source: trunk/server/lib/tevent/tevent_poll.c

/*
   Unix SMB/CIFS implementation.
   main select loop and event handling
   Copyright (C) Andrew Tridgell        2003-2005
   Copyright (C) Stefan Metzmacher      2005-2009

     ** NOTE! The following LGPL license applies to the tevent
     ** library. This does NOT imply that all of Samba is released
     ** under the LGPL

   This library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 3 of the License, or (at your option) any later version.

   This library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with this library; if not, see <http://www.gnu.org/licenses/>.
*/

#include "replace.h"
#include "system/filesys.h"
#include "system/select.h"
#include "tevent.h"
#include "tevent_util.h"
#include "tevent_internal.h"

struct poll_event_context {
        /*
         * These two arrays are maintained together.
         */
        struct pollfd *fds;
        struct tevent_fd **fd_events;
        uint64_t num_fds;

        /* information for exiting from the event loop */
        int exit_code;
};

/*
  create a select_event_context structure.
*/
static int poll_event_context_init(struct tevent_context *ev)
{
        struct poll_event_context *poll_ev;

        poll_ev = talloc_zero(ev, struct poll_event_context);
        if (poll_ev == NULL) {
                return -1;
        }
        ev->additional_data = poll_ev;
        return 0;
}

/*
  destroy an fd_event
*/
static int poll_event_fd_destructor(struct tevent_fd *fde)
{
        struct tevent_context *ev = fde->event_ctx;
        struct poll_event_context *poll_ev = NULL;
        struct tevent_fd *moved_fde;
        uint64_t del_idx = fde->additional_flags;

        if (ev == NULL) {
                goto done;
        }

        poll_ev = talloc_get_type_abort(
                ev->additional_data, struct poll_event_context);

        moved_fde = poll_ev->fd_events[poll_ev->num_fds-1];
        poll_ev->fd_events[del_idx] = moved_fde;
        poll_ev->fds[del_idx] = poll_ev->fds[poll_ev->num_fds-1];
        moved_fde->additional_flags = del_idx;

        poll_ev->num_fds -= 1;
done:
        return tevent_common_fd_destructor(fde);
}

/*
  add a fd based event
  return NULL on failure (memory allocation error)
*/
static struct tevent_fd *poll_event_add_fd(struct tevent_context *ev,
                                           TALLOC_CTX *mem_ctx,
                                           int fd, uint16_t flags,
                                           tevent_fd_handler_t handler,
                                           void *private_data,
                                           const char *handler_name,
                                           const char *location)
{
        struct poll_event_context *poll_ev = talloc_get_type_abort(
                ev->additional_data, struct poll_event_context);
        struct pollfd *pfd;
        struct tevent_fd *fde;

        fde = tevent_common_add_fd(ev, mem_ctx, fd, flags,
                                   handler, private_data,
                                   handler_name, location);
        if (fde == NULL) {
                return NULL;
        }

        /* we allocate 16 slots to avoid a lot of reallocations */
        if (talloc_array_length(poll_ev->fds) == poll_ev->num_fds) {
                struct pollfd *tmp_fds;
                struct tevent_fd **tmp_fd_events;
                tmp_fds = talloc_realloc(
                        poll_ev, poll_ev->fds, struct pollfd,
                        poll_ev->num_fds + 16);
                if (tmp_fds == NULL) {
                        TALLOC_FREE(fde);
                        return NULL;
                }
                poll_ev->fds = tmp_fds;

                tmp_fd_events = talloc_realloc(
                        poll_ev, poll_ev->fd_events, struct tevent_fd *,
                        poll_ev->num_fds + 16);
                if (tmp_fd_events == NULL) {
                        TALLOC_FREE(fde);
                        return NULL;
                }
                poll_ev->fd_events = tmp_fd_events;
        }

        pfd = &poll_ev->fds[poll_ev->num_fds];

        pfd->fd = fd;

        pfd->events = 0;
        pfd->revents = 0;

        if (flags & TEVENT_FD_READ) {
                pfd->events |= (POLLIN|POLLHUP);
        }
        if (flags & TEVENT_FD_WRITE) {
                pfd->events |= (POLLOUT);
        }

        fde->additional_flags = poll_ev->num_fds;
        poll_ev->fd_events[poll_ev->num_fds] = fde;

        poll_ev->num_fds += 1;

        talloc_set_destructor(fde, poll_event_fd_destructor);

