git.sur5r.net Git - openldap/blob - libraries/libldap_r/tpool.c

   1 /* $OpenLDAP$ */
   2 /*
   3  * Copyright 1998-2000 The OpenLDAP Foundation, Redwood City, California, USA
   4  * All rights reserved.
   5  *
   6  * Redistribution and use in source and binary forms are permitted only
   7  * as authorized by the OpenLDAP Public License.  A copy of this
   8  * license is available at http://www.OpenLDAP.org/license.html or
   9  * in file LICENSE in the top-level directory of the distribution.
  10  */
  11
  12 #include "portable.h"
  13
  14 #include <stdio.h>
  15 #include <stdarg.h>
  16
  17 #include <ac/stdlib.h>
  18 #include <ac/string.h>
  19 #include <ac/time.h>
  20
  21 #include "ldap-int.h"
  22 #include "ldap_pvt_thread.h"
  23
  24 #ifndef LDAP_THREAD_HAVE_TPOOL
  25
  26 enum ldap_int_thread_pool_state {
  27         LDAP_INT_THREAD_POOL_RUNNING,
  28         LDAP_INT_THREAD_POOL_FINISHING,
  29         LDAP_INT_THREAD_POOL_STOPPING
  30 };
  31
  32 typedef struct ldap_int_thread_list_element_s {
  33         struct ldap_int_thread_list_element_s *next;
  34 } ldap_int_thread_list_element_t, *ldap_int_thread_list_t;
  35
  36 struct ldap_int_thread_pool_s {
  37         struct ldap_int_thread_pool_s *ltp_next;
  38         ldap_pvt_thread_mutex_t ltp_mutex;
  39         ldap_pvt_thread_cond_t ltp_cond;
  40         ldap_int_thread_list_t ltp_pending_list;
  41         long ltp_state;
  42         long ltp_max_count;
  43         long ltp_max_pending;
  44         long ltp_pending_count;
  45         long ltp_active_count;
  46         long ltp_open_count;
  47         long ltp_starting;
  48 };
  49
  50 typedef struct ldap_int_thread_ctx_s {
  51         struct ldap_int_thread_ctx_s *ltc_next;
  52         void *(*ltc_start_routine)( void *);
  53         void *ltc_arg;
  54 } ldap_int_thread_ctx_t;
  55
  56 static ldap_int_thread_list_t ldap_int_thread_pool_list = NULL;
  57 static ldap_pvt_thread_mutex_t ldap_pvt_thread_pool_mutex;
  58
  59 static void *ldap_int_thread_pool_wrapper(
  60         struct ldap_int_thread_pool_s *pool );
  61
  62 static void *ldap_int_thread_enlist( ldap_int_thread_list_t *list, void *elem );
  63 static void *ldap_int_thread_delist( ldap_int_thread_list_t *list, void *elem );
  64 static void *ldap_int_thread_onlist( ldap_int_thread_list_t *list, void *elem );
  65
  66 int
  67 ldap_int_thread_pool_startup ( void )
  68 {
  69         return ldap_pvt_thread_mutex_init(&ldap_pvt_thread_pool_mutex);
  70 }
  71
  72 int
  73 ldap_int_thread_pool_shutdown ( void )
  74 {
  75         while (ldap_int_thread_pool_list != NULL) {
  76                 struct ldap_int_thread_pool_s *pool =
  77                         (struct ldap_int_thread_pool_s *) ldap_int_thread_pool_list;
  78
  79                 ldap_pvt_thread_pool_destroy( &pool, 0);
  80         }
  81         ldap_pvt_thread_mutex_destroy(&ldap_pvt_thread_pool_mutex);
  82         return(0);
  83 }
  84
  85 int
  86 ldap_pvt_thread_pool_init (
  87         ldap_pvt_thread_pool_t *tpool,
  88         int max_threads,
  89         int max_pending )
  90 {
  91         ldap_pvt_thread_pool_t pool;
  92         int rc;
  93
  94         *tpool = NULL;
  95         pool = (ldap_pvt_thread_pool_t) LDAP_CALLOC(1,
  96                 sizeof(struct ldap_int_thread_pool_s));
  97
  98         if (pool == NULL) return(-1);
  99
 100         rc = ldap_pvt_thread_mutex_init(&pool->ltp_mutex);
 101         if (rc != 0)
 102                 return(rc);
 103         rc = ldap_pvt_thread_cond_init(&pool->ltp_cond);
 104         if (rc != 0)
 105                 return(rc);
 106         pool->ltp_state = LDAP_INT_THREAD_POOL_RUNNING;
 107         pool->ltp_max_count = max_threads;
 108         pool->ltp_max_pending = max_pending;
 109         ldap_pvt_thread_mutex_lock(&ldap_pvt_thread_pool_mutex);
 110         ldap_int_thread_enlist(&ldap_int_thread_pool_list, pool);
 111         ldap_pvt_thread_mutex_unlock(&ldap_pvt_thread_pool_mutex);
 112
 113 #if 0
 114         /* THIS WILL NOT WORK on some systems.  If the process
 115          * forks after starting a thread, there is no guarantee
 116          * that the thread will survive the fork.  For example,
 117          * slapd forks in order to daemonize, and does so after
 118          * calling ldap_pvt_thread_pool_init.  On some systems,
 119          * this initial thread does not run in the child process,
 120          * but ltp_open_count == 1, so two things happen:
 121          * 1) the first client connection fails, and 2) when
 122          * slapd is kill'ed, it never terminates since it waits
 123          * for all worker threads to exit.
