]> git.ipfire.org Git - thirdparty/samba.git/commitdiff
tevent: rewrite/simplify tevent_poll and maintain ev->fd_events correctly
authorStefan Metzmacher <metze@samba.org>
Mon, 18 Jun 2018 17:49:52 +0000 (19:49 +0200)
committerRalph Boehme <slow@samba.org>
Wed, 11 Jul 2018 21:04:17 +0000 (23:04 +0200)
The following patches will rely on having all valid fd events in
ev->fd_events, even if they are temporary disabled with
tevent_set_fd_flags(fde, 0);

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Ralph Boehme <slow@samba.org>
lib/tevent/tevent_internal.h
lib/tevent/tevent_poll.c
lib/tevent/tevent_standard.c

index ec3955e70a492dfb340328dc1fdbd75af9b053bd..692e8d0e0a2d56c5ebef8859a5ae3295c5b5aedf 100644 (file)
@@ -377,7 +377,7 @@ void tevent_cleanup_pending_signal_handlers(struct tevent_signal *se);
 
 bool tevent_standard_init(void);
 bool tevent_poll_init(void);
-void tevent_poll_event_add_fd_internal(struct tevent_context *ev,
+bool tevent_poll_event_add_fd_internal(struct tevent_context *ev,
                                       struct tevent_fd *fde);
 bool tevent_poll_mt_init(void);
 #ifdef HAVE_EPOLL
index 23b5779d70486bf540899b9af1681549262ab5b2..282f3cf3082c32dfb0ba1359289554a34d242940 100644 (file)
@@ -33,15 +33,6 @@ struct poll_event_context {
        /* a pointer back to the generic event_context */
        struct tevent_context *ev;
 
-       /*
-        * A DLIST for fresh fde's added by poll_event_add_fd but not
-        * picked up yet by poll_event_loop_once
-        */
-       struct tevent_fd *fresh;
-       /*
-        * A DLIST for disabled fde's.
-        */
-       struct tevent_fd *disabled;
        /*
         * one or more events were deleted or disabled
         */
@@ -49,10 +40,19 @@ struct poll_event_context {
 
        /*
         * 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;
-       unsigned num_fds;
+       size_t num_fdes;
 
        /*
         * use tevent_common_wakeup(ev) to wake the poll() thread
@@ -60,24 +60,6 @@ struct poll_event_context {
        bool use_mt_mode;
 };
 
-static int poll_event_context_destructor(struct poll_event_context *poll_ev)
-{
-       struct tevent_fd *fd, *fn;
-
-       for (fd = poll_ev->fresh; fd; fd = fn) {
-               fn = fd->next;
-               fd->event_ctx = NULL;
-               DLIST_REMOVE(poll_ev->fresh, fd);
-       }
-
-       for (fd = poll_ev->disabled; fd; fd = fn) {
-               fn = fd->next;
-               fd->event_ctx = NULL;
-               DLIST_REMOVE(poll_ev->disabled, fd);
-       }
-       return 0;
-}
-
 /*
   create a poll_event_context structure.
 */
@@ -99,7 +81,6 @@ static int poll_event_context_init(struct tevent_context *ev)
        }
        poll_ev->ev = ev;
        ev->additional_data = poll_ev;
-       talloc_set_destructor(poll_ev, poll_event_context_destructor);
        return 0;
 }
 
@@ -151,10 +132,6 @@ static int poll_event_fd_destructor(struct tevent_fd *fde)
                ev->additional_data, struct poll_event_context);
 
        if (del_idx == UINT64_MAX) {
-               struct tevent_fd **listp =
-                       (struct tevent_fd **)fde->additional_data;
-
-               DLIST_REMOVE((*listp), fde);
                goto done;
        }
 
@@ -184,24 +161,50 @@ static void poll_event_schedule_immediate(struct tevent_immediate *im,
   Private function called by "standard" backend fallback.
   Note this only allows fallback to "poll" backend, not "poll-mt".
 */
-_PRIVATE_ void tevent_poll_event_add_fd_internal(struct tevent_context *ev,
+_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);
-       struct tevent_fd **listp;
+       uint64_t fde_idx = UINT64_MAX;
+       size_t num_fdes;
 
-       if (fde->flags != 0) {
-               listp = &poll_ev->fresh;
-       } else {
-               listp = &poll_ev->disabled;
+       fde->additional_flags = UINT64_MAX;
+       talloc_set_destructor(fde, poll_event_fd_destructor);
+
+       if (fde->flags == 0) {
+               /*
+                * Nothing more to do...
+                */
+               return true;
        }
 
-       fde->additional_flags   = UINT64_MAX;
-       fde->additional_data    = listp;
+       /*
+        * 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;
 
-       DLIST_ADD((*listp), fde);
-       talloc_set_destructor(fde, poll_event_fd_destructor);
+               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;
 }
 
