source3/lib/pthreadpool/pthreadpool.c

   1 /*
   2  * Unix SMB/CIFS implementation.
   3  * thread pool implementation
   4  * Copyright (C) Volker Lendecke 2009
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 3 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  18  */
  19
  20 #include "config.h"
  21 #include <errno.h>
  22 #include <stdio.h>
  23 #include <stdlib.h>
  24 #include <string.h>
  25 #include <pthread.h>
  26 #include <signal.h>
  27 #include <assert.h>
  28 #include <fcntl.h>
  29 #include "system/time.h"
  30 #include "system/filesys.h"
  31 #include "replace.h"
  32
  33 #include "pthreadpool.h"
  34 #include "lib/util/dlinklist.h"
  35
  36 struct pthreadpool_job {
  37         struct pthreadpool_job *next;
  38         int id;
  39         void (*fn)(void *private_data);
  40         void *private_data;
  41 };
  42
  43 struct pthreadpool {
  44         /*
  45          * List pthreadpools for fork safety
  46          */
  47         struct pthreadpool *prev, *next;
  48
  49         /*
  50          * Control access to this struct
  51          */
  52         pthread_mutex_t mutex;
  53
  54         /*
  55          * Threads waiting for work do so here
  56          */
  57         pthread_cond_t condvar;
  58
  59         /*
  60          * List of work jobs
  61          */
  62         struct pthreadpool_job *jobs, *last_job;
  63
  64         /*
  65          * pipe for signalling
  66          */
  67         int sig_pipe[2];
  68
  69         /*
  70          * indicator to worker threads that they should shut down
  71          */
  72         int shutdown;
  73
  74         /*
  75          * maximum number of threads
  76          */
  77         int max_threads;
  78
  79         /*
  80          * Number of threads
  81          */
  82         int num_threads;
  83
  84         /*
  85          * Number of idle threads
  86          */
  87         int num_idle;
  88
  89         /*
  90          * An array of threads that require joining.
  91          */
  92         int                     num_exited;
  93         pthread_t               *exited; /* We alloc more */
  94 };
  95
  96 static pthread_mutex_t pthreadpools_mutex = PTHREAD_MUTEX_INITIALIZER;
  97 static struct pthreadpool *pthreadpools = NULL;
  98 static pthread_once_t pthreadpool_atfork_initialized = PTHREAD_ONCE_INIT;
  99
 100 static void pthreadpool_prep_atfork(void);
 101
 102 /*
 103  * Initialize a thread pool
 104  */
 105
 106 int pthreadpool_init(unsigned max_threads, struct pthreadpool **presult)
 107 {
 108         struct pthreadpool *pool;
 109         int ret;
 110
 111         pool = (struct pthreadpool *)malloc(sizeof(struct pthreadpool));
 112         if (pool == NULL) {
 113                 return ENOMEM;
 114         }
 115
 116         ret = pipe(pool->sig_pipe);
 117         if (ret == -1) {
 118                 int err = errno;
 119                 free(pool);
 120                 return err;
 121         }
 122
 123         ret = pthread_mutex_init(&pool->mutex, NULL);
 124         if (ret != 0) {
 125                 close(pool->sig_pipe[0]);
 126                 close(pool->sig_pipe[1]);
 127                 free(pool);
 128                 return ret;
 129         }
 130
 131         ret = pthread_cond_init(&pool->condvar, NULL);
 132         if (ret != 0) {
 133                 pthread_mutex_destroy(&pool->mutex);
 134                 close(pool->sig_pipe[0]);
 135                 close(pool->sig_pipe[1]);
 136                 free(pool);
 137                 return ret;
 138         }
 139
 140         pool->shutdown = 0;
 141         pool->jobs = pool->last_job = NULL;
 142         pool->num_threads = 0;
 143         pool->num_exited = 0;
 144         pool->exited = NULL;
 145         pool->max_threads = max_threads;
 146         pool->num_idle = 0;
 147
 148         ret = pthread_mutex_lock(&pthreadpools_mutex);
 149         if (ret != 0) {
 150                 pthread_cond_destroy(&pool->condvar);
 151                 pthread_mutex_destroy(&pool->mutex);
 152                 close(pool->sig_pipe[0]);
 153                 close(pool->sig_pipe[1]);
 154                 free(pool);
 155                 return ret;
 156         }
 157         DLIST_ADD(pthreadpools, pool);
 158
 159         ret = pthread_mutex_unlock(&pthreadpools_mutex);
 160         assert(ret == 0);
 161
 162         pthread_once(&pthreadpool_atfork_initialized, pthreadpool_prep_atfork);
 163
 164         *presult = pool;
 165
 166         return 0;
 167 }
 168
 169 static void pthreadpool_prepare(void)
