Line data    Source code

       1             : /* 
       2             :    Unix SMB/CIFS implementation.
       3             :    main select loop and event handling
       4             :    Copyright (C) Stefan Metzmacher      2013
       5             :    Copyright (C) Jeremy Allison         2013
       6             : 
       7             :      ** NOTE! The following LGPL license applies to the tevent
       8             :      ** library. This does NOT imply that all of Samba is released
       9             :      ** under the LGPL
      10             : 
      11             :    This library is free software; you can redistribute it and/or
      12             :    modify it under the terms of the GNU Lesser General Public
      13             :    License as published by the Free Software Foundation; either
      14             :    version 3 of the License, or (at your option) any later version.
      15             : 
      16             :    This library is distributed in the hope that it will be useful,
      17             :    but WITHOUT ANY WARRANTY; without even the implied warranty of
      18             :    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
      19             :    Lesser General Public License for more details.
      20             : 
      21             :    You should have received a copy of the GNU Lesser General Public
      22             :    License along with this library; if not, see <http://www.gnu.org/licenses/>.
      23             : */
      24             : 
      25             : /*
      26             :   This is SAMBA's default event loop code
      27             : 
      28             :   - we try to use epoll if configure detected support for it
      29             :     otherwise we use poll()
      30             :   - if epoll is broken on the system or the kernel doesn't support it
      31             :     at runtime we fallback to poll()
      32             : */
      33             : 
      34             : #include "replace.h"
      35             : #include "tevent.h"
      36             : #include "tevent_util.h"
      37             : #include "tevent_internal.h"
      38             : 
      39             : struct std_event_glue {
      40             :         const struct tevent_ops *epoll_ops;
      41             :         const struct tevent_ops *poll_ops;
      42             :         struct tevent_ops *glue_ops;
      43             :         bool fallback_replay;
      44             : };
      45             : 
      46             : static int std_event_context_init(struct tevent_context *ev);
      47             : 
      48             : static const struct tevent_ops std_event_ops = {
      49             :         .context_init           = std_event_context_init,
      50             : };
      51             : 
      52             : /*
      53             :   If this function gets called. epoll failed at runtime.
      54             :   Move us to using poll instead. If we return false here,
      55             :   caller should abort().
      56             : */
      57             : #ifdef HAVE_EPOLL
      58           5 : static bool std_fallback_to_poll(struct tevent_context *ev, bool replay)
      59             : {
      60           5 :         void *glue_ptr = talloc_parent(ev->ops);
      61           0 :         struct std_event_glue *glue =
      62           5 :                 talloc_get_type_abort(glue_ptr,
      63             :                 struct std_event_glue);
      64           0 :         int ret;
      65           0 :         struct tevent_fd *fde;
      66             : 
      67           5 :         glue->fallback_replay = replay;
      68             : 
      69             :         /* First switch all the ops to poll. */
      70           5 :         glue->epoll_ops = NULL;
      71             : 
      72             :         /*
      73             :          * Set custom_ops the same as poll.
      74             :          */
      75           5 :         *glue->glue_ops = *glue->poll_ops;
      76           5 :         glue->glue_ops->context_init = std_event_context_init;
      77             : 
      78             :         /* Next initialize the poll backend. */
      79           5 :         ret = glue->poll_ops->context_init(ev);
      80           5 :         if (ret != 0) {
      81           0 :                 return false;
      82             :         }
      83             : 
      84             :         /*
      85             :          * Now we have to change all the existing file descriptor
      86             :          * events from the epoll backend to the poll backend.
      87             :          */
      88          10 :         for (fde = ev->fd_events; fde; fde = fde->next) {
      89           0 :                 bool ok;
      90             : 
      91             :                 /* Re-add this event as a poll backend event. */
      92           5 :                 ok = tevent_poll_event_add_fd_internal(ev, fde);
      93           5 :                 if (!ok) {
      94           0 :                         return false;
      95             :                 }
      96             :         }
      97             : 
      98           5 :         return true;
      99             : }
     100             : #endif
     101             : 
     102   416626754 : static int std_event_loop_once(struct tevent_context *ev, const char *location)
     103             : {
     104   416626754 :         void *glue_ptr = talloc_parent(ev->ops);
     105    14834114 :         struct std_event_glue *glue =
     106   416626754 :                 talloc_get_type_abort(glue_ptr,
     107             :                 struct std_event_glue);
     108    14834116 :         int ret;
     109             : 
     110   416626756 :         ret = glue->epoll_ops->loop_once(ev, location);
     111             :         /*
     112             :          * If the above hasn't panicked due to an epoll interface failure,
     113             :          * std_fallback_to_poll() wasn't called, and hasn't cleared epoll_ops to
     114             :          * signify fallback to poll_ops.
     115             :          */
     116   416531287 :         if (glue->epoll_ops != NULL) {
     117             :                 /* No fallback */
     118   401698936 :                 return ret;
     119             :         }
     120             : 
     121           0 :         if (!glue->fallback_replay) {
     122             :                 /*
     123             :                  * The problem happened while modifying an event.
