gthreadpool.c

   1 /* GLIB - Library of useful routines for C programming
   2  * Copyright (C) 1995-1997  Peter Mattis, Spencer Kimball and Josh MacDonald
   3  *
   4  * GAsyncQueue: thread pool implementation.
   5  * Copyright (C) 2000 Sebastian Wilhelmi; University of Karlsruhe
   6  *
   7  * This library is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU Lesser General Public
   9  * License as published by the Free Software Foundation; either
  10  * version 2 of the License, or (at your option) any later version.
  11  *
  12  * This library is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15  * Lesser General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU Lesser General Public
  18  * License along with this library; if not, write to the
  19  * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  20  * Boston, MA 02111-1307, USA.
  21  */
  22
  23 /*
  24  * MT safe
  25  */
  26
  27 #include "glib.h"
  28
  29 typedef struct _GRealThreadPool GRealThreadPool;
  30
  31 struct _GRealThreadPool
  32 {
  33   GThreadPool pool;
  34   GAsyncQueue* queue;
  35   gint max_threads;
  36   gint num_threads;
  37   gboolean running;
  38   gboolean immediate;
  39   gboolean waiting;
  40 };
  41
  42 /* The following is just an address to mark the stop order for a
  43  * thread, it could be any address (as long, as it isn;t a valid
  44  * GThreadPool address) */
  45 static const gpointer stop_this_thread_marker = &g_thread_pool_new;
  46
  47 /* Here all unused threads are waiting, depending on their priority */
  48 static GAsyncQueue *unused_thread_queue[G_THREAD_PRIORITY_URGENT + 1];
  49 static gint unused_threads = 0;
  50 static gint max_unused_threads = 0;
  51 G_LOCK_DEFINE_STATIC (unused_threads);
  52
  53 static GMutex *inform_mutex = NULL;
  54 static GCond *inform_cond = NULL;
  55
  56 static void g_thread_pool_free_internal (GRealThreadPool* pool);
  57 static void g_thread_pool_thread_proxy (gpointer data);
  58 static void g_thread_pool_start_thread (GRealThreadPool* pool, GError **error);
  59 static void g_thread_pool_wakeup_and_stop_all (GRealThreadPool* pool);
  60
  61 #define g_thread_should_run(pool, len) \
  62   ((pool)->running || (!(pool)->immediate && (len) > 0))
  63
  64 static void
  65 g_thread_pool_thread_proxy (gpointer data)
  66 {
  67   GRealThreadPool *pool = data;
  68   GThread* self = g_thread_self ();
  69
  70   g_async_queue_lock (pool->queue);
  71   while (TRUE)
  72     {
  73       gpointer task;
  74       gboolean goto_global_pool = !pool->pool.exclusive;
  75       gint len = g_async_queue_length_unlocked (pool->queue);
  76
  77       if (g_thread_should_run (pool, len))
  78         {
  79           task = g_async_queue_pop_unlocked (pool->queue);
  80
  81           if (pool->num_threads > pool->max_threads && pool->max_threads != -1)
  82             /* We are in fact a superfluous threads, so we go to the
  83              * global pool and just hand the data further to the next one
  84              * waiting in the queue */
  85             {
  86               g_async_queue_push_unlocked (pool->queue, task);
  87               goto_global_pool = TRUE;
  88             }
  89           else if (pool->running || !pool->immediate)
  90             {
  91               g_async_queue_unlock (pool->queue);
  92               pool->pool.thread_func (task, pool->pool.user_data);
  93               g_async_queue_lock (pool->queue);
  94             }
  95
  96           len = g_async_queue_length_unlocked (pool->queue);
  97         }
  98
  99       if (!g_thread_should_run (pool, len))
 100         g_cond_broadcast (inform_cond);
 101
 102       if (!pool->running && (pool->immediate || len <= 0))
 103         goto_global_pool = TRUE;
 104       else if (len >= 0)
 105         /* At this pool there is no thread waiting */
 106         goto_global_pool = FALSE;
 107
 108       if (goto_global_pool)
 109         {
 110           GThreadPriority priority = pool->pool.priority;
 111           pool->num_threads--;
 112
 113           if (!pool->running && !pool->waiting)
 114             {
 115               if (pool->num_threads == 0)
 116                 {
 117                   g_async_queue_unlock (pool->queue);
 118                   g_thread_pool_free_internal (pool);
 119                 }
 120               else if (len == - pool->num_threads)
 121                 g_thread_pool_wakeup_and_stop_all (pool);
