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

   1 /* $OpenLDAP$ */
   2 /* This work is part of OpenLDAP Software <http://www.openldap.org/>.
   3  *
   4  * Copyright 1998-2005 The OpenLDAP Foundation.
   5  * All rights reserved.
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted only as authorized by the OpenLDAP
   9  * Public License.
  10  *
  11  * A copy of this license is available in file LICENSE in the
  12  * top-level directory of the distribution or, alternatively, at
  13  * <http://www.OpenLDAP.org/license.html>.
  14  */
  15
  16 #include "portable.h"
  17
  18 #include <stdio.h>
  19
  20 #include <ac/stdarg.h>
  21 #include <ac/stdlib.h>
  22 #include <ac/string.h>
  23 #include <ac/time.h>
  24 #include <ac/errno.h>
  25
  26 #include "ldap-int.h"
  27 #include "ldap_pvt_thread.h" /* Get the thread interface */
  28 #include "ldap_queue.h"
  29 #define LDAP_THREAD_POOL_IMPLEMENTATION
  30 #include "ldap_thr_debug.h"  /* May rename symbols defined below */
  31
  32 #ifndef LDAP_THREAD_HAVE_TPOOL
  33
  34 typedef enum ldap_int_thread_pool_state_e {
  35         LDAP_INT_THREAD_POOL_RUNNING,
  36         LDAP_INT_THREAD_POOL_FINISHING,
  37         LDAP_INT_THREAD_POOL_STOPPING,
  38         LDAP_INT_THREAD_POOL_PAUSING
  39 } ldap_int_thread_pool_state_t;
  40
  41 typedef struct ldap_int_thread_key_s {
  42         void *ltk_key;
  43         void *ltk_data;
  44         ldap_pvt_thread_pool_keyfree_t *ltk_free;
  45 } ldap_int_thread_key_t;
  46
  47 /* Max number of thread-specific keys we store per thread.
  48  * We don't expect to use many...
  49  */
  50 #define MAXKEYS 32
  51 #define LDAP_MAXTHR     1024    /* must be a power of 2 */
  52
  53 static ldap_pvt_thread_t tid_zero;
  54
  55 static struct {
  56         ldap_pvt_thread_t id;
  57         ldap_int_thread_key_t *ctx;
  58 } thread_keys[LDAP_MAXTHR];
  59
  60
  61 typedef struct ldap_int_thread_ctx_s {
  62         union {
  63         LDAP_STAILQ_ENTRY(ldap_int_thread_ctx_s) q;
  64         LDAP_SLIST_ENTRY(ldap_int_thread_ctx_s) l;
  65         LDAP_SLIST_ENTRY(ldap_int_thread_ctx_s) al;
  66         } ltc_next;
  67         ldap_pvt_thread_start_t *ltc_start_routine;
  68         void *ltc_arg;
  69 } ldap_int_thread_ctx_t;
  70
  71 struct ldap_int_thread_pool_s {
  72         LDAP_STAILQ_ENTRY(ldap_int_thread_pool_s) ltp_next;
  73         ldap_pvt_thread_mutex_t ltp_mutex;
  74         ldap_pvt_thread_cond_t ltp_cond;
  75         ldap_pvt_thread_cond_t ltp_pcond;
  76         LDAP_STAILQ_HEAD(tcq, ldap_int_thread_ctx_s) ltp_pending_list;
  77         LDAP_SLIST_HEAD(tcl, ldap_int_thread_ctx_s) ltp_free_list;
  78         LDAP_SLIST_HEAD(tclq, ldap_int_thread_ctx_s) ltp_active_list;
  79         ldap_int_thread_pool_state_t ltp_state;
  80         long ltp_max_count;
  81         long ltp_max_pending;
  82         long ltp_pending_count;
  83         long ltp_active_count;
  84         long ltp_open_count;
  85         long ltp_starting;
  86 };
  87
  88 static LDAP_STAILQ_HEAD(tpq, ldap_int_thread_pool_s)
  89         ldap_int_thread_pool_list =
  90         LDAP_STAILQ_HEAD_INITIALIZER(ldap_int_thread_pool_list);
  91
  92 static ldap_pvt_thread_mutex_t ldap_pvt_thread_pool_mutex;
  93
  94 static void *ldap_int_thread_pool_wrapper( void *pool );
  95
  96 static ldap_pvt_thread_t ldap_int_main_tid;
  97
  98 static ldap_int_thread_key_t ldap_int_main_thrctx[LDAP_MAXTHR];
  99
 100 int
 101 ldap_int_thread_pool_startup ( void )
 102 {
 103         ldap_int_main_tid = ldap_pvt_thread_self();
 104
 105         return ldap_pvt_thread_mutex_init(&ldap_pvt_thread_pool_mutex);
 106 }
 107
 108 int
 109 ldap_int_thread_pool_shutdown ( void )
 110 {
 111         struct ldap_int_thread_pool_s *pool;
