glib/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);
  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 {
 167   gboolean success = FALSE;
 168   GThreadPriority priority = pool->pool.priority;
 169   GAsyncQueue *queue = unused_thread_queue[priority];
 170
 171   if (pool->num_threads >= pool->max_threads && pool->max_threads != -1)
 172     /* Enough threads are already running */
 173     return;
 174
 175   g_async_queue_lock (queue);
 176
 177   if (g_async_queue_length_unlocked (queue) < 0)
 178     {
 179       /* First we try a thread with the right priority */
 180       g_async_queue_push_unlocked (queue, pool);
 181       success = TRUE;
 182     }
 183
 184   g_async_queue_unlock (queue);
 185
 186   if (!success)
 187     {
 188       /* Now we search for threads with other priorities too, but
 189        * only, when there is more than one unused thread with that
 190        * priority. */
 191       GThreadPriority priority;
 192       for (priority = G_THREAD_PRIORITY_LOW;
 193            priority < G_THREAD_PRIORITY_URGENT + 1; priority++)
 194         {
 195           queue = unused_thread_queue[priority];
 196           g_async_queue_lock (queue);
 197
 198           if (g_async_queue_length_unlocked (queue) < -1)
 199             {
 200               g_async_queue_push_unlocked (queue, pool);
 201               success = TRUE;
 202             }
 203
 204           g_async_queue_unlock (queue);
 205         }
 206     }
 207
 208   if (!success)
 209     /* No thread was found, we have to start one new */
 210     g_thread_create (g_thread_pool_thread_proxy, pool, pool->pool.stack_size,
 211                      FALSE, pool->pool.bound, priority);
 212
 213   /* See comment in g_thread_pool_thread_proxy as to why this is done
 214    * here and not there */
 215   pool->num_threads++;
 216 }
 217
 218 GThreadPool*
 219 g_thread_pool_new (GFunc            thread_func,
 220                    gint             max_threads,
 221                    gulong           stack_size,
 222                    gboolean         bound,
 223                    GThreadPriority  priority,
 224                    gboolean         exclusive,
 225                    gpointer         user_data)
 226 {
 227   GRealThreadPool *retval;
 228
 229   g_return_val_if_fail (thread_func, NULL);
 230   g_return_val_if_fail (!exclusive || max_threads != -1, NULL);
 231   g_return_val_if_fail (max_threads >= -1, NULL);
 232   g_return_val_if_fail (g_thread_supported (), NULL);
 233
 234   retval = g_new (GRealThreadPool, 1);
 235
 236   retval->pool.thread_func = thread_func;
 237   retval->pool.stack_size = stack_size;
 238   retval->pool.bound = bound;
 239   retval->pool.priority = priority;
 240   retval->pool.exclusive = exclusive;
 241   retval->pool.user_data = user_data;
 242
 243   retval->queue = g_async_queue_new ();
 244   retval->max_threads = max_threads;
 245   retval->num_threads = 0;
 246   retval->running = TRUE;
 247
 248   if (!inform_mutex)
 249     {
 250       inform_mutex = g_mutex_new ();
 251       inform_cond = g_cond_new ();
 252       for (priority = G_THREAD_PRIORITY_LOW;
 253            priority < G_THREAD_PRIORITY_URGENT + 1; priority++)
 254         unused_thread_queue[priority] = g_async_queue_new ();
 255     }
 256
 257   if (retval->pool.exclusive)
 258     {
 259       g_async_queue_lock (retval->queue);
 260
 261       while (retval->num_threads < retval->max_threads)
 262         g_thread_pool_start_thread (retval);
 263
 264       g_async_queue_unlock (retval->queue);
 265     }
 266
 267   return (GThreadPool*) retval;
 268 }
 269
 270 void
 271 g_thread_pool_push (GThreadPool     *pool,
