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/_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 (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);
}