 112
 113         while ((pool = LDAP_STAILQ_FIRST(&ldap_int_thread_pool_list)) != NULL) {
 114                 LDAP_STAILQ_REMOVE_HEAD(&ldap_int_thread_pool_list, ltp_next);
 115                 (ldap_pvt_thread_pool_destroy)(&pool, 0); /* ignore thr_debug macro */
 116         }
 117         ldap_pvt_thread_mutex_destroy(&ldap_pvt_thread_pool_mutex);
 118         return(0);
 119 }
 120
 121 typedef struct ldap_lazy_sem_t {
 122         ldap_pvt_thread_mutex_t ls_mutex;
 123         ldap_pvt_thread_cond_t  ls_cond;
 124         int ls_sem_value;
 125         /*
 126          * when more than ls_lazy_count number of resources
 127          * becmoes available, the thread wating for the resources will
 128          * be waken up in order to prevent frequent blocking/waking-up
 129          */
 130         unsigned int ls_lazy_count;
 131         /*
 132          * only one thread(listener) will wait on this semaphore
 133          * using a flag instead of a list
 134          */
 135         int ls_wait;
 136 } ldap_lazy_sem_t;
 137
 138 ldap_lazy_sem_t* thread_pool_sem = NULL;
 139
 140 int
 141 ldap_lazy_sem_init( unsigned int value, unsigned int lazyness )
 142 {
 143         thread_pool_sem = (ldap_lazy_sem_t*) LDAP_CALLOC(1,
 144                 sizeof( ldap_lazy_sem_t ));
 145
 146         if( thread_pool_sem == NULL ) return -1;
 147
 148         ldap_pvt_thread_mutex_init( &thread_pool_sem->ls_mutex );
 149         ldap_pvt_thread_cond_init( &thread_pool_sem->ls_cond );
 150         thread_pool_sem->ls_sem_value = value;
 151         thread_pool_sem->ls_lazy_count = lazyness;
 152         thread_pool_sem->ls_wait = 0;
 153
 154         return 0;
 155 }
 156
 157 /* FIXME: move to some approprite header */
 158 int ldap_lazy_sem_dec( ldap_lazy_sem_t* ls );
 159 int ldap_lazy_sem_wait ( ldap_lazy_sem_t* ls );
 160
 161 /*
 162  * ldap_lazy_sem_wait is used if a caller is blockable(listener).
 163  * Otherwise use ldap_lazy_sem_dec (worker)
 164  */
 165 int
 166 ldap_lazy_sem_op_submit( ldap_lazy_sem_t* ls )
 167 {
 168         if ( ls == NULL ) return -1;
 169
 170         /* only worker thread has its thread ctx */
 171         if ( ldap_pvt_thread_pool_context() ) {
 172                 /* worker thread */
 173                 return ldap_lazy_sem_dec( ls );
 174         } else {
 175                 /* listener */
 176                 return ldap_lazy_sem_wait( ls );
 177         }
 178 }
 179
 180 /*
 181  * test if given semaphore's count is zero.
 182  * If 0, the caller is blocked
 183  * If not, the count is decremented.
 184  */
 185 int
 186 ldap_lazy_sem_wait ( ldap_lazy_sem_t* ls )
 187 {
 188         ldap_pvt_thread_mutex_lock( &ls->ls_mutex );
 189
 190 lazy_sem_retry:
 191         if ( ls->ls_sem_value <= 0 ) {
 192                 /* no more avaliable resources */
 193                 ls->ls_wait = 1;
 194                 ldap_pvt_thread_cond_wait( &ls->ls_cond, &ls->ls_mutex );
 195                 goto lazy_sem_retry;
 196         } else {
 197                 /* avaliable resources */
 198                 ls->ls_sem_value--;
 199         }
 200
 201         ldap_pvt_thread_mutex_unlock( &ls->ls_mutex );
 202
 203         return 0;
 204 }
 205
 206 /*
 207  * decrement the count without blocking
 208  * even when the count becomes less than or equal to 0
 209  */
 210 int
 211 ldap_lazy_sem_dec( ldap_lazy_sem_t* ls )
 212 {
 213         ldap_pvt_thread_mutex_lock( &ls->ls_mutex );
 214
 215         ls->ls_sem_value--;
 216
 217         ldap_pvt_thread_mutex_unlock( &ls->ls_mutex );
 218
 219         return 0;
 220 }
 221
 222 /*
 223  * Increment the count by one and test if it is greater or
 224  * equal to lazyness. If it is, wake up a blocked thread.
