lib/tevent/tevent_queue.c

   1 /*
   2    Unix SMB/CIFS implementation.
   3    Infrastructure for async requests
   4    Copyright (C) Volker Lendecke 2008
   5    Copyright (C) Stefan Metzmacher 2009
   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 #include "replace.h"
  26 #include "tevent.h"
  27 #include "tevent_internal.h"
  28 #include "tevent_util.h"
  29
  30 struct tevent_queue_entry {
  31         struct tevent_queue_entry *prev, *next;
  32         struct tevent_queue *queue;
  33
  34         bool triggered;
  35
  36         struct tevent_req *req;
  37         struct tevent_context *ev;
  38
  39         tevent_queue_trigger_fn_t trigger;
  40         void *private_data;
  41 };
  42
  43 struct tevent_queue {
  44         const char *name;
  45         const char *location;
  46
  47         bool running;
  48         struct tevent_immediate *immediate;
  49
  50         size_t length;
  51         struct tevent_queue_entry *list;
  52 };
  53
  54 static void tevent_queue_immediate_trigger(struct tevent_context *ev,
  55                                            struct tevent_immediate *im,
  56                                            void *private_data);
  57
  58 static int tevent_queue_entry_destructor(struct tevent_queue_entry *e)
  59 {
  60         struct tevent_queue *q = e->queue;
  61
  62         if (!q) {
  63                 return 0;
  64         }
  65
  66         DLIST_REMOVE(q->list, e);
  67         q->length--;
  68
  69         if (!q->running) {
  70                 return 0;
  71         }
  72
  73         if (!q->list) {
  74                 return 0;
  75         }
  76
  77         if (q->list->triggered) {
  78                 return 0;
  79         }
  80
  81         tevent_schedule_immediate(q->immediate,
  82                                   q->list->ev,
  83                                   tevent_queue_immediate_trigger,
  84                                   q);
  85
  86         return 0;
  87 }
  88
  89 static int tevent_queue_destructor(struct tevent_queue *q)
  90 {
  91         q->running = false;
  92
  93         while (q->list) {
  94                 struct tevent_queue_entry *e = q->list;
  95                 talloc_free(e);
  96         }
  97
  98         return 0;
  99 }
 100
 101 struct tevent_queue *_tevent_queue_create(TALLOC_CTX *mem_ctx,
 102                                           const char *name,
 103                                           const char *location)
 104 {
 105         struct tevent_queue *queue;
 106
 107         queue = talloc_zero(mem_ctx, struct tevent_queue);
 108         if (!queue) {
 109                 return NULL;
 110         }
 111
 112         queue->name = talloc_strdup(queue, name);
 113         if (!queue->name) {
 114                 talloc_free(queue);
 115                 return NULL;
 116         }
 117         queue->immediate = tevent_create_immediate(queue);
 118         if (!queue->immediate) {
 119                 talloc_free(queue);
 120                 return NULL;
 121         }
 122
 123         queue->location = location;
 124
 125         /* queue is running by default */
 126         queue->running = true;
 127
 128         talloc_set_destructor(queue, tevent_queue_destructor);
 129         return queue;
 130 }
 131
 132 static void tevent_queue_immediate_trigger(struct tevent_context *ev,
 133                                            struct tevent_immediate *im,
 134                                            void *private_data)
 135 {
 136         struct tevent_queue *q = talloc_get_type(private_data,
 137                                   struct tevent_queue);
 138
 139         if (!q->running) {
 140                 return;
 141         }
 142
 143         if (!q->list) {
 144                 return;
 145         }
 146
 147         q->list->triggered = true;
 148         q->list->trigger(q->list->req, q->list->private_data);
 149 }
 150
 151 static struct tevent_queue_entry *tevent_queue_add_internal(
 152                                         struct tevent_queue *queue,
 153                                         struct tevent_context *ev,
 154                                         struct tevent_req *req,
 155                                         tevent_queue_trigger_fn_t trigger,
 156                                         void *private_data,
 157                                         bool allow_direct)
 158 {
 159         struct tevent_queue_entry *e;
 160
 161         e = talloc_zero(req, struct tevent_queue_entry);
 162         if (e == NULL) {
 163                 return NULL;
 164         }
 165
 166         e->queue = queue;
 167         e->req = req;
 168         e->ev = ev;
 169         e->trigger = trigger;
 170         e->private_data = private_data;
 171
 172         /*
 173          * if there is no trigger, it is just a blocker
 174          */
 175         if (trigger == NULL) {
 176                 e->triggered = true;
 177         }
 178
 179         if (queue->length > 0) {
 180                 /*
 181                  * if there are already entries in the
 182                  * queue do not optimize.