     124             :                  * An event handler was triggered in this case
     125             :                  * and there is no need to call loop_once() again.
     126             :                  */
     127           0 :                 return ret;
     128             :         }
     129             : 
     130           0 :         return glue->poll_ops->loop_once(ev, location);
     131             : }
     132             : 
     133       95291 : static int std_event_loop_wait(struct tevent_context *ev, const char *location)
     134             : {
     135       95291 :         void *glue_ptr = talloc_parent(ev->ops);
     136        1755 :         struct std_event_glue *glue =
     137       95291 :                 talloc_get_type_abort(glue_ptr,
     138             :                 struct std_event_glue);
     139        1755 :         int ret;
     140             : 
     141       95291 :         ret = glue->epoll_ops->loop_wait(ev, location);
     142             :         /*
     143             :          * If the above hasn't panicked due to an epoll interface failure,
     144             :          * std_fallback_to_poll() wasn't called, and hasn't cleared epoll_ops to
     145             :          * signify fallback to poll_ops.
     146             :          */
     147          10 :         if (glue->epoll_ops != NULL) {
     148             :                 /* No fallback */
     149           1 :                 return ret;
     150             :         }
     151             : 
     152           0 :         return glue->poll_ops->loop_wait(ev, location);
     153             : }
     154             : /*
     155             :   Initialize the epoll backend and allow it to call a
     156             :   switch function if epoll fails at runtime.
     157             : */
     158    83086477 : static int std_event_context_init(struct tevent_context *ev)
     159             : {
     160     3110090 :         struct std_event_glue *glue;
     161     3110090 :         int ret;
     162             : 
     163             :         /*
     164             :          * If this is the first initialization
     165             :          * we need to set up the allocated ops
     166             :          * pointers.
     167             :          */
     168             : 
     169    83086477 :         if (ev->ops->loop_once == NULL) {
     170    82990998 :                 glue = talloc_zero(ev, struct std_event_glue);
     171    82990998 :                 if (glue == NULL) {
     172           0 :                         return -1;
     173             :                 }
     174             : 
     175    82990998 :                 glue->epoll_ops = tevent_find_ops_byname("epoll");
     176             : 
     177    82990998 :                 glue->poll_ops = tevent_find_ops_byname("poll");
     178    82990998 :                 if (glue->poll_ops == NULL) {
     179           0 :                         return -1;
     180             :                 }
     181             : 
     182             :                 /*
     183             :                  * Allocate space for our custom ops.
     184             :                  * Allocate as a child of our epoll_ops pointer
     185             :                  * so we can easily get to it using talloc_parent.
     186             :                  */
     187    82990998 :                 glue->glue_ops = talloc_zero(glue, struct tevent_ops);
     188    82990998 :                 if (glue->glue_ops == NULL) {
     189           0 :                         talloc_free(glue);
     190           0 :                         return -1;
     191             :                 }
     192             : 
     193    82990998 :                 ev->ops = glue->glue_ops;
     194             :         } else {
     195       95479 :                 void *glue_ptr = talloc_parent(ev->ops);
     196       95479 :                 glue = talloc_get_type_abort(glue_ptr, struct std_event_glue);
     197             :         }
     198             : 
     199    83086477 :         if (glue->epoll_ops != NULL) {
     200             :                 /*
     201             :                  * Set custom_ops the same as epoll,
     202             :                  * except re-init using std_event_context_init()
     203             :                  * and use std_event_loop_once() to add the
     204             :                  * ability to fallback to a poll backend on
     205             :                  * epoll runtime error.
     206             :                  */
     207    83086475 :                 *glue->glue_ops = *glue->epoll_ops;
     208    83086475 :                 glue->glue_ops->context_init = std_event_context_init;
     209    83086475 :                 glue->glue_ops->loop_once = std_event_loop_once;
     210    83086475 :                 glue->glue_ops->loop_wait = std_event_loop_wait;
     211             : 
     212    83086475 :                 ret = glue->epoll_ops->context_init(ev);
     213    83086475 :                 if (ret == -1) {
     214           0 :                         goto fallback;
     215             :                 }
     216             : #ifdef HAVE_EPOLL
     217    83086475 :                 tevent_epoll_set_panic_fallback(ev, std_fallback_to_poll);
     218             : #endif
     219             : 
     220    83086475 :                 return ret;
     221             :         }
     222             : 
     223           2 : fallback:
     224           2 :         glue->epoll_ops = NULL;
     225             : 
     226             :         /*
     227             :          * Set custom_ops the same as poll.
     228             :          */
     229           2 :         *glue->glue_ops = *glue->poll_ops;
     230           2 :         glue->glue_ops->context_init = std_event_context_init;
     231             : 
     232           2 :         return glue->poll_ops->context_init(ev);
     233             : }
     234             : 
     235       76842 : _PRIVATE_ bool tevent_standard_init(void)
     236             : {
     237       76842 :         return tevent_register_backend("standard", &std_event_ops);
     238             : }