evport.c

/*
 * Submitted by David Pacheco (dp.spambait@gmail.com)
 *
 * 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 SUN MICROSYSTEMS, INC. ``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 SUN MICROSYSTEMS, INC. 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.
 */

/*
 * Copyright (c) 2007 Sun Microsystems. All rights reserved.
 * Use is subject to license terms.
 */

/*
 * evport.c: event backend using Solaris 10 event ports. See port_create(3C).
 * This implementation is loosely modeled after the one used for select(2) (in
 * select.c).
 *
 * The outstanding events are tracked in a data structure called evport_data.
 * Each entry in the ed_fds array corresponds to a file descriptor, and contains
 * pointers to the read and write events that correspond to that fd. (That is,
 * when the file is readable, the "read" event should handle it, etc.)
 *
 * evport_add and evport_del update this data structure. evport_dispatch uses it
 * to determine where to callback when an event occurs (which it gets from
 * port_getn).
 *
 * Helper functions are used: grow() grows the file descriptor array as
 * necessary when large fd's come in. reassociate() takes care of maintaining
 * the proper file-descriptor/event-port associations.
 *
 * As in the select(2) implementation, signals are handled by evsignal.
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include <sys/time.h>
#include <assert.h>
#include <sys/queue.h>
#include <errno.h>
#include <poll.h>
#include <port.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
#ifdef CHECK_INVARIANTS
#include <assert.h>
#endif

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


/*
 * Default value for ed_nevents, which is the maximum file descriptor number we
 * can handle. If an event comes in for a file descriptor F > nevents, we will
 * grow the array of file descriptors, doubling its size.
 */
#define DEFAULT_NFDS    16


/*
 * EVENTS_PER_GETN is the maximum number of events to retrieve from port_getn on
 * any particular call. You can speed things up by increasing this, but it will
 * (obviously) require more memory.
 */
#define EVENTS_PER_GETN 8

/*
 * Per-file-descriptor information about what events we're subscribed to. These
 * fields are NULL if no event is subscribed to either of them.
 */

struct fd_info {
    struct event* fdi_revt; /* the event responsible for the "read"  */
    struct event* fdi_wevt; /* the event responsible for the "write" */
};

#define FDI_HAS_READ(fdi)  ((fdi)->fdi_revt != NULL)
#define FDI_HAS_WRITE(fdi) ((fdi)->fdi_wevt != NULL)
#define FDI_HAS_EVENTS(fdi) (FDI_HAS_READ(fdi) || FDI_HAS_WRITE(fdi))
#define FDI_TO_SYSEVENTS(fdi) (FDI_HAS_READ(fdi) ? POLLIN : 0) | \
    (FDI_HAS_WRITE(fdi) ? POLLOUT : 0)

struct evport_data {
    int         ed_port;    /* event port for system events  */
    int     ed_nevents; /* number of allocated fdi's     */
    struct fd_info* ed_fds;     /* allocated fdi table       */
    /* fdi's that we need to reassoc */
    int ed_pending[EVENTS_PER_GETN]; /* fd's with pending events */
};

static void*    evport_init (struct event_base*);
static int  evport_add  (void*, struct event*);
static int  evport_del  (void*, struct event*);
static int  evport_dispatch (struct event_base*, void*, struct timeval*);
static void evport_dealloc  (struct event_base*, void*);

const struct eventop evportops = {
    "evport",
    evport_init,
    evport_add,
    evport_del,
    evport_dispatch,
    evport_dealloc,
    1 /* need reinit */
};

/*
 * Initialize the event port implementation.
 */

static void*
evport_init(struct event_base* base)
{
    struct evport_data* evpd;
    int i;
    /*
     * Disable event ports when this environment variable is set
     */
    if (evutil_getenv("EVENT_NOEVPORT"))
        return (NULL);

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

    if ((evpd->ed_port = port_create()) == -1) {
        free(evpd);
        return (NULL);
    }

    /*
     * Initialize file descriptor structure
     */
    evpd->ed_fds = calloc(DEFAULT_NFDS, sizeof(struct fd_info));
    if (evpd->ed_fds == NULL) {
        close(evpd->ed_port);
        free(evpd);
        return (NULL);
    }
    evpd->ed_nevents = DEFAULT_NFDS;
    for (i = 0; i < EVENTS_PER_GETN; i++)
        evpd->ed_pending[i] = -1;

    evsignal_init(base);

    return (evpd);
}

#ifdef CHECK_INVARIANTS
/*
 * Checks some basic properties about the evport_data structure. Because it
 * checks all file descriptors, this function can be expensive when the maximum
 * file descriptor ever used is rather large.
 */

static void
check_evportop(struct evport_data* evpd)
{
    assert(evpd);
    assert(evpd->ed_nevents > 0);
    assert(evpd->ed_port > 0);
    assert(evpd->ed_fds > 0);