 183                  */
 184                 allow_direct = false;
 185         }
 186
 187         if (req->async.fn != NULL) {
 188                 /*
 189                  * If the callers wants to optimize for the
 190                  * empty queue case, call the trigger only
 191                  * if there is no callback defined for the
 192                  * request yet.
 193                  */
 194                 allow_direct = false;
 195         }
 196
 197         DLIST_ADD_END(queue->list, e, struct tevent_queue_entry *);
 198         queue->length++;
 199         talloc_set_destructor(e, tevent_queue_entry_destructor);
 200
 201         if (!queue->running) {
 202                 return e;
 203         }
 204
 205         if (queue->list->triggered) {
 206                 return e;
 207         }
 208
 209         /*
 210          * If allowed we directly call the trigger
 211          * avoiding possible delays caused by
 212          * an immediate event.
 213          */
 214         if (allow_direct) {
 215                 queue->list->triggered = true;
 216                 queue->list->trigger(queue->list->req,
 217                                      queue->list->private_data);
 218                 return e;
 219         }
 220
 221         tevent_schedule_immediate(queue->immediate,
 222                                   queue->list->ev,
 223                                   tevent_queue_immediate_trigger,
 224                                   queue);
 225
 226         return e;
 227 }
 228
 229 bool tevent_queue_add(struct tevent_queue *queue,
 230                       struct tevent_context *ev,
 231                       struct tevent_req *req,
 232                       tevent_queue_trigger_fn_t trigger,
 233                       void *private_data)
 234 {
 235         struct tevent_queue_entry *e;
 236
 237         e = tevent_queue_add_internal(queue, ev, req,
 238                                       trigger, private_data, false);
 239         if (e == NULL) {
 240                 return false;
 241         }
 242
 243         return true;
 244 }
 245
 246 struct tevent_queue_entry *tevent_queue_add_entry(
 247                                         struct tevent_queue *queue,
 248                                         struct tevent_context *ev,
 249                                         struct tevent_req *req,
 250                                         tevent_queue_trigger_fn_t trigger,
 251                                         void *private_data)
 252 {
 253         return tevent_queue_add_internal(queue, ev, req,
 254                                          trigger, private_data, false);
 255 }
 256
 257 struct tevent_queue_entry *tevent_queue_add_optimize_empty(
 258                                         struct tevent_queue *queue,
 259                                         struct tevent_context *ev,
 260                                         struct tevent_req *req,
 261                                         tevent_queue_trigger_fn_t trigger,
 262                                         void *private_data)
 263 {
 264         return tevent_queue_add_internal(queue, ev, req,
 265                                          trigger, private_data, true);
 266 }
 267
 268 void tevent_queue_start(struct tevent_queue *queue)
 269 {
 270         if (queue->running) {
 271                 /* already started */
 272                 return;
 273         }
 274
 275         queue->running = true;
 276
 277         if (!queue->list) {
 278                 return;
 279         }
 280
 281         if (queue->list->triggered) {
 282                 return;
 283         }
 284
 285         tevent_schedule_immediate(queue->immediate,
 286                                   queue->list->ev,
 287                                   tevent_queue_immediate_trigger,
 288                                   queue);
 289 }
 290
 291 void tevent_queue_stop(struct tevent_queue *queue)
 292 {
 293         queue->running = false;
 294 }
 295
 296 size_t tevent_queue_length(struct tevent_queue *queue)
 297 {
 298         return queue->length;
 299 }
 300
 301 bool tevent_queue_running(struct tevent_queue *queue)
 302 {
 303         return queue->running;
 304 }