 225  */
 226 int
 227 ldap_lazy_sem_post( ldap_lazy_sem_t* ls )
 228 {
 229         if( ls == NULL ) return (-1);
 230
 231         ldap_pvt_thread_mutex_lock( &ls->ls_mutex );
 232
 233         ls->ls_sem_value++;
 234         if ( ls->ls_wait ) {
 235                 if ( ls->ls_sem_value >= ls->ls_lazy_count ) {
 236                         ls->ls_wait = 0;
 237                         ldap_pvt_thread_cond_signal( &ls->ls_cond );
 238                 }
 239         }
 240
 241         ldap_pvt_thread_mutex_unlock( &ls->ls_mutex );
 242
 243         return 0;
 244 }
 245
 246 int
 247 ldap_pvt_thread_pool_init (
 248         ldap_pvt_thread_pool_t *tpool,
 249         int max_threads,
 250         int max_pending )
 251 {
 252         ldap_pvt_thread_pool_t pool;
 253         int rc;
 254
 255         *tpool = NULL;
 256         pool = (ldap_pvt_thread_pool_t) LDAP_CALLOC(1,
 257                 sizeof(struct ldap_int_thread_pool_s));
 258
 259         if (pool == NULL) return(-1);
 260
 261         rc = ldap_pvt_thread_mutex_init(&pool->ltp_mutex);
 262         if (rc != 0)
 263                 return(rc);
 264         rc = ldap_pvt_thread_cond_init(&pool->ltp_cond);
 265         if (rc != 0)
 266                 return(rc);
 267         rc = ldap_pvt_thread_cond_init(&pool->ltp_pcond);
 268         if (rc != 0)
 269                 return(rc);
 270         pool->ltp_state = LDAP_INT_THREAD_POOL_RUNNING;
 271         pool->ltp_max_count = max_threads;
 272         pool->ltp_max_pending = max_pending;
 273         LDAP_STAILQ_INIT(&pool->ltp_pending_list);
 274         LDAP_SLIST_INIT(&pool->ltp_free_list);
 275         LDAP_SLIST_INIT(&pool->ltp_active_list);
 276         ldap_pvt_thread_mutex_lock(&ldap_pvt_thread_pool_mutex);
 277         LDAP_STAILQ_INSERT_TAIL(&ldap_int_thread_pool_list, pool, ltp_next);
 278         ldap_pvt_thread_mutex_unlock(&ldap_pvt_thread_pool_mutex);
 279
 280 #if 0
 281         /* THIS WILL NOT WORK on some systems.  If the process
 282          * forks after starting a thread, there is no guarantee
 283          * that the thread will survive the fork.  For example,
 284          * slapd forks in order to daemonize, and does so after
 285          * calling ldap_pvt_thread_pool_init.  On some systems,
 286          * this initial thread does not run in the child process,
 287          * but ltp_open_count == 1, so two things happen:
 288          * 1) the first client connection fails, and 2) when
 289          * slapd is kill'ed, it never terminates since it waits
 290          * for all worker threads to exit. */
 291
 292         /* start up one thread, just so there is one. no need to
 293          * lock the mutex right now, since no threads are running.
