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