 170 {
 171         int ret;
 172         struct pthreadpool *pool;
 173
 174         ret = pthread_mutex_lock(&pthreadpools_mutex);
 175         assert(ret == 0);
 176
 177         pool = pthreadpools;
 178
 179         while (pool != NULL) {
 180                 ret = pthread_mutex_lock(&pool->mutex);
 181                 assert(ret == 0);
 182                 pool = pool->next;
 183         }
 184 }
 185
 186 static void pthreadpool_parent(void)
 187 {
 188         int ret;
 189         struct pthreadpool *pool;
 190
 191         pool = DLIST_TAIL(pthreadpools);
 192
 193         while (1) {
 194                 ret = pthread_mutex_unlock(&pool->mutex);
 195                 assert(ret == 0);
 196
 197                 if (pool == pthreadpools) {
 198                         break;
 199                 }
 200                 pool = pool->prev;
 201         }
 202
 203         ret = pthread_mutex_unlock(&pthreadpools_mutex);
 204         assert(ret == 0);
 205 }
 206
 207 static void pthreadpool_child(void)
 208 {
 209         int ret;
 210         struct pthreadpool *pool;
 211
 212         pool = DLIST_TAIL(pthreadpools);
 213
 214         while (1) {
 215                 close(pool->sig_pipe[0]);
 216                 close(pool->sig_pipe[1]);
 217
 218                 ret = pipe(pool->sig_pipe);
 219                 assert(ret == 0);
 220
 221                 pool->num_threads = 0;
 222
 223                 pool->num_exited = 0;
 224                 free(pool->exited);
 225                 pool->exited = NULL;
 226
 227                 pool->num_idle = 0;
 228
 229                 while (pool->jobs != NULL) {
 230                         struct pthreadpool_job *job;
 231                         job = pool->jobs;
 232                         pool->jobs = job->next;
 233                         free(job);
 234                 }
 235                 pool->last_job = NULL;
 236
 237                 ret = pthread_mutex_unlock(&pool->mutex);
 238                 assert(ret == 0);
 239
 240                 if (pool == pthreadpools) {
 241                         break;
 242                 }
 243                 pool = pool->prev;
 244         }
 245
 246         ret = pthread_mutex_unlock(&pthreadpools_mutex);
 247         assert(ret == 0);
 248 }
 249
 250 static void pthreadpool_prep_atfork(void)
 251 {
 252         pthread_atfork(pthreadpool_prepare, pthreadpool_parent,
 253                        pthreadpool_child);
 254 }
 255
 256 /*
 257  * Return the file descriptor which becomes readable when a job has
 258  * finished
 259  */
 260
 261 int pthreadpool_signal_fd(struct pthreadpool *pool)
 262 {
 263         return pool->sig_pipe[0];
 264 }
 265
 266 /*
 267  * Do a pthread_join() on all children that have exited, pool->mutex must be
 268  * locked
 269  */
 270 static void pthreadpool_join_children(struct pthreadpool *pool)
 271 {
 272         int i;
 273
 274         for (i=0; i<pool->num_exited; i++) {
 275                 pthread_join(pool->exited[i], NULL);
 276         }
 277         pool->num_exited = 0;
 278
 279         /*
 280          * Deliberately not free and NULL pool->exited. That will be
 281          * re-used by realloc later.
 282          */
 283 }
 284
 285 /*
 286  * Fetch a finished job number from the signal pipe
 287  */
 288
 289 int pthreadpool_finished_job(struct pthreadpool *pool, int *jobid)
 290 {
 291         int ret_jobid;
 292         ssize_t nread;
 293
 294         nread = -1;
 295         errno = EINTR;
 296
 297         while ((nread == -1) && (errno == EINTR)) {
 298                 nread = read(pool->sig_pipe[0], &ret_jobid, sizeof(int));
 299         }
 300         if (nread == -1) {
 301                 return errno;
 302         }
 303         if (nread != sizeof(int)) {
 304                 return EINVAL;
 305         }
 306         *jobid = ret_jobid;
 307         return 0;
 308 }
 309
 310 /*
 311  * Destroy a thread pool, finishing all threads working for it
 312  */
 313
 314 int pthreadpool_destroy(struct pthreadpool *pool)
 315 {
 316         int ret, ret1;
 317
 318         ret = pthread_mutex_lock(&pool->mutex);
 319         if (ret != 0) {
 320                 return ret;
 321         }
 322
 323         if ((pool->jobs != NULL) || pool->shutdown) {
 324                 ret = pthread_mutex_unlock(&pool->mutex);
 325                 assert(ret == 0);
 326                 return EBUSY;
 327         }
 328
 329         if (pool->num_threads > 0) {
 330                 /*
 331                  * We have active threads, tell them to finish, wait for that.