 294          */
 295         pool->ltp_open_count++;
 296
 297         ldap_pvt_thread_t thr;
 298         rc = ldap_pvt_thread_create( &thr, 1, ldap_int_thread_pool_wrapper, pool );
 299
 300         if( rc != 0) {
 301                 /* couldn't start one?  then don't start any */
 302                 ldap_pvt_thread_mutex_lock(&ldap_pvt_thread_pool_mutex);
 303                 LDAP_STAILQ_REMOVE(ldap_int_thread_pool_list, pool,
 304                         ldap_int_thread_pool_s, ltp_next);
 305                 ldap_pvt_thread_mutex_unlock(&ldap_pvt_thread_pool_mutex);
 306                 ldap_pvt_thread_cond_destroy(&pool->ltp_pcond);
 307                 ldap_pvt_thread_cond_destroy(&pool->ltp_cond);
 308                 ldap_pvt_thread_mutex_destroy(&pool->ltp_mutex);
 309                 LDAP_FREE(pool);
 310                 return(-1);
 311         }
 312 #endif
 313
 314         *tpool = pool;
 315         return(0);
 316 }
 317
 318 #define TID_HASH(tid, hash) do { unsigned i; \
 319         unsigned char *ptr = (unsigned char *)&(tid); \
 320         for (i=0, hash=0; i<sizeof(tid); i++) hash += ptr[i]; } while(0)
 321
 322 int
 323 ldap_pvt_thread_pool_submit (
 324         ldap_pvt_thread_pool_t *tpool,
 325         ldap_pvt_thread_start_t *start_routine, void *arg )
 326 {
 327         struct ldap_int_thread_pool_s *pool;
 328         ldap_int_thread_ctx_t *ctx;
 329         int need_thread = 0;
 330         ldap_pvt_thread_t thr;
 331
 332         if (tpool == NULL)
 333                 return(-1);
 334
 335         pool = *tpool;
 336
 337         if (pool == NULL)
 338                 return(-1);
 339
 340         ldap_pvt_thread_mutex_lock(&pool->ltp_mutex);
 341         if ((pool->ltp_state != LDAP_INT_THREAD_POOL_RUNNING &&
 342                 pool->ltp_state != LDAP_INT_THREAD_POOL_PAUSING)
 343                 || (pool->ltp_max_pending > 0
 344                         && pool->ltp_pending_count >= pool->ltp_max_pending))
 345         {
 346                 ldap_pvt_thread_mutex_unlock(&pool->ltp_mutex);
 347                 return(-1);
 348         }
 349         ctx = LDAP_SLIST_FIRST(&pool->ltp_free_list);
 350         if (ctx) {
 351                 LDAP_SLIST_REMOVE_HEAD(&pool->ltp_free_list, ltc_next.l);
 352         } else {
 353                 ctx = (ldap_int_thread_ctx_t *) LDAP_MALLOC(
 354                         sizeof(ldap_int_thread_ctx_t));
 355                 if (ctx == NULL) {
 356                         ldap_pvt_thread_mutex_unlock(&pool->ltp_mutex);
 357                         return(-1);
 358                 }
 359         }
 360
 361         ctx->ltc_start_routine = start_routine;
 362         ctx->ltc_arg = arg;
 363
 364         pool->ltp_pending_count++;
 365         LDAP_STAILQ_INSERT_TAIL(&pool->ltp_pending_list, ctx, ltc_next.q);
 366         if (pool->ltp_state == LDAP_INT_THREAD_POOL_PAUSING) {
 367                 ldap_pvt_thread_mutex_unlock(&pool->ltp_mutex);
 368                 return(0);
 369         }
 370         ldap_pvt_thread_cond_signal(&pool->ltp_cond);
 371         if (pool->ltp_max_count <= 0
 372                         || pool->ltp_open_count < pool->ltp_max_count)
 373         {
 374                 pool->ltp_open_count++;
 375                 pool->ltp_starting++;
 376                 need_thread = 1;
 377         }
 378         ldap_pvt_thread_mutex_unlock(&pool->ltp_mutex);
 379
 380 #ifdef LDAP_PVT_THREAD_POOL_SEM_LOAD_CONTROL
 381         ldap_lazy_sem_op_submit( thread_pool_sem );
 382 #endif
 383
 384         if (need_thread) {
 385                 int rc;
 386
 387                 ldap_pvt_thread_mutex_lock(&pool->ltp_mutex);
 388
 389                 rc = ldap_pvt_thread_create( &thr, 1,
 390                         ldap_int_thread_pool_wrapper, pool );
 391                 if (rc == 0) {
 392                         int hash;
 393                         pool->ltp_starting--;
 394
 395                         /* assign this thread ID to a key slot; start
 396                          * at the thread ID itself (mod LDAP_MAXTHR) and
 397                          * look for an empty slot.
