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 (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;

                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);
}