 332                  */
 333
 334                 pool->shutdown = 1;
 335
 336                 if (pool->num_idle > 0) {
 337                         /*
 338                          * Wake the idle threads. They will find pool->quit to
 339                          * be set and exit themselves
 340                          */
 341                         ret = pthread_cond_broadcast(&pool->condvar);
 342                         if (ret != 0) {
 343                                 pthread_mutex_unlock(&pool->mutex);
 344                                 return ret;
 345                         }
 346                 }
 347
 348                 while ((pool->num_threads > 0) || (pool->num_exited > 0)) {
 349
 350                         if (pool->num_exited > 0) {
 351                                 pthreadpool_join_children(pool);
 352                                 continue;
 353                         }
 354                         /*
 355                          * A thread that shuts down will also signal
 356                          * pool->condvar
 357                          */
 358                         ret = pthread_cond_wait(&pool->condvar, &pool->mutex);
 359                         if (ret != 0) {
 360                                 pthread_mutex_unlock(&pool->mutex);
 361                                 return ret;
 362                         }
 363                 }
 364         }
 365
 366         ret = pthread_mutex_unlock(&pool->mutex);
 367         if (ret != 0) {
 368                 return ret;
 369         }
 370         ret = pthread_mutex_destroy(&pool->mutex);
 371         ret1 = pthread_cond_destroy(&pool->condvar);
 372
 373         if (ret != 0) {
 374                 return ret;
 375         }
 376         if (ret1 != 0) {
 377                 return ret1;
 378         }
 379
 380         ret = pthread_mutex_lock(&pthreadpools_mutex);
 381         if (ret != 0) {
 382                 return ret;
 383         }
 384         DLIST_REMOVE(pthreadpools, pool);
 385         ret = pthread_mutex_unlock(&pthreadpools_mutex);
 386         assert(ret == 0);
 387
 388         close(pool->sig_pipe[0]);
 389         pool->sig_pipe[0] = -1;
 390
 391         close(pool->sig_pipe[1]);
 392         pool->sig_pipe[1] = -1;
 393
 394         free(pool->exited);
 395         free(pool);
 396
 397         return 0;
 398 }
 399
 400 /*
 401  * Prepare for pthread_exit(), pool->mutex must be locked
 402  */
 403 static void pthreadpool_server_exit(struct pthreadpool *pool)
 404 {
 405         pthread_t *exited;
 406
 407         pool->num_threads -= 1;
 408
 409         exited = (pthread_t *)realloc(
 410                 pool->exited, sizeof(pthread_t *) * (pool->num_exited + 1));
 411
 412         if (exited == NULL) {
 413                 /* lost a thread status */
 414                 return;
 415         }
 416         pool->exited = exited;
 417
 418         pool->exited[pool->num_exited] = pthread_self();
 419         pool->num_exited += 1;
 420 }
 421
 422 static void *pthreadpool_server(void *arg)
 423 {
 424         struct pthreadpool *pool = (struct pthreadpool *)arg;
 425         int res;
 426
 427         res = pthread_mutex_lock(&pool->mutex);
 428         if (res != 0) {
 429                 return NULL;
 430         }
 431
 432         while (1) {
 433                 struct timespec ts;
 434                 struct pthreadpool_job *job;
 435
 436                 /*
 437                  * idle-wait at most 1 second. If nothing happens in that
 438                  * time, exit this thread.
 439                  */
 440
 441                 clock_gettime(CLOCK_REALTIME, &ts);
 442                 ts.tv_sec += 1;
 443
 444                 while ((pool->jobs == NULL) && (pool->shutdown == 0)) {
 445
 446                         pool->num_idle += 1;
 447                         res = pthread_cond_timedwait(
 448                                 &pool->condvar, &pool->mutex, &ts);
 449                         pool->num_idle -= 1;
 450
 451                         if (res == ETIMEDOUT) {
 452
 453                                 if (pool->jobs == NULL) {
 454                                         /*
 455                                          * we timed out and still no work for
 456                                          * us. Exit.