 398                          */
 399                         TID_HASH(thr, hash);
 400                         for (rc = hash & (LDAP_MAXTHR-1);
 401                                 !ldap_pvt_thread_equal(thread_keys[rc].id, tid_zero);
 402                                 rc = (rc+1) & (LDAP_MAXTHR-1));
 403                         thread_keys[rc].id = thr;
 404                 } else {
 405                         /* couldn't create thread.  back out of
 406                          * ltp_open_count and check for even worse things.
 407                          */
 408                         pool->ltp_open_count--;
 409                         pool->ltp_starting--;
 410                         if (pool->ltp_open_count == 0) {
 411                                 /* no open threads at all?!?
 412                                  */
 413                                 ldap_int_thread_ctx_t *ptr;
 414                                 LDAP_STAILQ_FOREACH(ptr, &pool->ltp_pending_list, ltc_next.q)
 415                                         if (ptr == ctx) break;
 416                                 if (ptr == ctx) {
 417                                         /* no open threads, context not handled, so
 418                                          * back out of ltp_pending_count, free the context,
 419                                          * report the error.
 420                                          */
 421                                         LDAP_STAILQ_REMOVE(&pool->ltp_pending_list, ctx,
 422                                                 ldap_int_thread_ctx_s, ltc_next.q);
 423                                         pool->ltp_pending_count++;
 424                                         ldap_pvt_thread_mutex_unlock(&pool->ltp_mutex);
 425                                         LDAP_FREE(ctx);
 426                                         return(-1);
 427                                 }
 428                         }
 429                         /* there is another open thread, so this
 430                          * context will be handled eventually.
 431                          * continue on and signal that the context
 432                          * is waiting.
 433                          */
 434                 }
 435                 ldap_pvt_thread_mutex_unlock(&pool->ltp_mutex);
 436         }
 437
 438         return(0);
 439 }
 440
 441 int
 442 ldap_pvt_thread_pool_maxthreads ( ldap_pvt_thread_pool_t *tpool, int max_threads )
 443 {
 444         struct ldap_int_thread_pool_s *pool;
 445
 446         if (tpool == NULL)
 447                 return(-1);
 448
 449         pool = *tpool;
 450
 451         if (pool == NULL)
 452                 return(-1);
 453
 454         ldap_pvt_thread_mutex_lock(&pool->ltp_mutex);
 455         pool->ltp_max_count = max_threads;
 456         ldap_pvt_thread_mutex_unlock(&pool->ltp_mutex);
 457         return(0);
 458 }
 459
 460 int
 461 ldap_pvt_thread_pool_backload ( ldap_pvt_thread_pool_t *tpool )
 462 {
 463         struct ldap_int_thread_pool_s *pool;
 464         int count;
 465
 466         if (tpool == NULL)
 467                 return(-1);
 468
 469         pool = *tpool;
 470
 471         if (pool == NULL)
 472                 return(0);
 473
 474         ldap_pvt_thread_mutex_lock(&pool->ltp_mutex);
 475         count = pool->ltp_pending_count + pool->ltp_active_count;
 476         ldap_pvt_thread_mutex_unlock(&pool->ltp_mutex);
 477         return(count);
 478 }
 479
 480 int
 481 ldap_pvt_thread_pool_destroy ( ldap_pvt_thread_pool_t *tpool, int run_pending )
 482 {
 483         struct ldap_int_thread_pool_s *pool, *pptr;
 484         long waiting;
 485         ldap_int_thread_ctx_t *ctx;
 486
 487         if (tpool == NULL)
 488                 return(-1);
 489
 490         pool = *tpool;
 491
 492         if (pool == NULL) return(-1);
 493
 494         ldap_pvt_thread_mutex_lock(&ldap_pvt_thread_pool_mutex);
 495         LDAP_STAILQ_FOREACH(pptr, &ldap_int_thread_pool_list, ltp_next)