    /*
     * Verify the integrity of the fd_info struct as well as the events to
     * which it points (at least, that they're valid references and correct
     * for their position in the structure).
     */
    int i;
    for (i = 0; i < evpd->ed_nevents; ++i) {
        struct event*    ev;
        struct fd_info*  fdi;

        fdi = &evpd->ed_fds[i];
        if ((ev = fdi->fdi_revt) != NULL) {
            assert(ev->ev_fd == i);
        }
        if ((ev = fdi->fdi_wevt) != NULL) {
            assert(ev->ev_fd == i);
        }
    }
}

/*
 * Verifies very basic integrity of a given port_event.
 */
static void
check_event(port_event_t* pevt)
{
    /*
     * We've only registered for PORT_SOURCE_FD events. The only
     * other thing we can legitimately receive is PORT_SOURCE_ALERT,
     * but since we're not using port_alert either, we can assume
     * PORT_SOURCE_FD.
     */
    assert(pevt->portev_source == PORT_SOURCE_FD);
    assert(pevt->portev_user == NULL);
}

#else
#define check_evportop(epop)
#define check_event(pevt)
#endif /* CHECK_INVARIANTS */

/*
 * Doubles the size of the allocated file descriptor array.
 */
static int
grow(struct evport_data* epdp, int factor)
{
    struct fd_info* tmp;
    int oldsize = epdp->ed_nevents;
    int newsize = factor * oldsize;
    assert(factor > 1);

    check_evportop(epdp);

    tmp = realloc(epdp->ed_fds, sizeof(struct fd_info) * newsize);
    if (NULL == tmp)
        return -1;
    epdp->ed_fds = tmp;
    memset((char*) (epdp->ed_fds + oldsize), 0,
           (newsize - oldsize)*sizeof(struct fd_info));
    epdp->ed_nevents = newsize;

    check_evportop(epdp);

    return 0;
}


/*
 * (Re)associates the given file descriptor with the event port. The OS events
 * are specified (implicitly) from the fd_info struct.
 */
static int
reassociate(struct evport_data* epdp, struct fd_info* fdip, int fd)
{
    int sysevents = FDI_TO_SYSEVENTS(fdip);

    if (sysevents != 0) {
        if (port_associate(epdp->ed_port, PORT_SOURCE_FD,
                           fd, sysevents, NULL) == -1) {
            event_warn("port_associate");
            return (-1);
        }
    }

    check_evportop(epdp);

    return (0);
}

/*
 * Main event loop - polls port_getn for some number of events, and processes
 * them.
 */

static int
evport_dispatch(struct event_base* base, void* arg, struct timeval* tv)
{
    int i, res;
    struct evport_data* epdp = arg;
    port_event_t pevtlist[EVENTS_PER_GETN];

    /*
     * port_getn will block until it has at least nevents events. It will
     * also return how many it's given us (which may be more than we asked
     * for, as long as it's less than our maximum (EVENTS_PER_GETN)) in
     * nevents.
     */
    int nevents = 1;

    /*
     * We have to convert a struct timeval to a struct timespec
     * (only difference is nanoseconds vs. microseconds). If no time-based
     * events are active, we should wait for I/O (and tv == NULL).
     */
    struct timespec ts;
    struct timespec* ts_p = NULL;
    if (tv != NULL) {
        ts.tv_sec = tv->tv_sec;
        ts.tv_nsec = tv->tv_usec * 1000;
        ts_p = &ts;
    }

    /*
     * Before doing anything else, we need to reassociate the events we hit
     * last time which need reassociation. See comment at the end of the
     * loop below.
     */
    for (i = 0; i < EVENTS_PER_GETN; ++i) {
        struct fd_info* fdi = NULL;
        if (epdp->ed_pending[i] != -1) {
            fdi = &(epdp->ed_fds[epdp->ed_pending[i]]);
        }

        if (fdi != NULL && FDI_HAS_EVENTS(fdi)) {
            int fd = FDI_HAS_READ(fdi) ? fdi->fdi_revt->ev_fd :
                     fdi->fdi_wevt->ev_fd;
            reassociate(epdp, fdi, fd);
            epdp->ed_pending[i] = -1;
        }
    }

    if ((res = port_getn(epdp->ed_port, pevtlist, EVENTS_PER_GETN,
                         (unsigned int*) &nevents, ts_p)) == -1) {
        if (errno == EINTR || errno == EAGAIN) {
            evsignal_process(base);
            return (0);
        } else if (errno == ETIME) {
            if (nevents == 0)
                return (0);
        } else {
            event_warn("port_getn");
            return (-1);
        }
    } else if (base->sig.evsignal_caught) {
        evsignal_process(base);
    }

    event_debug(("%s: port_getn reports %d events", __func__, nevents));

    for (i = 0; i < nevents; ++i) {
        struct event* ev;
        struct fd_info* fdi;
        port_event_t* pevt = &pevtlist[i];
        int fd = (int) pevt->portev_object;

        check_evportop(epdp);
        check_event(pevt);
        epdp->ed_pending[i] = fd;