 124
 125         /* start up one thread, just so there is one. no need to
 126          * lock the mutex right now, since no threads are running.
 127          */
 128         pool->ltp_open_count++;
 129
 130         ldap_pvt_thread_t thr;
 131         rc = ldap_pvt_thread_create( &thr, 1,
 132                 (void *) ldap_int_thread_pool_wrapper, pool );
 133
 134         if( rc != 0) {
 135                 /* couldn't start one?  then don't start any */
 136                 ldap_pvt_thread_mutex_lock(&ldap_pvt_thread_pool_mutex);
 137                 ldap_int_thread_delist(&ldap_int_thread_pool_list, pool);
 138                 ldap_pvt_thread_mutex_unlock(&ldap_pvt_thread_pool_mutex);
 139                 ldap_pvt_thread_cond_destroy(&pool->ltp_cond);
 140                 ldap_pvt_thread_mutex_destroy(&pool->ltp_mutex);
 141                 free(pool);
 142                 return(-1);
 143         }
 144 #endif
 145
 146         *tpool = pool;
 147         return(0);
 148 }
 149
 150 int
 151 ldap_pvt_thread_pool_submit (
 152         ldap_pvt_thread_pool_t *tpool,
 153         void *(*start_routine)( void * ), void *arg )
 154 {
 155         struct ldap_int_thread_pool_s *pool;
 156         ldap_int_thread_ctx_t *ctx;
 157         int need_thread = 0;
 158         ldap_pvt_thread_t thr;
 159
 160         if (tpool == NULL)
 161                 return(-1);
 162
 163         pool = *tpool;
 164
 165         if (pool == NULL)
 166                 return(-1);
 167
 168         ctx = (ldap_int_thread_ctx_t *) LDAP_CALLOC(1,
 169                 sizeof(ldap_int_thread_ctx_t));
 170
 171         if (ctx == NULL) return(-1);
 172
 173         ctx->ltc_start_routine = start_routine;
 174         ctx->ltc_arg = arg;
 175
 176         ldap_pvt_thread_mutex_lock(&pool->ltp_mutex);
 177         if (pool->ltp_state != LDAP_INT_THREAD_POOL_RUNNING
 178                 || (pool->ltp_max_pending > 0
 179                         && pool->ltp_pending_count >= pool->ltp_max_pending))
 180         {
 181                 ldap_pvt_thread_mutex_unlock(&pool->ltp_mutex);
 182                 free(ctx);
 183                 return(-1);
 184         }
 185         pool->ltp_pending_count++;
 186         ldap_int_thread_enlist(&pool->ltp_pending_list, ctx);
 187         ldap_pvt_thread_cond_signal(&pool->ltp_cond);
 188         if ((pool->ltp_open_count <= 0
 189                         || pool->ltp_pending_count > 1
 190                         || pool->ltp_open_count == pool->ltp_active_count)
 191                 && (pool->ltp_max_count <= 0
 192                         || pool->ltp_open_count < pool->ltp_max_count))
 193         {
 194                 pool->ltp_open_count++;
 195                 pool->ltp_starting++;
 196                 need_thread = 1;
 197         }
 198         ldap_pvt_thread_mutex_unlock(&pool->ltp_mutex);
 199
 200         if (need_thread) {
 201                 int rc = ldap_pvt_thread_create( &thr, 1,
 202                         (void *)ldap_int_thread_pool_wrapper, pool );
 203                 ldap_pvt_thread_mutex_lock(&pool->ltp_mutex);
 204                 if (rc == 0) {
 205                         pool->ltp_starting--;
 206                 } else {
 207                         /* couldn't create thread.  back out of
 208                          * ltp_open_count and check for even worse things.