 122             }
 123           else
 124             g_async_queue_unlock (pool->queue);
 125
 126           g_async_queue_lock (unused_thread_queue[priority]);
 127
 128           G_LOCK (unused_threads);
 129           if (unused_threads >= max_unused_threads)
 130             {
 131               G_UNLOCK (unused_threads);
 132               g_async_queue_unlock (unused_thread_queue[priority]);
 133               /* Stop this thread */
 134               return;
 135             }
 136           unused_threads++;
 137           G_UNLOCK (unused_threads);
 138
 139           pool =
 140             g_async_queue_pop_unlocked (unused_thread_queue[priority]);
 141
 142           G_LOCK (unused_threads);
 143           unused_threads--;
 144           G_UNLOCK (unused_threads);
 145
 146           g_async_queue_unlock (unused_thread_queue[priority]);
 147
 148           if (pool == stop_this_thread_marker)
 149             /* Stop this thread */
 150             return;
 151
 152           g_async_queue_lock (pool->queue);
 153
 154           if (pool->pool.priority != self->priority)
 155             g_thread_set_priority (self, pool->pool.priority);
 156
 157           /* pool->num_threads++ is not done here, but in
 158            * g_thread_pool_start_thread to make the new started thread
 159            * known to the pool, before itself can do it. */
 160         }
 161     }
 162 }
 163
 164 static void
 165 g_thread_pool_start_thread (GRealThreadPool  *pool,
 166                             GError          **error)
 167 {
 168   gboolean success = FALSE;
 169   GThreadPriority priority = pool->pool.priority;
 170   GAsyncQueue *queue = unused_thread_queue[priority];
 171
 172   if (pool->num_threads >= pool->max_threads && pool->max_threads != -1)
 173     /* Enough threads are already running */
 174     return;
 175
 176   g_async_queue_lock (queue);
 177
 178   if (g_async_queue_length_unlocked (queue) < 0)
 179     {
 180       /* First we try a thread with the right priority */
 181       g_async_queue_push_unlocked (queue, pool);
 182       success = TRUE;
 183     }
 184
 185   g_async_queue_unlock (queue);
 186
 187   if (!success)
 188     {
 189       /* Now we search for threads with other priorities too, but
 190        * only, when there is more than one unused thread with that
 191        * priority. */
 192       GThreadPriority priority;
 193       for (priority = G_THREAD_PRIORITY_LOW;
 194            priority < G_THREAD_PRIORITY_URGENT + 1; priority++)
 195         {
 196           queue = unused_thread_queue[priority];
 197           g_async_queue_lock (queue);
 198
 199           if (g_async_queue_length_unlocked (queue) < -1)
 200             {
 201               g_async_queue_push_unlocked (queue, pool);
 202               success = TRUE;
 203             }
 204
 205           g_async_queue_unlock (queue);
 206         }
 207     }
 208
 209   if (!success)
 210     {
 211       GError *local_error = NULL;
 212       /* No thread was found, we have to start one new */
 213       g_thread_create (g_thread_pool_thread_proxy, pool,
 214                        pool->pool.stack_size, FALSE,
 215                        pool->pool.bound, priority, &local_error);
 216
 217       if (local_error)
 218         {
 219           g_propagate_error (error, local_error);
 220           return;
 221         }
 222     }
 223
 224   /* See comment in g_thread_pool_thread_proxy as to why this is done
 225    * here and not there */
 226   pool->num_threads++;
 227 }
 228
 229 GThreadPool*
 230 g_thread_pool_new (GFunc            thread_func,
 231                    gint             max_threads,
 232                    gulong           stack_size,
 233                    gboolean         bound,
 234                    GThreadPriority  priority,
 235                    gboolean         exclusive,
 236                    gpointer         user_data,
 237                    GError         **error)
 238 {
 239   GRealThreadPool *retval;
 240
 241   g_return_val_if_fail (thread_func, NULL);
 242   g_return_val_if_fail (!exclusive || max_threads != -1, NULL);
 243   g_return_val_if_fail (max_threads >= -1, NULL);
 244   g_return_val_if_fail (g_thread_supported (), NULL);
 245
 246   retval = g_new (GRealThreadPool, 1);
 247
 248   retval->pool.thread_func = thread_func;
 249   retval->pool.stack_size = stack_size;
 250   retval->pool.bound = bound;