        /*
         * Figure out what kind of event it was
         * (because we have to pass this to the callback)
         */
        res = 0;
        if (pevt->portev_events & POLLIN)
            res |= EV_READ;
        if (pevt->portev_events & POLLOUT)
            res |= EV_WRITE;

        /*
         * Check for the error situations or a hangup situation
         */
        if (pevt->portev_events & (POLLERR | POLLHUP | POLLNVAL))
            res |= EV_READ | EV_WRITE;

        assert(epdp->ed_nevents > fd);
        fdi = &(epdp->ed_fds[fd]);

        /*
         * We now check for each of the possible events (READ
         * or WRITE).  Then, we activate the event (which will
         * cause its callback to be executed).
         */

        if ((res & EV_READ) && ((ev = fdi->fdi_revt) != NULL)) {
            event_active(ev, res, 1);
        }

        if ((res & EV_WRITE) && ((ev = fdi->fdi_wevt) != NULL)) {
            event_active(ev, res, 1);
        }
    } /* end of all events gotten */

    check_evportop(epdp);

    return (0);
}


/*
 * Adds the given event (so that you will be notified when it happens via
 * the callback function).
 */

static int
evport_add(void* arg, struct event* ev)
{
    struct evport_data* evpd = arg;
    struct fd_info* fdi;
    int factor;

    check_evportop(evpd);

    /*
     * Delegate, if it's not ours to handle.
     */
    if (ev->ev_events & EV_SIGNAL)
        return (evsignal_add(ev));

    /*
     * If necessary, grow the file descriptor info table
     */

    factor = 1;
    while (ev->ev_fd >= factor * evpd->ed_nevents)
        factor *= 2;

    if (factor > 1) {
        if (-1 == grow(evpd, factor)) {
            return (-1);
        }
    }

    fdi = &evpd->ed_fds[ev->ev_fd];
    if (ev->ev_events & EV_READ)
        fdi->fdi_revt = ev;
    if (ev->ev_events & EV_WRITE)
        fdi->fdi_wevt = ev;

    return reassociate(evpd, fdi, ev->ev_fd);
}

/*
 * Removes the given event from the list of events to wait for.
 */

static int
evport_del(void* arg, struct event* ev)
{
    struct evport_data* evpd = arg;
    struct fd_info* fdi;
    int i;
    int associated = 1;

    check_evportop(evpd);

    /*
     * Delegate, if it's not ours to handle
     */
    if (ev->ev_events & EV_SIGNAL) {
        return (evsignal_del(ev));
    }

    if (evpd->ed_nevents < ev->ev_fd) {
        return (-1);
    }

    for (i = 0; i < EVENTS_PER_GETN; ++i) {
        if (evpd->ed_pending[i] == ev->ev_fd) {
            associated = 0;
            break;
        }
    }

    fdi = &evpd->ed_fds[ev->ev_fd];
    if (ev->ev_events & EV_READ)
        fdi->fdi_revt = NULL;
    if (ev->ev_events & EV_WRITE)
        fdi->fdi_wevt = NULL;

    if (associated) {
        if (!FDI_HAS_EVENTS(fdi) &&
            port_dissociate(evpd->ed_port, PORT_SOURCE_FD,
                            ev->ev_fd) == -1) {
            /*
             * Ignre EBADFD error the fd could have been closed
             * before event_del() was called.
             */
            if (errno != EBADFD) {
                event_warn("port_dissociate");
                return (-1);
            }
        } else {
            if (FDI_HAS_EVENTS(fdi)) {
                return (reassociate(evpd, fdi, ev->ev_fd));
            }
        }
    } else {
        if (fdi->fdi_revt == NULL && fdi->fdi_wevt == NULL) {
            evpd->ed_pending[i] = -1;
        }
    }
    return 0;
}


static void
evport_dealloc(struct event_base* base, void* arg)
{
    struct evport_data* evpd = arg;

    evsignal_dealloc(base);

    close(evpd->ed_port);

    if (evpd->ed_fds)
        free(evpd->ed_fds);
    free(evpd);
}