tevent: release 0.16.1

[Samba.git] / 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 {
        /* a pointer back to the generic event_context */
        struct tevent_context *ev;

        /*
         * one or more events were deleted or disabled
         */
        bool deleted;

        /*
         * These two arrays are maintained together.
         *
         * The following is always true:
         * num_fds <= num_fdes
         *
         * new 'fresh' elements are added at the end
         * of the 'fdes' array and picked up later
         * to the 'fds' array in poll_event_sync_arrays()
         * before the poll() syscall.
         */
        struct pollfd *fds;
        size_t num_fds;
        struct tevent_fd **fdes;
        size_t num_fdes;

        /*
         * use tevent_common_wakeup(ev) to wake the poll() thread
         */
        bool use_mt_mode;
};

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

        /*
         * we might be called during tevent_re_initialise()
         * which means we need to free our old additional_data
         * in order to detach old fd events from the
         * poll_ev->fresh list
         */
        TALLOC_FREE(ev->additional_data);

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

static int poll_event_context_init_mt(struct tevent_context *ev)
{
        struct poll_event_context *poll_ev;
        int ret;

        ret = poll_event_context_init(ev);
        if (ret == -1) {
                return ret;
        }

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

        ret = tevent_common_wakeup_init(ev);
        if (ret != 0) {
                return ret;
        }

        poll_ev->use_mt_mode = true;

        return 0;
}

static void poll_event_wake_pollthread(struct poll_event_context *poll_ev)
{
        if (!poll_ev->use_mt_mode) {
                return;
        }
        tevent_common_wakeup(poll_ev->ev);
}

/*
  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;
        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);

        if (del_idx == UINT64_MAX) {
                goto done;
        }

        poll_ev->fdes[del_idx] = NULL;
        poll_ev->deleted = true;
        poll_event_wake_pollthread(poll_ev);
done:
        return tevent_common_fd_destructor(fde);
}

static void poll_event_schedule_immediate(struct tevent_immediate *im,
                                          struct tevent_context *ev,
                                          tevent_immediate_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);

        tevent_common_schedule_immediate(im, ev, handler, private_data,
                                         handler_name, location);
        poll_event_wake_pollthread(poll_ev);
}

/*
  Private function called by "standard" backend fallback.
  Note this only allows fallback to "poll" backend, not "poll-mt".
*/
_PRIVATE_ bool tevent_poll_event_add_fd_internal(struct tevent_context *ev,
                                                 struct tevent_fd *fde)
{
        struct poll_event_context *poll_ev = talloc_get_type_abort(
                ev->additional_data, struct poll_event_context);
        uint64_t fde_idx = UINT64_MAX;
        size_t num_fdes;

        fde->additional_flags = UINT64_MAX;
        tevent_common_fd_mpx_reinit(fde);
        talloc_set_destructor(fde, poll_event_fd_destructor);

        if (fde->flags == 0) {
                /*
                 * Nothing more to do...
                 */
                return true;
        }

        /*
         * We need to add it to the end of the 'fdes' array.
         */
        num_fdes = poll_ev->num_fdes + 1;
        if (num_fdes > talloc_array_length(poll_ev->fdes)) {
                struct tevent_fd **tmp_fdes = NULL;
                size_t array_length;

                array_length = (num_fdes + 15) & ~15; /* round up to 16 */

                tmp_fdes = talloc_realloc(poll_ev,
                                          poll_ev->fdes,
                                          struct tevent_fd *,
                                          array_length);
                if (tmp_fdes == NULL) {
                        return false;
                }
                poll_ev->fdes = tmp_fdes;
        }

        fde_idx = poll_ev->num_fdes;
        fde->additional_flags = fde_idx;
        poll_ev->fdes[fde_idx] = fde;
        poll_ev->num_fdes++;

        return true;
}

/*
  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 tevent_fd *fde;
        bool ok;

        if (fd < 0) {
                return NULL;
        }

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

        ok = tevent_poll_event_add_fd_internal(ev, fde);
        if (!ok) {
                TALLOC_FREE(fde);
                return NULL;
        }
        poll_event_wake_pollthread(poll_ev);

        /*
         * poll_event_loop_poll will take care of the rest in
         * poll_event_setup_fresh
         */
        return fde;
}

/*
  map from TEVENT_FD_* to POLLIN/POLLOUT
*/
static uint16_t poll_map_flags(uint16_t flags)
{
        uint16_t pollflags = 0;