 457                                          */
 458                                         pthreadpool_server_exit(pool);
 459                                         pthread_mutex_unlock(&pool->mutex);
 460                                         return NULL;
 461                                 }
 462
 463                                 break;
 464                         }
 465                         assert(res == 0);
 466                 }
 467
 468                 job = pool->jobs;
 469
 470                 if (job != NULL) {
 471                         ssize_t written;
 472
 473                         /*
 474                          * Ok, there's work for us to do, remove the job from
 475                          * the pthreadpool list
 476                          */
 477                         pool->jobs = job->next;
 478                         if (pool->last_job == job) {
 479                                 pool->last_job = NULL;
 480                         }
 481
 482                         /*
 483                          * Do the work with the mutex unlocked
 484                          */
 485
 486                         res = pthread_mutex_unlock(&pool->mutex);
 487                         assert(res == 0);
 488
 489                         job->fn(job->private_data);
 490
 491                         written = write(pool->sig_pipe[1], &job->id,
 492                                         sizeof(int));
 493
 494                         free(job);
 495
 496                         res = pthread_mutex_lock(&pool->mutex);
 497                         assert(res == 0);
 498
 499                         if (written != sizeof(int)) {
 500                                 pthreadpool_server_exit(pool);
 501                                 pthread_mutex_unlock(&pool->mutex);
 502                                 return NULL;
 503                         }
 504                 }
 505
 506                 if ((pool->jobs == NULL) && (pool->shutdown != 0)) {
 507                         /*
 508                          * No more work to do and we're asked to shut down, so
 509                          * exit
 510                          */
 511                         pthreadpool_server_exit(pool);
 512
 513                         if (pool->num_threads == 0) {
 514                                 /*
 515                                  * Ping the main thread waiting for all of us
 516                                  * workers to have quit.
 517                                  */
 518                                 pthread_cond_broadcast(&pool->condvar);
 519                         }
 520
 521                         pthread_mutex_unlock(&pool->mutex);
 522                         return NULL;
 523                 }
 524         }
 525 }
 526
 527 int pthreadpool_add_job(struct pthreadpool *pool, int job_id,
 528                         void (*fn)(void *private_data), void *private_data)
 529 {
 530         struct pthreadpool_job *job;
 531         pthread_t thread_id;
 532         int res;
 533         sigset_t mask, omask;
 534
 535         job = (struct pthreadpool_job *)malloc(sizeof(struct pthreadpool_job));
 536         if (job == NULL) {
 537                 return ENOMEM;
 538         }
 539
 540         job->fn = fn;
 541         job->private_data = private_data;
 542         job->id = job_id;
 543         job->next = NULL;
 544
 545         res = pthread_mutex_lock(&pool->mutex);
 546         if (res != 0) {
 547                 free(job);
 548                 return res;
 549         }
 550
 551         if (pool->shutdown) {
 552                 /*
 553                  * Protect against the pool being shut down while
 554                  * trying to add a job
 555                  */
 556                 res = pthread_mutex_unlock(&pool->mutex);
 557                 assert(res == 0);
 558                 free(job);
 559                 return EINVAL;
 560         }
 561
 562         /*
 563          * Just some cleanup under the mutex
 564          */
 565         pthreadpool_join_children(pool);
 566
 567         /*
 568          * Add job to the end of the queue
 569          */
 570         if (pool->jobs == NULL) {
 571                 pool->jobs = job;
 572         }
 573         else {
 574                 pool->last_job->next = job;
 575         }
 576         pool->last_job = job;
 577
 578         if (pool->num_idle > 0) {
 579                 /*
 580                  * We have idle threads, wake one.
 581                  */
 582                 res = pthread_cond_signal(&pool->condvar);
 583                 pthread_mutex_unlock(&pool->mutex);
 584                 return res;
 585         }
 586
 587         if ((pool->max_threads != 0) &&
 588             (pool->num_threads >= pool->max_threads)) {
 589                 /*
 590                  * No more new threads, we just queue the request
 591                  */
 592                 pthread_mutex_unlock(&pool->mutex);
 593                 return 0;
 594         }
 595
 596         /*
 597          * Create a new worker thread. It should not receive any signals.
 598          */
 599
 600         sigfillset(&mask);
 601
 602         res = pthread_sigmask(SIG_BLOCK, &mask, &omask);
 603         if (res != 0) {
 604                 pthread_mutex_unlock(&pool->mutex);
 605                 return res;
 606         }
 607
 608         res = pthread_create(&thread_id, NULL, pthreadpool_server,
 609                                 (void *)pool);
 610         if (res == 0) {
 611                 pool->num_threads += 1;
 612         }
 613
 614         assert(pthread_sigmask(SIG_SETMASK, &omask, NULL) == 0);
 615
 616         pthread_mutex_unlock(&pool->mutex);
 617         return res;
 618 }