        return fde;
}

/*
  set the fd event flags
*/
static void poll_event_set_fd_flags(struct tevent_fd *fde, uint16_t flags)
{
        struct poll_event_context *poll_ev = talloc_get_type_abort(
                fde->event_ctx->additional_data, struct poll_event_context);
        uint64_t idx = fde->additional_flags;
        uint16_t pollflags = 0;

        if (flags & TEVENT_FD_READ) {
                pollflags |= (POLLIN|POLLHUP);
        }
        if (flags & TEVENT_FD_WRITE) {
                pollflags |= (POLLOUT);
        }

        poll_ev->fds[idx].events = pollflags;

        fde->flags = flags;
}

/*
  event loop handling using select()
*/
static int poll_event_loop_poll(struct tevent_context *ev,
                                struct timeval *tvalp)
{
        struct poll_event_context *poll_ev = talloc_get_type_abort(
                ev->additional_data, struct poll_event_context);
        struct tevent_fd *fde;
        int pollrtn;
        int timeout = -1;

        if (ev->signal_events && tevent_common_check_signal(ev)) {
                return 0;
        }

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

        pollrtn = poll(poll_ev->fds, poll_ev->num_fds, timeout);

        if (pollrtn == -1 && errno == EINTR && ev->signal_events) {
                tevent_common_check_signal(ev);
                return 0;
        }

        if (pollrtn == -1 && errno == EBADF) {
                /* the socket is dead! this should never
                   happen as the socket should have first been
                   made readable and that should have removed
                   the event, so this must be a bug. This is a
                   fatal error. */
                tevent_debug(ev, TEVENT_DEBUG_FATAL,
                             "ERROR: EBADF on poll_event_loop_once\n");
                poll_ev->exit_code = EBADF;
                return -1;
        }

        if (pollrtn == 0 && tvalp) {
                /* we don't care about a possible delay here */
                tevent_common_loop_timer_delay(ev);
                return 0;
        }

        if (pollrtn > 0) {
                /* at least one file descriptor is ready - check
                   which ones and call the handler, being careful to allow
                   the handler to remove itself when called */
                for (fde = ev->fd_events; fde; fde = fde->next) {
                        struct pollfd *pfd;
                        uint64_t pfd_idx = fde->additional_flags;
                        uint16_t flags = 0;

                        pfd = &poll_ev->fds[pfd_idx];

                        if (pfd->revents & (POLLHUP|POLLERR)) {
                                /* If we only wait for TEVENT_FD_WRITE, we
                                   should not tell the event handler about it,
                                   and remove the writable flag, as we only
                                   report errors when waiting for read events
                                   to match the select behavior. */
                                if (!(fde->flags & TEVENT_FD_READ)) {
                                        TEVENT_FD_NOT_WRITEABLE(fde);
                                        continue;
                                }
                                flags |= TEVENT_FD_READ;
                        }
                        if (pfd->revents & POLLIN) {
                                flags |= TEVENT_FD_READ;
                        }
                        if (pfd->revents & POLLOUT) {
                                flags |= TEVENT_FD_WRITE;
                        }
                        if (flags != 0) {
                                fde->handler(ev, fde, flags,
                                             fde->private_data);
                                break;
                        }
                }
        }

        return 0;
}

/*
  do a single event loop using the events defined in ev
*/
static int poll_event_loop_once(struct tevent_context *ev,
                                const char *location)
{
        struct timeval tval;

        if (ev->signal_events &&
            tevent_common_check_signal(ev)) {
                return 0;
        }

        if (ev->immediate_events &&
            tevent_common_loop_immediate(ev)) {
                return 0;
        }

        tval = tevent_common_loop_timer_delay(ev);
        if (tevent_timeval_is_zero(&tval)) {
                return 0;
        }

        return poll_event_loop_poll(ev, &tval);
}

static const struct tevent_ops poll_event_ops = {
        .context_init           = poll_event_context_init,
        .add_fd                 = poll_event_add_fd,
        .set_fd_close_fn        = tevent_common_fd_set_close_fn,
        .get_fd_flags           = tevent_common_fd_get_flags,
        .set_fd_flags           = poll_event_set_fd_flags,
        .add_timer              = tevent_common_add_timer,
        .schedule_immediate     = tevent_common_schedule_immediate,
        .add_signal             = tevent_common_add_signal,
        .loop_once              = poll_event_loop_once,
        .loop_wait              = tevent_common_loop_wait,
};

_PRIVATE_ bool tevent_poll_init(void)
{
        return tevent_register_backend("poll", &poll_event_ops);
}