        /*
         * we do not need to specify POLLERR | POLLHUP
         * they are always reported.
         */

        if (flags & TEVENT_FD_READ) {
                pollflags |= POLLIN;
#ifdef POLLRDHUP
                /*
                 * Note that at least on Linux
                 * POLLRDHUP always returns
                 * POLLIN in addition, so this
                 * is not strictly needed, but
                 * we want to make it explicit.
                 */
                pollflags |= POLLRDHUP;
#endif
        }
        if (flags & TEVENT_FD_WRITE) {
                pollflags |= POLLOUT;
        }
        if (flags & TEVENT_FD_ERROR) {
#ifdef POLLRDHUP
                pollflags |= POLLRDHUP;
#endif
        }

        return pollflags;
}

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

        if (ev == NULL) {
                return;
        }

        if (fde->flags == flags) {
                return;
        }

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

        fde->flags = flags;

        if (idx == UINT64_MAX) {
                /*
                 * We move it between the fresh and disabled lists.
                 */
                tevent_poll_event_add_fd_internal(ev, fde);
                poll_event_wake_pollthread(poll_ev);
                return;
        }

        if (fde->flags == 0) {
                /*
                 * We need to remove it from the array
                 * and move it to the disabled list.
                 */
                poll_ev->fdes[idx] = NULL;
                poll_ev->deleted = true;
                fde->additional_flags = UINT64_MAX;
                poll_event_wake_pollthread(poll_ev);
                return;
        }

        if (idx >= poll_ev->num_fds) {
                /*
                 * Not yet added to the
                 * poll_ev->fds array.
                 */
                poll_event_wake_pollthread(poll_ev);
                return;
        }

        poll_ev->fds[idx].events = poll_map_flags(flags);

        poll_event_wake_pollthread(poll_ev);
}

static bool poll_event_sync_arrays(struct tevent_context *ev,
                                   struct poll_event_context *poll_ev)
{
        size_t i;
        size_t array_length;

        if (poll_ev->deleted) {

                for (i=0; i < poll_ev->num_fds;) {
                        struct tevent_fd *fde = poll_ev->fdes[i];
                        size_t ci;

                        if (fde != NULL) {
                                i++;
                                continue;
                        }

                        /*
                         * This fde was talloc_free()'ed. Delete it
                         * from the arrays
                         */
                        poll_ev->num_fds -= 1;
                        ci = poll_ev->num_fds;
                        if (ci > i) {
                                poll_ev->fds[i] = poll_ev->fds[ci];
                                poll_ev->fdes[i] = poll_ev->fdes[ci];
                                if (poll_ev->fdes[i] != NULL) {
                                        poll_ev->fdes[i]->additional_flags = i;
                                }
                        }
                        poll_ev->fds[ci] = (struct pollfd) { .fd = -1 };
                        poll_ev->fdes[ci] = NULL;
                }
                poll_ev->deleted = false;
        }

        if (poll_ev->num_fds == poll_ev->num_fdes) {
                return true;
        }

        /*
         * Recheck the size of both arrays and make sure
         * poll_fd->fds array has at least the size of the
         * in use poll_ev->fdes array.
         */
        if (poll_ev->num_fdes > talloc_array_length(poll_ev->fds)) {
                struct pollfd *tmp_fds = NULL;

                /*
                 * Make sure both allocated the same length.
                 */
                array_length = talloc_array_length(poll_ev->fdes);

                tmp_fds = talloc_realloc(poll_ev,
                                         poll_ev->fds,
                                         struct pollfd,
                                         array_length);
                if (tmp_fds == NULL) {
                        return false;
                }
                poll_ev->fds = tmp_fds;
        }

        /*
         * Now setup the new elements.
         */
        for (i = poll_ev->num_fds; i < poll_ev->num_fdes; i++) {
                struct tevent_fd *fde = poll_ev->fdes[i];
                struct pollfd *pfd = &poll_ev->fds[poll_ev->num_fds];

                if (fde == NULL) {
                        continue;
                }

                if (i > poll_ev->num_fds) {
                        poll_ev->fdes[poll_ev->num_fds] = fde;
                        fde->additional_flags = poll_ev->num_fds;
                        poll_ev->fdes[i] = NULL;
                }

                pfd->fd = fde->fd;
                pfd->events = poll_map_flags(fde->flags);
                pfd->revents = 0;

                poll_ev->num_fds += 1;
        }
        /* Both are in sync again */
        poll_ev->num_fdes = poll_ev->num_fds;