 /*
@@ -219,27 +222,29 @@ static struct tevent_fd *poll_event_add_fd(struct tevent_context *ev,
        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 = talloc(mem_ctx ? mem_ctx : ev, struct tevent_fd);
+       fde = tevent_common_add_fd(ev,
+                                  mem_ctx,
+                                  fd,
+                                  flags,
+                                  handler,
+                                  private_data,
+                                  handler_name,
+                                  location);
        if (fde == NULL) {
                return NULL;
        }
-       fde->event_ctx          = ev;
-       fde->fd                 = fd;
-       fde->flags              = flags;
-       fde->handler            = handler;
-       fde->close_fn           = NULL;
-       fde->private_data       = private_data;
-       fde->handler_name       = handler_name;
-       fde->location           = location;
-       fde->additional_flags   = UINT64_MAX;
-       fde->additional_data    = NULL;
-
-       tevent_poll_event_add_fd_internal(ev, fde);
+
+       ok = tevent_poll_event_add_fd_internal(ev, fde);
+       if (!ok) {
+               TALLOC_FREE(fde);
+               return NULL;
+       }
        poll_event_wake_pollthread(poll_ev);
 
        /*
@@ -262,19 +267,20 @@ static void poll_event_set_fd_flags(struct tevent_fd *fde, uint16_t 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) {
-               struct tevent_fd **listp =
-                       (struct tevent_fd **)fde->additional_data;
-
                /*
                 * We move it between the fresh and disabled lists.
                 */
-               DLIST_REMOVE((*listp), fde);
                tevent_poll_event_add_fd_internal(ev, fde);
                poll_event_wake_pollthread(poll_ev);
                return;
@@ -287,8 +293,16 @@ static void poll_event_set_fd_flags(struct tevent_fd *fde, uint16_t flags)
                 */
                poll_ev->fdes[idx] = NULL;
                poll_ev->deleted = true;
-               DLIST_REMOVE(ev->fd_events, fde);
-               tevent_poll_event_add_fd_internal(ev, fde);
+               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;
        }
@@ -306,17 +320,18 @@ static void poll_event_set_fd_flags(struct tevent_fd *fde, uint16_t flags)
        poll_event_wake_pollthread(poll_ev);
 }
 
-static bool poll_event_setup_fresh(struct tevent_context *ev,
+static bool poll_event_sync_arrays(struct tevent_context *ev,
                                   struct poll_event_context *poll_ev)
 {
-       struct tevent_fd *fde, *next;
-       unsigned num_fresh, num_fds;
+       size_t i;
+       size_t array_length;
 
        if (poll_ev->deleted) {
-               unsigned i;
 
                for (i=0; i < poll_ev->num_fds;) {
-                       fde = poll_ev->fdes[i];
+                       struct tevent_fd *fde = poll_ev->fdes[i];
+                       size_t ci;
+
                        if (fde != NULL) {
                                i++;
                                continue;
@@ -327,61 +342,63 @@ static bool poll_event_setup_fresh(struct tevent_context *ev,
                         * from the arrays
                         */
                        poll_ev->num_fds -= 1;
-                       if (poll_ev->num_fds == i) {
-                               break;
-                       }
-                       poll_ev->fds[i] = poll_ev->fds[poll_ev->num_fds];
-                       poll_ev->fdes[i] = poll_ev->fdes[poll_ev->num_fds];
-                       if (poll_ev->fdes[i] != NULL) {
-                               poll_ev->fdes[i]->additional_flags = i;
+                       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->fresh == NULL) {
+       if (poll_ev->num_fds == poll_ev->num_fdes) {
                return true;
        }
 
-       num_fresh = 0;
-       for (fde = poll_ev->fresh; fde; fde = fde->next) {
-               num_fresh += 1;
-       }
-       num_fds = poll_ev->num_fds + num_fresh;
-
        /*
-        * We check the length of fdes here. It is the last one
-        * enlarged, so if the realloc for poll_fd->fdes fails,
-        * poll_fd->fds will have at least the size of poll_fd->fdes
+        * 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;
 
-       if (num_fds >= talloc_array_length(poll_ev->fdes)) {
-               struct pollfd *tmp_fds;
-               struct tevent_fd **tmp_fdes;
-               unsigned array_length;
-
-               array_length = (num_fds + 15) & ~15; /* round up to 16 */
+               /*
+                * 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);
+               tmp_fds = talloc_realloc(poll_ev,
+                                        poll_ev->fds,
+                                        struct pollfd,
+                                        array_length);
                if (tmp_fds == NULL) {
                        return false;
                }
                poll_ev->fds = tmp_fds;
-
-               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;
        }
 
-       for (fde = poll_ev->fresh; fde; fde = next) {
-               struct pollfd *pfd;
+       /*
+        * 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;
+               }
 