 496                 if (pptr == pool) break;
 497         if (pptr == pool)
 498                 LDAP_STAILQ_REMOVE(&ldap_int_thread_pool_list, pool,
 499                         ldap_int_thread_pool_s, ltp_next);
 500         ldap_pvt_thread_mutex_unlock(&ldap_pvt_thread_pool_mutex);
 501
 502         if (pool != pptr) return(-1);
 503
 504         ldap_pvt_thread_mutex_lock(&pool->ltp_mutex);
 505         pool->ltp_state = run_pending
 506                 ? LDAP_INT_THREAD_POOL_FINISHING
 507                 : LDAP_INT_THREAD_POOL_STOPPING;
 508
 509         ldap_pvt_thread_cond_broadcast(&pool->ltp_cond);
 510         ldap_pvt_thread_mutex_unlock(&pool->ltp_mutex);
 511
 512         do {
 513                 ldap_pvt_thread_yield();
 514                 ldap_pvt_thread_mutex_lock(&pool->ltp_mutex);
 515                 waiting = pool->ltp_open_count;
 516                 ldap_pvt_thread_mutex_unlock(&pool->ltp_mutex);
 517         } while (waiting > 0);
 518
 519         while ((ctx = LDAP_STAILQ_FIRST(&pool->ltp_pending_list)) != NULL)
 520         {
 521                 LDAP_STAILQ_REMOVE_HEAD(&pool->ltp_pending_list, ltc_next.q);
 522                 LDAP_FREE(ctx);
 523         }
 524
 525         while ((ctx = LDAP_SLIST_FIRST(&pool->ltp_free_list)) != NULL)
 526         {
 527                 LDAP_SLIST_REMOVE_HEAD(&pool->ltp_free_list, ltc_next.l);
 528                 LDAP_FREE(ctx);
 529         }
 530
 531         ldap_pvt_thread_cond_destroy(&pool->ltp_pcond);
 532         ldap_pvt_thread_cond_destroy(&pool->ltp_cond);
 533         ldap_pvt_thread_mutex_destroy(&pool->ltp_mutex);
 534         LDAP_FREE(pool);
 535 #ifdef LDAP_PVT_THREAD_POOL_SEM_LOAD_CONTROL
 536         if ( thread_pool_sem ) {
 537                 LDAP_FREE( thread_pool_sem );
 538         }
 539 #endif
 540         return(0);
 541 }
 542
 543 static void *
 544 ldap_int_thread_pool_wrapper (
 545         void *xpool )
 546 {
 547         struct ldap_int_thread_pool_s *pool = xpool;
 548         ldap_int_thread_ctx_t *ctx;
 549         ldap_int_thread_key_t ltc_key[MAXKEYS];
 550         ldap_pvt_thread_t tid;
 551         int i, keyslot, hash;
 552
 553         if (pool == NULL)
 554                 return NULL;
 555
 556         for ( i=0; i<MAXKEYS; i++ ) {
 557                 ltc_key[i].ltk_key = NULL;
 558         }
 559
 560         tid = ldap_pvt_thread_self();
 561
 562         ldap_pvt_thread_mutex_lock(&pool->ltp_mutex);
 563
 564         /* store pointer to our keys */
 565         TID_HASH(tid, hash);
 566         for (i = hash & (LDAP_MAXTHR-1);
 567                                 !ldap_pvt_thread_equal(thread_keys[i].id, tid);
 568                                 i = (i+1) & (LDAP_MAXTHR-1));
 569         thread_keys[i].ctx = ltc_key;
 570         keyslot = i;
 571
 572         while (pool->ltp_state != LDAP_INT_THREAD_POOL_STOPPING) {
 573                 ctx = LDAP_STAILQ_FIRST(&pool->ltp_pending_list);
 574                 if (ctx) {
 575                         LDAP_STAILQ_REMOVE_HEAD(&pool->ltp_pending_list, ltc_next.q);
 576                 } else {
 577                         if (pool->ltp_state == LDAP_INT_THREAD_POOL_FINISHING)
 578                                 break;
 579                         if (pool->ltp_max_count > 0
 580                                 && pool->ltp_open_count > pool->ltp_max_count)
 581                         {
 582                                 /* too many threads running (can happen if the
 583                                  * maximum threads value is set during ongoing
 584                                  * operation using ldap_pvt_thread_pool_maxthreads)
 585                                  * so let this thread die.
 586                                  */
 587                                 break;
 588                         }
 589
 590                         /* we could check an idle timer here, and let the
 591                          * thread die if it has been inactive for a while.