        /*
         * Check if we should shrink the arrays
         * But keep at least 16 elements.
         */

        array_length = (poll_ev->num_fds + 15) & ~15; /* round up to 16 */
        array_length = MAX(array_length, 16);
        if (array_length < talloc_array_length(poll_ev->fdes)) {
                struct tevent_fd **tmp_fdes = NULL;
                struct pollfd *tmp_fds = NULL;

                tmp_fdes = talloc_realloc(poll_ev,
                                          poll_ev->fdes,
                                          struct tevent_fd *,
                                          array_length);
                if (tmp_fdes == NULL) {
                        return false;
                }
                poll_ev->fdes = tmp_fdes;

                tmp_fds = talloc_realloc(poll_ev,
                                         poll_ev->fds,
                                         struct pollfd,
                                         array_length);
                if (tmp_fds == NULL) {
                        return false;
                }
                poll_ev->fds = tmp_fds;
        }

        return true;
}

/*
  event loop handling using poll()
*/
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);
        int pollrtn;
        int timeout = -1;
        int poll_errno;
        struct tevent_fd *fde = NULL;
        struct tevent_fd *next = NULL;
        unsigned i;
        bool ok;

        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;
        }

        ok = poll_event_sync_arrays(ev, poll_ev);
        if (!ok) {
                return -1;
        }

        tevent_trace_point_callback(poll_ev->ev, TEVENT_TRACE_BEFORE_WAIT);
        pollrtn = poll(poll_ev->fds, poll_ev->num_fds, timeout);
        poll_errno = errno;
        tevent_trace_point_callback(poll_ev->ev, TEVENT_TRACE_AFTER_WAIT);

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

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

        if (pollrtn <= 0) {
                /*
                 * No fd's ready
                 */
                return 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 = next) {
                uint64_t idx = fde->additional_flags;
                struct pollfd *pfd;
                uint16_t flags = 0;

                next = fde->next;

                if (idx == UINT64_MAX) {
                        continue;
                }

                pfd = &poll_ev->fds[idx];

                if (pfd->revents & POLLNVAL) {
                        /*
                         * 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.
                         *
                         * We ignore it here to match the epoll
                         * behavior.
                         */
                        tevent_debug(ev, TEVENT_DEBUG_ERROR,
                                     "POLLNVAL on fde[%p] fd[%d] - disabling\n",
                                     fde, pfd->fd);
                        poll_ev->fdes[idx] = NULL;
                        poll_ev->deleted = true;
                        tevent_common_fd_disarm(fde);
                        continue;
                }

#ifdef POLLRDHUP
#define __POLL_RETURN_ERROR_FLAGS (POLLHUP|POLLERR|POLLRDHUP)
#else
#define __POLL_RETURN_ERROR_FLAGS (POLLHUP|POLLERR)
#endif

                if (pfd->revents & __POLL_RETURN_ERROR_FLAGS) {
                        /*
                         * 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
                         * or explicit for errors.
                         */
                        if (!(fde->flags & (TEVENT_FD_READ|TEVENT_FD_ERROR)))
                        {
                                TEVENT_FD_NOT_WRITEABLE(fde);
                                continue;
                        }
                        if (fde->flags & TEVENT_FD_ERROR) {
                                flags |= TEVENT_FD_ERROR;
                        }
                        if (fde->flags & TEVENT_FD_READ) {
                                flags |= TEVENT_FD_READ;
                        }
                }
                if (pfd->revents & POLLIN) {
                        flags |= TEVENT_FD_READ;
                }
                if (pfd->revents & POLLOUT) {
                        flags |= TEVENT_FD_WRITE;
                }
                /*
                 * Note that fde->flags could be changed when using
                 * the poll_mt backend together with threads,
                 * that why we need to check pfd->revents and fde->flags
                 */
                flags &= fde->flags;
                if (flags != 0) {
                        DLIST_DEMOTE(ev->fd_events, fde);
                        return tevent_common_invoke_fd_handler(fde, flags, NULL);
                }
        }

        for (i = 0; i < poll_ev->num_fds; i++) {
                if (poll_ev->fds[i].revents & POLLNVAL) {
                        /*
                         * 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 or
                         * a race in the poll_mt usage.
                         */
                        fde = poll_ev->fdes[i];
                        tevent_debug(ev, TEVENT_DEBUG_WARNING,
                                     "POLLNVAL on dangling fd[%d] fde[%p] - disabling\n",
                                     poll_ev->fds[i].fd, fde);
                        poll_ev->fdes[i] = NULL;
                        poll_ev->deleted = true;
                        if (fde != NULL) {
                                tevent_common_fd_disarm(fde);
                        }
                }
        }

        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->threaded_contexts != NULL) {
                tevent_common_threaded_activate_immediate(ev);
        }

        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_v2,
        .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);
}

static const struct tevent_ops poll_event_mt_ops = {
        .context_init           = poll_event_context_init_mt,
        .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_v2,
        .schedule_immediate     = poll_event_schedule_immediate,
        .add_signal             = tevent_common_add_signal,
        .loop_once              = poll_event_loop_once,
        .loop_wait              = tevent_common_loop_wait,
};

_PRIVATE_ bool tevent_poll_mt_init(void)
{
        return tevent_register_backend("poll_mt", &poll_event_mt_ops);
}