 272                     gpointer         data)
 273 {
 274   GRealThreadPool *real = (GRealThreadPool*) pool;
 275
 276   g_return_if_fail (real);
 277
 278   g_async_queue_lock (real->queue);
 279
 280   if (!real->running)
 281     {
 282       g_async_queue_unlock (real->queue);
 283       g_return_if_fail (real->running);
 284     }
 285
 286   if (!pool->exclusive && g_async_queue_length_unlocked (real->queue) >= 0)
 287     {
 288       /* No thread is waiting in the queue */
 289       g_thread_pool_start_thread (real);
 290     }
 291   g_async_queue_push_unlocked (real->queue, data);
 292   g_async_queue_unlock (real->queue);
 293 }
 294
 295 void
 296 g_thread_pool_set_max_threads (GThreadPool     *pool,
 297                                gint             max_threads)
 298 {
 299   GRealThreadPool *real = (GRealThreadPool*) pool;
 300   gint to_start;
 301
 302   g_return_if_fail (real);
 303   g_return_if_fail (real->running);
 304   g_return_if_fail (!real->pool.exclusive || max_threads != -1);
 305   g_return_if_fail (max_threads >= -1);
 306
 307   g_async_queue_lock (real->queue);
 308
 309   real->max_threads = max_threads;
 310
 311   if (pool->exclusive)
 312     to_start = real->max_threads - real->num_threads;
 313   else
 314     to_start = g_async_queue_length_unlocked (real->queue);
 315
 316   for ( ; to_start > 0; to_start--)
 317     g_thread_pool_start_thread (real);
 318
 319   g_async_queue_unlock (real->queue);
 320 }
 321
 322 gint
 323 g_thread_pool_get_max_threads (GThreadPool     *pool)
 324 {
 325   GRealThreadPool *real = (GRealThreadPool*) pool;
 326   gint retval;
 327
 328   g_return_val_if_fail (real, 0);
 329   g_return_val_if_fail (real->running, 0);
 330
 331   g_async_queue_lock (real->queue);
 332
 333   retval = real->max_threads;
 334
 335   g_async_queue_unlock (real->queue);
 336
 337   return retval;
 338 }
 339
 340 guint
 341 g_thread_pool_get_num_threads (GThreadPool     *pool)
 342 {
 343   GRealThreadPool *real = (GRealThreadPool*) pool;
 344   guint retval;
 345
 346   g_return_val_if_fail (real, 0);
 347   g_return_val_if_fail (real->running, 0);
 348
 349   g_async_queue_lock (real->queue);
 350
 351   retval = real->num_threads;
 352
 353   g_async_queue_unlock (real->queue);
 354
 355   return retval;
 356 }
 357
 358 guint
 359 g_thread_pool_unprocessed (GThreadPool     *pool)
 360 {
 361   GRealThreadPool *real = (GRealThreadPool*) pool;
 362   gint unprocessed;
 363
 364   g_return_val_if_fail (real, 0);
 365   g_return_val_if_fail (real->running, 0);
 366
 367   unprocessed = g_async_queue_length (real->queue);
 368
 369   return MAX (unprocessed, 0);
 370 }
 371
 372 void
 373 g_thread_pool_free (GThreadPool     *pool,
 374                     gboolean         immediate,
 375                     gboolean         wait)
 376 {
 377   GRealThreadPool *real = (GRealThreadPool*) pool;
 378
 379   g_return_if_fail (real);
 380   g_return_if_fail (real->running);
 381   /* It there's no thread allowed here, there is not much sense in
 382    * not stopping this pool immediatly, when it's not empty */
 383   g_return_if_fail (immediate || real->max_threads != 0 ||
 384                     g_async_queue_length (real->queue) == 0);
 385
 386   g_async_queue_lock (real->queue);
 387
 388   real->running = FALSE;
 389   real->immediate = immediate;
 390   real->waiting = wait;
 391
 392   if (wait)
 393     {
 394       g_mutex_lock (inform_mutex);
 395       while (g_async_queue_length_unlocked (real->queue) != -real->num_threads)
 396         {
 397           g_async_queue_unlock (real->queue);
 398           g_cond_wait (inform_cond, inform_mutex);