 209                          */
 210                         pool->ltp_open_count--;
 211                         pool->ltp_starting--;
 212                         if (pool->ltp_open_count == 0) {
 213                                 /* no open threads at all?!?
 214                                  */
 215                                 if (ldap_int_thread_delist(&pool->ltp_pending_list, ctx)) {
 216                                         /* no open threads, context not handled, so
 217                                          * back out of ltp_pending_count, free the context,
 218                                          * report the error.
 219                                          */
 220                                         pool->ltp_pending_count++;
 221                                         ldap_pvt_thread_mutex_unlock(&pool->ltp_mutex);
 222                                         free(ctx);
 223                                         return(-1);
 224                                 }
 225                         }
 226                         /* there is another open thread, so this
 227                          * context will be handled eventually.
 228                          * continue on and signal that the context
 229                          * is waiting.
 230                          */
 231                 }
 232                 ldap_pvt_thread_mutex_unlock(&pool->ltp_mutex);
 233         }
 234
 235         return(0);
 236 }
 237
 238 int
 239 ldap_pvt_thread_pool_maxthreads ( ldap_pvt_thread_pool_t *tpool, int max_threads )
 240 {
 241         struct ldap_int_thread_pool_s *pool;
 242
 243         if (tpool == NULL)
 244                 return(-1);
 245
 246         pool = *tpool;
 247
 248         if (pool == NULL)
 249                 return(-1);
 250
 251         ldap_pvt_thread_mutex_lock(&pool->ltp_mutex);
 252         pool->ltp_max_count = max_threads;
 253         ldap_pvt_thread_mutex_unlock(&pool->ltp_mutex);
 254         return(0);
 255 }
 256
 257 int
 258 ldap_pvt_thread_pool_backload ( ldap_pvt_thread_pool_t *tpool )
 259 {
 260         struct ldap_int_thread_pool_s *pool;
 261         int count;
 262
 263         if (tpool == NULL)
 264                 return(-1);
 265
 266         pool = *tpool;
 267
 268         if (pool == NULL)
 269                 return(0);
 270
 271         ldap_pvt_thread_mutex_lock(&pool->ltp_mutex);
 272         count = pool->ltp_pending_count + pool->ltp_active_count;
 273         ldap_pvt_thread_mutex_unlock(&pool->ltp_mutex);
 274         return(count);
 275 }
 276
 277 int
 278 ldap_pvt_thread_pool_destroy ( ldap_pvt_thread_pool_t *tpool, int run_pending )
 279 {
 280         struct ldap_int_thread_pool_s *pool;
 281         long waiting;
 282         ldap_int_thread_ctx_t *ctx;
 283
 284         if (tpool == NULL)
 285                 return(-1);
 286
 287         pool = *tpool;
 288
 289         if (pool == NULL) return(-1);
 290
 291         ldap_pvt_thread_mutex_lock(&ldap_pvt_thread_pool_mutex);
 292         pool = ldap_int_thread_delist(&ldap_int_thread_pool_list, pool);
 293         ldap_pvt_thread_mutex_unlock(&ldap_pvt_thread_pool_mutex);
 294
 295         if (pool == NULL) return(-1);
 296
 297         ldap_pvt_thread_mutex_lock(&pool->ltp_mutex);
 298         pool->ltp_state = run_pending
 299                 ? LDAP_INT_THREAD_POOL_FINISHING
 300                 : LDAP_INT_THREAD_POOL_STOPPING;
 301         waiting = pool->ltp_open_count;
 302
 303         /* broadcast could be used here, but only after
 304          * it is fixed in the NT thread implementation
 305          */
 306         while (--waiting >= 0) {
 307                 ldap_pvt_thread_cond_signal(&pool->ltp_cond);
 308         }
 309         ldap_pvt_thread_mutex_unlock(&pool->ltp_mutex);
 310
 311         do {
 312                 ldap_pvt_thread_yield();
 313                 ldap_pvt_thread_mutex_lock(&pool->ltp_mutex);
 314                 waiting = pool->ltp_open_count;
 315                 ldap_pvt_thread_mutex_unlock(&pool->ltp_mutex);
 316         } while (waiting > 0);
 317
 318         while (ctx = (ldap_int_thread_ctx_t *)ldap_int_thread_delist(
 319                 &pool->ltp_pending_list, NULL))
 320         {
 321                 free(ctx);
 322         }
 323
 324         ldap_pvt_thread_cond_destroy(&pool->ltp_cond);
 325         ldap_pvt_thread_mutex_destroy(&pool->ltp_mutex);
 326         free(pool);
 327         return(0);
 328 }
 329
 330 static void *
 331 ldap_int_thread_pool_wrapper (
 332         struct ldap_int_thread_pool_s *pool )
 333 {
 334         ldap_int_thread_ctx_t *ctx;
 335
 336         if (pool == NULL)
 337                 return NULL;
 338
 339         ldap_pvt_thread_mutex_lock(&pool->ltp_mutex);
 340
 341         while (pool->ltp_state != LDAP_INT_THREAD_POOL_STOPPING) {
 342
 343                 ctx = ldap_int_thread_delist(&pool->ltp_pending_list, NULL);
 344                 if (ctx == NULL) {
 345                         if (pool->ltp_state == LDAP_INT_THREAD_POOL_FINISHING)
 346                                 break;
 347                         if (pool->ltp_max_count > 0
 348                                 && pool->ltp_open_count > pool->ltp_max_count)
 349                         {
 350                                 /* too many threads running (can happen if the
 351                                  * maximum threads value is set during ongoing
 352                                  * operation using ldap_pvt_thread_pool_maxthreads)
 353                                  * so let this thread die.