 592                          * only die if there are other open threads (i.e.,
 593                          * always have at least one thread open).  the check
 594                          * should be like this:
 595                          *   if (pool->ltp_open_count > 1 && pool->ltp_starting == 0)
 596                          *       check timer, leave thread (break;)
 597                          */
 598
 599                         if (pool->ltp_state == LDAP_INT_THREAD_POOL_RUNNING
 600                                 || pool->ltp_state == LDAP_INT_THREAD_POOL_PAUSING)
 601                         {
 602                                 ldap_pvt_thread_cond_wait(&pool->ltp_cond, &pool->ltp_mutex);
 603                         }
 604
 605                         continue;
 606                 }
 607
 608                 pool->ltp_pending_count--;
 609
 610                 LDAP_SLIST_INSERT_HEAD(&pool->ltp_active_list, ctx, ltc_next.al);
 611                 pool->ltp_active_count++;
 612                 ldap_pvt_thread_mutex_unlock(&pool->ltp_mutex);
 613
 614                 ctx->ltc_start_routine(ltc_key, ctx->ltc_arg);
 615
 616 #ifdef LDAP_PVT_THREAD_POOL_SEM_LOAD_CONTROL
 617                 ldap_lazy_sem_post( thread_pool_sem );
 618 #endif
 619                 ldap_pvt_thread_mutex_lock(&pool->ltp_mutex);
 620                 LDAP_SLIST_REMOVE(&pool->ltp_active_list, ctx,
 621                         ldap_int_thread_ctx_s, ltc_next.al);
 622                 LDAP_SLIST_INSERT_HEAD(&pool->ltp_free_list, ctx, ltc_next.l);
 623                 pool->ltp_active_count--;
 624
 625                 if (pool->ltp_state == LDAP_INT_THREAD_POOL_PAUSING) {
 626                         if (pool->ltp_active_count < 2) {
 627                                 ldap_pvt_thread_cond_signal(&pool->ltp_pcond);
 628                         }
 629                         ldap_pvt_thread_cond_wait(&pool->ltp_cond, &pool->ltp_mutex);
 630                 }
 631                 ldap_pvt_thread_mutex_unlock(&pool->ltp_mutex);
 632
 633                 ldap_pvt_thread_yield();
 634
 635                 /* if we use an idle timer, here's
 636                  * a good place to update it
 637                  */
 638
 639                 ldap_pvt_thread_mutex_lock(&pool->ltp_mutex);
 640         }
 641
 642         for ( i=0; i<MAXKEYS && ltc_key[i].ltk_key; i++ ) {
 643                 if (ltc_key[i].ltk_free)
 644                         ltc_key[i].ltk_free(
 645                                 ltc_key[i].ltk_key,
 646                                 ltc_key[i].ltk_data );
 647         }
 648
 649         thread_keys[keyslot].ctx = NULL;
 650         thread_keys[keyslot].id = tid_zero;
 651
 652         pool->ltp_open_count--;
 653         ldap_pvt_thread_mutex_unlock(&pool->ltp_mutex);
 654
 655         ldap_pvt_thread_exit(NULL);
 656         return(NULL);
 657 }
 658
 659 int
 660 ldap_pvt_thread_pool_pause (
 661         ldap_pvt_thread_pool_t *tpool )
 662 {
 663         struct ldap_int_thread_pool_s *pool;
 664
 665         if (tpool == NULL)
 666                 return(-1);
 667
 668         pool = *tpool;
 669
 670         if (pool == NULL)
 671                 return(0);
 672
 673         ldap_pvt_thread_mutex_lock(&pool->ltp_mutex);
 674
 675         /* If someone else has already requested a pause, we have to wait */
 676         while (pool->ltp_state == LDAP_INT_THREAD_POOL_PAUSING) {
 677                 pool->ltp_pending_count++;
 678                 pool->ltp_active_count--;
 679                 ldap_pvt_thread_cond_wait(&pool->ltp_cond, &pool->ltp_mutex);
 680                 pool->ltp_pending_count--;
 681                 pool->ltp_active_count++;
 682         }
 683         /* Wait for everyone else to finish */
 684         pool->ltp_state = LDAP_INT_THREAD_POOL_PAUSING;
 685         while (pool->ltp_active_count > 1) {
 686                 ldap_pvt_thread_cond_wait(&pool->ltp_pcond, &pool->ltp_mutex);
 687         }
 688         ldap_pvt_thread_mutex_unlock(&pool->ltp_mutex);
 689         return(0);
 690 }
 691
 692 int
 693 ldap_pvt_thread_pool_resume (
 694         ldap_pvt_thread_pool_t *tpool )
 695 {