 251   retval->pool.priority = priority;
 252   retval->pool.exclusive = exclusive;
 253   retval->pool.user_data = user_data;
 254
 255   retval->queue = g_async_queue_new ();
 256   retval->max_threads = max_threads;
 257   retval->num_threads = 0;
 258   retval->running = TRUE;
 259
 260   if (!inform_mutex)
 261     {
 262       inform_mutex = g_mutex_new ();
 263       inform_cond = g_cond_new ();
 264       for (priority = G_THREAD_PRIORITY_LOW;
 265            priority < G_THREAD_PRIORITY_URGENT + 1; priority++)
 266         unused_thread_queue[priority] = g_async_queue_new ();
 267     }
 268
 269   if (retval->pool.exclusive)
 270     {
 271       g_async_queue_lock (retval->queue);
 272
 273       while (retval->num_threads < retval->max_threads)
 274         {
 275           GError *local_error = NULL;
 276           g_thread_pool_start_thread (retval, &local_error);
 277           if (local_error)
 278             {
 279               g_propagate_error (error, local_error);
 280               break;
 281             }
 282         }
 283
 284       g_async_queue_unlock (retval->queue);
 285     }
 286
 287   return (GThreadPool*) retval;
 288 }
 289
 290 void
 291 g_thread_pool_push (GThreadPool     *pool,
 292                     gpointer         data,
 293                     GError         **error)
 294 {
 295   GRealThreadPool *real = (GRealThreadPool*) pool;
 296
 297   g_return_if_fail (real);
 298
 299   g_async_queue_lock (real->queue);
 300
 301   if (!real->running)
 302     {
 303       g_async_queue_unlock (real->queue);
 304       g_return_if_fail (real->running);
 305     }
 306
 307   if (!pool->exclusive && g_async_queue_length_unlocked (real->queue) >= 0)
 308     /* No thread is waiting in the queue */
 309     g_thread_pool_start_thread (real, error);
 310
 311   g_async_queue_push_unlocked (real->queue, data);
 312   g_async_queue_unlock (real->queue);
 313 }
 314
 315 void
 316 g_thread_pool_set_max_threads (GThreadPool     *pool,
 317                                gint             max_threads,
 318                                GError         **error)
 319 {
 320   GRealThreadPool *real = (GRealThreadPool*) pool;
 321   gint to_start;
 322
 323   g_return_if_fail (real);
 324   g_return_if_fail (real->running);
 325   g_return_if_fail (!real->pool.exclusive || max_threads != -1);
 326   g_return_if_fail (max_threads >= -1);
 327
 328   g_async_queue_lock (real->queue);
 329
 330   real->max_threads = max_threads;
 331
 332   if (pool->exclusive)
 333     to_start = real->max_threads - real->num_threads;
 334   else
 335     to_start = g_async_queue_length_unlocked (real->queue);
 336
 337   for ( ; to_start > 0; to_start--)
 338     {
 339       GError *local_error = NULL;
 340       g_thread_pool_start_thread (real, &local_error);
 341       if (local_error)
 342         {
 343           g_propagate_error (error, local_error);
 344           break;
 345         }
 346     }
 347
 348   g_async_queue_unlock (real->queue);
 349 }
 350
 351 gint
 352 g_thread_pool_get_max_threads (GThreadPool     *pool)
 353 {
 354   GRealThreadPool *real = (GRealThreadPool*) pool;
 355   gint retval;
 356
 357   g_return_val_if_fail (real, 0);
 358   g_return_val_if_fail (real->running, 0);
 359
 360   g_async_queue_lock (real->queue);
 361
 362   retval = real->max_threads;
 363
 364   g_async_queue_unlock (real->queue);
 365
 366   return retval;
 367 }
 368
 369 guint
 370 g_thread_pool_get_num_threads (GThreadPool     *pool)
 371 {
 372   GRealThreadPool *real = (GRealThreadPool*) pool;
 373   guint retval;
 374
 375   g_return_val_if_fail (real, 0);
 376   g_return_val_if_fail (real->running, 0);
 377
 378   g_async_queue_lock (real->queue);
 379
 380   retval = real->num_threads;
 381
 382   g_async_queue_unlock (real->queue);
 383
 384   return retval;
 385 }
 386
 387 guint
 388 g_thread_pool_unprocessed (GThreadPool     *pool)
 389 {
 390   GRealThreadPool *real = (GRealThreadPool*) pool;
 391   gint unprocessed;
 392
 393   g_return_val_if_fail (real, 0);
 394   g_return_val_if_fail (real->running, 0);
 395
 396   unprocessed = g_async_queue_length (real->queue);
 397
 398   return MAX (unprocessed, 0);
 399 }
 400
 401 void
 402 g_thread_pool_free (GThreadPool     *pool,
 403                     gboolean         immediate,
 404                     gboolean         wait)
 405 {
 406   GRealThreadPool *real = (GRealThreadPool*) pool;