 399           g_async_queue_lock (real->queue);
 400         }
 401       g_mutex_unlock (inform_mutex);
 402     }
 403
 404   if (g_async_queue_length_unlocked (real->queue) == -real->num_threads)
 405     {
 406       /* No thread is currently doing something (and nothing is left
 407        * to process in the queue) */
 408       if (real->num_threads == 0) /* No threads left, we clean up */
 409         {
 410           g_async_queue_unlock (real->queue);
 411           g_thread_pool_free_internal (real);
 412           return;
 413         }
 414
 415       g_thread_pool_wakeup_and_stop_all (real);
 416     }
 417
 418   real->waiting = FALSE; /* The last thread should cleanup the pool */
 419   g_async_queue_unlock (real->queue);
 420 }
 421
 422 static void
 423 g_thread_pool_free_internal (GRealThreadPool* pool)
 424 {
 425   g_return_if_fail (pool);
 426   g_return_if_fail (!pool->running);
 427   g_return_if_fail (pool->num_threads == 0);
 428
 429   g_async_queue_unref (pool->queue);
 430
 431   g_free (pool);
 432 }
 433
 434 static void
 435 g_thread_pool_wakeup_and_stop_all (GRealThreadPool* pool)
 436 {
 437   guint i;
 438
 439   g_return_if_fail (pool);
 440   g_return_if_fail (!pool->running);
 441   g_return_if_fail (pool->num_threads != 0);
 442   g_return_if_fail (g_async_queue_length_unlocked (pool->queue) ==
 443                     -pool->num_threads);
 444
 445   pool->immediate = TRUE;
 446   for (i = 0; i < pool->num_threads; i++)
 447     g_async_queue_push_unlocked (pool->queue, GUINT_TO_POINTER (1));
 448 }
 449
 450 void
 451 g_thread_pool_set_max_unused_threads (gint max_threads)
 452 {
 453   g_return_if_fail (max_threads >= -1);
 454
 455   G_LOCK (unused_threads);
 456
 457   max_unused_threads = max_threads;
 458
 459   if (max_unused_threads < unused_threads && max_unused_threads != -1)
 460     {
 461       guint close_down_num = unused_threads - max_unused_threads;
 462       GThreadPriority priority;
 463
 464       while (close_down_num > 0)
 465         {
 466           guint old_close_down_num = close_down_num;
 467           for (priority = G_THREAD_PRIORITY_LOW;
 468                priority < G_THREAD_PRIORITY_URGENT + 1 && close_down_num > 0;
 469                priority++)
 470             {
 471               GAsyncQueue *queue = unused_thread_queue[priority];
 472               g_async_queue_lock (queue);
 473
 474               if (g_async_queue_length_unlocked (queue) < 0)
 475                 {
 476                   g_async_queue_push_unlocked (queue,
 477                                                stop_this_thread_marker);
 478                   close_down_num--;
 479                 }
 480
 481               g_async_queue_unlock (queue);
 482             }
 483
 484           /* Just to make sure, there are no counting problems */
 485           g_assert (old_close_down_num != close_down_num);
 486         }
 487     }
 488
 489   G_UNLOCK (unused_threads);
 490 }
 491
 492 gint
 493 g_thread_pool_get_max_unused_threads (void)
 494 {
 495   gint retval;
 496
 497   G_LOCK (unused_threads);
 498   retval = max_unused_threads;
 499   G_UNLOCK (unused_threads);
 500
 501   return retval;
 502 }
 503
 504 guint g_thread_pool_get_num_unused_threads (void)
 505 {
 506   guint retval;
 507
 508   G_LOCK (unused_threads);
 509   retval = unused_threads;
 510   G_UNLOCK (unused_threads);
 511
 512   return retval;
 513 }
 514
 515 void g_thread_pool_stop_unused_threads (void)
 516 {
 517   guint oldval = g_thread_pool_get_max_unused_threads ();
 518   g_thread_pool_set_max_unused_threads (0);
 519   g_thread_pool_set_max_unused_threads (oldval);
 520 }