-               pfd = &poll_ev->fds[poll_ev->num_fds];
+               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 = 0;
@@ -394,15 +411,41 @@ static bool poll_event_setup_fresh(struct tevent_context *ev,
                        pfd->events |= (POLLOUT);
                }
 
-               fde->additional_flags = poll_ev->num_fds;
-               poll_ev->fdes[poll_ev->num_fds] = fde;
+               poll_ev->num_fds += 1;
+       }
+       /* Both are in sync again */
+       poll_ev->num_fdes = poll_ev->num_fds;
 
-               next = fde->next;
-               DLIST_REMOVE(poll_ev->fresh, fde);
-               DLIST_ADD(ev->fd_events, fde);
+       /*
+        * Check if we should shrink the arrays
+        * But keep at least 16 elements.
+        */
 
-               poll_ev->num_fds += 1;
+       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;
 }
 
@@ -420,6 +463,7 @@ static int poll_event_loop_poll(struct tevent_context *ev,
        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;
@@ -430,7 +474,8 @@ static int poll_event_loop_poll(struct tevent_context *ev,
                timeout += (tvalp->tv_usec + 999) / 1000;
        }
 
-       if (!poll_event_setup_fresh(ev, poll_ev)) {
+       ok = poll_event_sync_arrays(ev, poll_ev);
+       if (!ok) {
                return -1;
        }
 
@@ -580,33 +625,6 @@ static int poll_event_loop_once(struct tevent_context *ev,
        return poll_event_loop_poll(ev, &tval);
 }
 
-static int poll_event_loop_wait(struct tevent_context *ev,
-                               const char *location)
-{
-       struct poll_event_context *poll_ev = talloc_get_type_abort(
-               ev->additional_data, struct poll_event_context);
-
-       /*
-        * loop as long as we have events pending
-        */
-       while (tevent_common_have_events(ev) ||
-              poll_ev->fresh ||
-              poll_ev->disabled) {
-               int ret;
-               ret = _tevent_loop_once(ev, location);
-               if (ret != 0) {
-                       tevent_debug(ev, TEVENT_DEBUG_FATAL,
-                                    "_tevent_loop_once() failed: %d - %s\n",
-                                    ret, strerror(errno));
-                       return ret;
-               }
-       }
-
-       tevent_debug(ev, TEVENT_DEBUG_WARNING,
-                    "poll_event_loop_wait() out of events\n");
-       return 0;
-}
-
 static const struct tevent_ops poll_event_ops = {
        .context_init           = poll_event_context_init,
        .add_fd                 = poll_event_add_fd,
@@ -617,7 +635,7 @@ static const struct tevent_ops poll_event_ops = {
        .schedule_immediate     = tevent_common_schedule_immediate,
        .add_signal             = tevent_common_add_signal,
        .loop_once              = poll_event_loop_once,
-       .loop_wait              = poll_event_loop_wait,
+       .loop_wait              = tevent_common_loop_wait,
 };
 
 _PRIVATE_ bool tevent_poll_init(void)
@@ -635,7 +653,7 @@ static const struct tevent_ops poll_event_mt_ops = {
        .schedule_immediate     = poll_event_schedule_immediate,
        .add_signal             = tevent_common_add_signal,
        .loop_once              = poll_event_loop_once,
-       .loop_wait              = poll_event_loop_wait,
+       .loop_wait              = tevent_common_loop_wait,
 };
 
 _PRIVATE_ bool tevent_poll_mt_init(void)
index 30e9b91a865161892b3fc2a16ea9d2c8e49ecde1..38720204e021d606184e473bac1a67e6b5cc0de3 100644 (file)
@@ -63,7 +63,6 @@ static bool std_fallback_to_poll(struct tevent_context *ev, bool replay)
                struct std_event_glue);
        int ret;
        struct tevent_fd *fde;
-       struct tevent_fd *fde_next;
 
        glue->fallback_replay = replay;
 
@@ -86,17 +85,14 @@ static bool std_fallback_to_poll(struct tevent_context *ev, bool replay)
         * Now we have to change all the existing file descriptor
         * events from the epoll backend to the poll backend.
         */
-       for (fde = ev->fd_events; fde; fde = fde_next) {
-               /*
-                * We must remove this fde off the ev->fd_events list.
-                */
-               fde_next = fde->next;
-
-               /* Remove from the ev->fd_events list. */
-               DLIST_REMOVE(ev->fd_events, fde);
+       for (fde = ev->fd_events; fde; fde = fde->next) {
+               bool ok;
 
                /* Re-add this event as a poll backend event. */
-               tevent_poll_event_add_fd_internal(ev, fde);
+               ok = tevent_poll_event_add_fd_internal(ev, fde);
+               if (!ok) {
+                       return false;
+               }
        }
 
        return true;