop->changes[0].filter = EVFILT_READ;
    kqueueop->changes[0].flags = EV_ADD;
    /*
     * If kqueue works, then kevent will succeed, and it will
     * stick an error in events[0].  If kqueue is broken, then
     * kevent will fail.
     */
    if (kevent(kq,
               kqueueop->changes, 1, kqueueop->events, NEVENT, NULL) != 1 ||
        kqueueop->events[0].ident != -1 ||
        kqueueop->events[0].flags != EV_ERROR) {
        event_warn("%s: detected broken kqueue; not using.", __func__);
        free(kqueueop->changes);
        free(kqueueop->events);
        free(kqueueop);
        close(kq);
        return (NULL);
    }

    return (kqueueop);
}

static int
kq_insert(struct kqop* kqop, struct kevent* kev)
{
    int nevents = kqop->nevents;

    if (kqop->nchanges == nevents) {
        struct kevent* newchange;
        struct kevent* newresult;

        nevents *= 2;

        newchange = realloc(kqop->changes,
                            nevents * sizeof(struct kevent));
        if (newchange == NULL) {
            event_warn("%s: malloc", __func__);
            return (-1);
        }
        kqop->changes = newchange;

        newresult = realloc(kqop->events,
                            nevents * sizeof(struct kevent));

        /*
         * If we fail, we don't have to worry about freeing,
         * the next realloc will pick it up.
         */
        if (newresult == NULL) {
            event_warn("%s: malloc", __func__);
            return (-1);
        }
        kqop->events = newresult;

        kqop->nevents = nevents;
    }

    memcpy(&kqop->changes[kqop->nchanges++], kev, sizeof(struct kevent));

    event_debug(("%s: fd %d %s%s",
                 __func__, (int)kev->ident,
                 kev->filter == EVFILT_READ ? "EVFILT_READ" : "EVFILT_WRITE",
                 kev->flags == EV_DELETE ? " (del)" : ""));

    return (0);
}

static void
kq_sighandler(int sig)
{
    /* Do nothing here */
}

static int
kq_dispatch(struct event_base* base, void* arg, struct timeval* tv)
{
    struct kqop* kqop = arg;
    struct kevent* changes = kqop->changes;
    struct kevent* events = kqop->events;
    struct event* ev;
    struct timespec ts, *ts_p = NULL;
    int i, res;

    if (tv != NULL) {
        TIMEVAL_TO_TIMESPEC(tv, &ts);
        ts_p = &ts;
    }

    res = kevent(kqop->kq, changes, kqop->nchanges,
                 events, kqop->nevents, ts_p);
    kqop->nchanges = 0;
    if (res == -1) {
        if (errno != EINTR) {
            event_warn("kevent");
            return (-1);
        }

        return (0);
    }

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

    for (i = 0; i < res; i++) {
        int which = 0;

        if (events[i].flags & EV_ERROR) {
            /*
             * Error messages that can happen, when a delete fails.
             *   EBADF happens when the file discriptor has been
             *   closed,
             *   ENOENT when the file discriptor was closed and
             *   then reopened.
             *   EINVAL for some reasons not understood; EINVAL
             *   should not be returned ever; but FreeBSD does :-\
             * An error is also indicated when a callback deletes
             * an event we are still processing.  In that case
             * the data field is set to ENOENT.
             */
            if (events[i].data == EBADF ||
                events[i].data == EINVAL ||
                events[i].data == ENOENT)
                continue;
            errno = events[i].data;
            return (-1);
        }

        if (events[i].filter == EVFILT_READ) {
            which |= EV_READ;
        } else if (events[i].filter == EVFILT_WRITE) {
            which |= EV_WRITE;
        } else if (events[i].filter == EVFILT_SIGNAL) {
            which |= EV_SIGNAL;
        }

        if (!which)
            continue;

        if (events[i].filter == EVFILT_SIGNAL) {
            struct event_list* head =
                (struct event_list*)events[i].udata;
            TAILQ_FOREACH(ev, head, ev_signal_next) {
                event_active(ev, which, events[i].data);
            }
        } else {
            ev = (struct event*)events[i].udata;

            if (!(ev->ev_events & EV_PERSIST))
                ev->ev_flags &= ~EVLIST_X_KQINKERNEL;

            event_active(ev, which, 1);
        }
    }

    return (0);
}


static int
kq_add(void* arg, struct event* ev)
{
    struct kqop* kqop = arg;
    struct kevent kev;

    if (ev->ev_events & EV_SIGNAL) {
        int nsignal = EVENT_SIGNAL(ev);

        assert(nsignal >= 0 && nsignal < NSIG);
        if (TAILQ_EMPTY(&kqop->evsigevents[nsignal])) {
            struct timespec timeout = { 0, 0 };

            memset(&kev, 0, sizeof(kev));
            kev.ident = nsignal;
            kev.filter = EVFILT_SIGNAL;
            kev.flags = EV_ADD;
            kev.udata = PTR_TO_UDATA(&kqop->evsigevents[nsignal]);