 696         struct ldap_int_thread_pool_s *pool;
 697
 698         if (tpool == NULL)
 699                 return(-1);
 700
 701         pool = *tpool;
 702
 703         if (pool == NULL)
 704                 return(0);
 705
 706         ldap_pvt_thread_mutex_lock(&pool->ltp_mutex);
 707
 708         pool->ltp_state = LDAP_INT_THREAD_POOL_RUNNING;
 709         ldap_pvt_thread_cond_broadcast(&pool->ltp_cond);
 710         ldap_pvt_thread_mutex_unlock(&pool->ltp_mutex);
 711         return(0);
 712 }
 713
 714 int ldap_pvt_thread_pool_getkey(
 715         void *xctx,
 716         void *key,
 717         void **data,
 718         ldap_pvt_thread_pool_keyfree_t **kfree )
 719 {
 720         ldap_int_thread_key_t *ctx = xctx;
 721         int i;
 722
 723         if ( !ctx || !data ) return EINVAL;
 724
 725         for ( i=0; i<MAXKEYS && ctx[i].ltk_key; i++ ) {
 726                 if ( ctx[i].ltk_key == key ) {
 727                         *data = ctx[i].ltk_data;
 728                         if ( kfree ) *kfree = ctx[i].ltk_free;
 729                         return 0;
 730                 }
 731         }
 732         return ENOENT;
 733 }
 734
 735 int ldap_pvt_thread_pool_setkey(
 736         void *xctx,
 737         void *key,
 738         void *data,
 739         ldap_pvt_thread_pool_keyfree_t *kfree )
 740 {
 741         ldap_int_thread_key_t *ctx = xctx;
 742         int i;
 743
 744         if ( !ctx || !key ) return EINVAL;
 745
 746         for ( i=0; i<MAXKEYS; i++ ) {
 747                 if ( !ctx[i].ltk_key || ctx[i].ltk_key == key ) {
 748                         ctx[i].ltk_key = key;
 749                         ctx[i].ltk_data = data;
 750                         ctx[i].ltk_free = kfree;
 751                         return 0;
 752                 }
 753         }
 754         return ENOMEM;
 755 }
 756
 757 /* Free all elements with this key, no matter which thread they're in.
 758  * May only be called while the pool is paused.
 759  */
 760 void ldap_pvt_thread_pool_purgekey( void *key )
 761 {
 762         int i, j;
 763         ldap_int_thread_key_t *ctx;
 764
 765         for ( i=0; i<LDAP_MAXTHR; i++ ) {
 766                 if ( thread_keys[i].ctx ) {
 767                         ctx = thread_keys[i].ctx;
 768                         for ( j=0; j<MAXKEYS; j++ ) {
 769                                 if ( ctx[j].ltk_key == key ) {
 770                                         if (ctx[j].ltk_free)
 771                                                 ctx[j].ltk_free( ctx[j].ltk_key, ctx[j].ltk_data );
 772                                         ctx[j].ltk_key = NULL;
 773                                         ctx[j].ltk_free = NULL;
 774                                         break;
 775                                 }
 776                         }
 777                 }
 778         }
 779 }
 780
 781 /*
 782  * This is necessary if the caller does not have access to the
 783  * thread context handle (for example, a slapd plugin calling
 784  * slapi_search_internal()). No doubt it is more efficient to
 785  * for the application to keep track of the thread context
 786  * handles itself.
 787  */
 788 void *ldap_pvt_thread_pool_context( )
 789 {
 790         ldap_pvt_thread_t tid;
 791         int i, hash;
 792
 793         tid = ldap_pvt_thread_self();
 794         if ( ldap_pvt_thread_equal( tid, ldap_int_main_tid ))
 795                 return ldap_int_main_thrctx;
 796
 797         TID_HASH( tid, hash );
 798         for (i = hash & (LDAP_MAXTHR-1);
 799                 !ldap_pvt_thread_equal(thread_keys[i].id, tid_zero) &&
 800                 !ldap_pvt_thread_equal(thread_keys[i].id, tid);
 801                 i = (i+1) & (LDAP_MAXTHR-1));
 802
 803         return thread_keys[i].ctx;
 804 }
 805
 806 void ldap_pvt_thread_pool_context_reset( void *vctx )
 807 {
 808         ldap_int_thread_key_t *ctx = vctx;
 809         int i;
 810
 811         for ( i=0; i<MAXKEYS && ctx[i].ltk_key; i++) {
 812                 if ( ctx[i].ltk_free )
 813                         ctx[i].ltk_free( ctx[i].ltk_key, ctx[i].ltk_data );
 814                 ctx[i].ltk_key = NULL;
 815         }
 816 }
 817 #endif /* LDAP_THREAD_HAVE_TPOOL */