 354                                  */
 355                                 break;
 356                         }
 357
 358                         /* we could check an idle timer here, and let the
 359                          * thread die if it has been inactive for a while.
 360                          * only die if there are other open threads (i.e.,
 361                          * always have at least one thread open).  the check
 362                          * should be like this:
 363                          *   if (pool->ltp_open_count > 1 && pool->ltp_starting == 0)
 364                          *       check timer, leave thread (break;)
 365                          */
 366
 367                         if (pool->ltp_state == LDAP_INT_THREAD_POOL_RUNNING)
 368                                 ldap_pvt_thread_cond_wait(&pool->ltp_cond, &pool->ltp_mutex);
 369
 370                         continue;
 371                 }
 372
 373                 pool->ltp_pending_count--;
 374                 pool->ltp_active_count++;
 375                 ldap_pvt_thread_mutex_unlock(&pool->ltp_mutex);
 376
 377                 (ctx->ltc_start_routine)(ctx->ltc_arg);
 378                 free(ctx);
 379                 ldap_pvt_thread_yield();
 380
 381                 /* if we use an idle timer, here's
 382                  * a good place to update it
 383                  */
 384
 385                 ldap_pvt_thread_mutex_lock(&pool->ltp_mutex);
 386                 pool->ltp_active_count--;
 387         }
 388
 389         pool->ltp_open_count--;
 390         ldap_pvt_thread_mutex_unlock(&pool->ltp_mutex);
 391
 392         ldap_pvt_thread_exit(NULL);
 393         return(NULL);
 394 }
 395
 396 static void *
 397 ldap_int_thread_enlist( ldap_int_thread_list_t *list, void *elem )
 398 {
 399         ldap_int_thread_list_element_t *prev;
 400
 401         if (elem == NULL) return(NULL);
 402
 403         ((ldap_int_thread_list_element_t *)elem)->next = NULL;
 404         if (*list == NULL) {
 405                 *list = elem;
 406                 return(elem);
 407         }
 408
 409         for (prev = *list ; prev->next != NULL; prev = prev->next) ;
 410         prev->next = elem;
 411         return(elem);
 412 }
 413
 414 static void *
 415 ldap_int_thread_delist( ldap_int_thread_list_t *list, void *elem )
 416 {
 417         ldap_int_thread_list_element_t *prev;
 418
 419         if (*list == NULL) return(NULL);
 420
 421         if (elem == NULL) elem = *list;
 422
 423         if (*list == elem) {
 424                 *list = ((ldap_int_thread_list_element_t *)elem)->next;
 425                 return(elem);
 426         }
 427
 428         for (prev = *list ; prev->next != NULL; prev = prev->next) {
 429                 if (prev->next == elem) {
 430                         prev->next = ((ldap_int_thread_list_element_t *)elem)->next;
 431                         return(elem);
 432                 }
 433         }
 434         return(NULL);
 435 }
 436
 437 static void *
 438 ldap_int_thread_onlist( ldap_int_thread_list_t *list, void *elem )
 439 {
 440         ldap_int_thread_list_element_t *prev;
 441
 442         if (elem == NULL || *list == NULL) return(NULL);
 443
 444         for (prev = *list ; prev != NULL; prev = prev->next) {
 445                 if (prev == elem)
 446                         return(elem);
 447         }
 448
 449         return(NULL);
 450 }
 451
 452 #endif /* LDAP_HAVE_THREAD_POOL */