 407
 408   g_return_if_fail (real);
 409   g_return_if_fail (real->running);
 410   /* It there's no thread allowed here, there is not much sense in
 411    * not stopping this pool immediatly, when it's not empty */
 412   g_return_if_fail (immediate || real->max_threads != 0 ||
 413                     g_async_queue_length (real->queue) == 0);
 414
 415   g_async_queue_lock (real->queue);
 416
 417   real->running = FALSE;
 418   real->immediate = immediate;
 419   real->waiting = wait;
 420
 421   if (wait)
 422     {
 423       g_mutex_lock (inform_mutex);
 424       while (g_async_queue_length_unlocked (real->queue) != -real->num_threads)
 425         {
 426           g_async_queue_unlock (real->queue);
 427           g_cond_wait (inform_cond, inform_mutex);
 428           g_async_queue_lock (real->queue);
 429         }
 430       g_mutex_unlock (inform_mutex);
 431     }
 432
 433   if (g_async_queue_length_unlocked (real->queue) == -real->num_threads)
 434     {
 435       /* No thread is currently doing something (and nothing is left
 436        * to process in the queue) */
 437       if (real->num_threads == 0) /* No threads left, we clean up */
 438         {
 439           g_async_queue_unlock (real->queue);
 440           g_thread_pool_free_internal (real);
 441           return;
 442         }
 443
 444       g_thread_pool_wakeup_and_stop_all (real);
 445     }
 446
 447   real->waiting = FALSE; /* The last thread should cleanup the pool */
 448   g_async_queue_unlock (real->queue);
 449 }
 450
 451 static void
 452 g_thread_pool_free_internal (GRealThreadPool* pool)
 453 {
 454   g_return_if_fail (pool);
 455   g_return_if_fail (!pool->running);
 456   g_return_if_fail (pool->num_threads == 0);
 457
 458   g_async_queue_unref (pool->queue);
 459
 460   g_free (pool);
 461 }
 462
 463 static void
 464 g_thread_pool_wakeup_and_stop_all (GRealThreadPool* pool)
 465 {
 466   guint i;
 467
 468   g_return_if_fail (pool);
 469   g_return_if_fail (!pool->running);
 470   g_return_if_fail (pool->num_threads != 0);
 471   g_return_if_fail (g_async_queue_length_unlocked (pool->queue) ==
 472                     -pool->num_threads);
 473
 474   pool->immediate = TRUE;
 475   for (i = 0; i < pool->num_threads; i++)
 476     g_async_queue_push_unlocked (pool->queue, GUINT_TO_POINTER (1));
 477 }
 478
 479 void
 480 g_thread_pool_set_max_unused_threads (gint max_threads)
 481 {
 482   g_return_if_fail (max_threads >= -1);
 483
 484   G_LOCK (unused_threads);
 485
 486   max_unused_threads = max_threads;
 487
 488   if (max_unused_threads < unused_threads && max_unused_threads != -1)
 489     {
 490       guint close_down_num = unused_threads - max_unused_threads;
 491       GThreadPriority priority;
 492
 493       while (close_down_num > 0)
 494         {
 495           guint old_close_down_num = close_down_num;
 496           for (priority = G_THREAD_PRIORITY_LOW;
 497                priority < G_THREAD_PRIORITY_URGENT + 1 && close_down_num > 0;
 498                priority++)
 499             {
 500               GAsyncQueue *queue = unused_thread_queue[priority];
 501               g_async_queue_lock (queue);
 502
 503               if (g_async_queue_length_unlocked (queue) < 0)
 504                 {
 505                   g_async_queue_push_unlocked (queue,
 506                                                stop_this_thread_marker);
 507                   close_down_num--;
 508                 }
 509
 510               g_async_queue_unlock (queue);
 511             }
 512
 513           /* Just to make sure, there are no counting problems */
 514           g_assert (old_close_down_num != close_down_num);
 515         }
 516     }
 517
 518   G_UNLOCK (unused_threads);
 519 }
 520
 521 gint
 522 g_thread_pool_get_max_unused_threads (void)
 523 {
 524   gint retval;
 525
 526   G_LOCK (unused_threads);
 527   retval = max_unused_threads;
 528   G_UNLOCK (unused_threads);
 529
 530   return retval;
 531 }
 532
 533 guint g_thread_pool_get_num_unused_threads (void)
 534 {
 535   guint retval;
 536
 537   G_LOCK (unused_threads);
 538   retval = unused_threads;
 539   G_UNLOCK (unused_threads);
 540
 541   return retval;
 542 }
 543
 544 void g_thread_pool_stop_unused_threads (void)
 545 {
 546   guint oldval = g_thread_pool_get_max_unused_threads ();
 547   g_thread_pool_set_max_unused_threads (0);
 548   g_thread_pool_set_max_unused_threads (oldval);
 549 }