            /* Be ready for the signal if it is sent any
             * time between now and the next call to
             * kq_dispatch. */
            if (kevent(kqop->kq, &kev, 1, NULL, 0, &timeout) == -1)
                return (-1);

            if (_evsignal_set_handler(ev->ev_base, nsignal,
                                      kq_sighandler) == -1)
                return (-1);
        }

        TAILQ_INSERT_TAIL(&kqop->evsigevents[nsignal], ev,
                          ev_signal_next);
        ev->ev_flags |= EVLIST_X_KQINKERNEL;
        return (0);
    }

    if (ev->ev_events & EV_READ) {
        memset(&kev, 0, sizeof(kev));
        kev.ident = ev->ev_fd;
        kev.filter = EVFILT_READ;
#ifdef NOTE_EOF
        /* Make it behave like select() and poll() */
        kev.fflags = NOTE_EOF;
#endif
        kev.flags = EV_ADD;
        if (!(ev->ev_events & EV_PERSIST))
            kev.flags |= EV_ONESHOT;
        kev.udata = PTR_TO_UDATA(ev);

        if (kq_insert(kqop, &kev) == -1)
            return (-1);

        ev->ev_flags |= EVLIST_X_KQINKERNEL;
    }

    if (ev->ev_events & EV_WRITE) {
        memset(&kev, 0, sizeof(kev));
        kev.ident = ev->ev_fd;
        kev.filter = EVFILT_WRITE;
        kev.flags = EV_ADD;
        if (!(ev->ev_events & EV_PERSIST))
            kev.flags |= EV_ONESHOT;
        kev.udata = PTR_TO_UDATA(ev);

        if (kq_insert(kqop, &kev) == -1)
            return (-1);

        ev->ev_flags |= EVLIST_X_KQINKERNEL;
    }

    return (0);
}

static int
kq_del(void* arg, struct event* ev)
{
    struct kqop* kqop = arg;
    struct kevent kev;

    if (!(ev->ev_flags & EVLIST_X_KQINKERNEL))
        return (0);

    if (ev->ev_events & EV_SIGNAL) {
        int nsignal = EVENT_SIGNAL(ev);
        struct timespec timeout = { 0, 0 };

        assert(nsignal >= 0 && nsignal < NSIG);
        TAILQ_REMOVE(&kqop->evsigevents[nsignal], ev, ev_signal_next);
        if (TAILQ_EMPTY(&kqop->evsigevents[nsignal])) {
            memset(&kev, 0, sizeof(kev));
            kev.ident = nsignal;
            kev.filter = EVFILT_SIGNAL;
            kev.flags = EV_DELETE;

            /* Because we insert signal events
             * immediately, we need to delete them
             * immediately, too */
            if (kevent(kqop->kq, &kev, 1, NULL, 0, &timeout) == -1)
                return (-1);

            if (_evsignal_restore_handler(ev->ev_base,
                                          nsignal) == -1)
                return (-1);
        }

        ev->ev_flags &= ~EVLIST_X_KQINKERNEL;
        return (0);
    }

    if (ev->ev_events & EV_READ) {
        memset(&kev, 0, sizeof(kev));
        kev.ident = ev->ev_fd;
        kev.filter = EVFILT_READ;
        kev.flags = EV_DELETE;

        if (kq_insert(kqop, &kev) == -1)
            return (-1);

        ev->ev_flags &= ~EVLIST_X_KQINKERNEL;
    }

    if (ev->ev_events & EV_WRITE) {
        memset(&kev, 0, sizeof(kev));
        kev.ident = ev->ev_fd;
        kev.filter = EVFILT_WRITE;
        kev.flags = EV_DELETE;

        if (kq_insert(kqop, &kev) == -1)
            return (-1);

        ev->ev_flags &= ~EVLIST_X_KQINKERNEL;
    }

    return (0);
}

static void
kq_dealloc(struct event_base* base, void* arg)
{
    struct kqop* kqop = arg;

    evsignal_dealloc(base);

    if (kqop->changes)
        free(kqop->changes);
    if (kqop->events)
        free(kqop->events);
    if (kqop->kq >= 0 && kqop->pid == getpid())
        close(kqop->kq);

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