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 = (gpointer) &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           /* pool->num_threads++ is not done here, but in
 155            * g_thread_pool_start_thread to make the new started thread
 156            * known to the pool, before itself can do it. */
 157         }
 158     }
 159 }
 160
 161 static void
 162 g_thread_pool_start_thread (GRealThreadPool  *pool,
 163                             GError          **error)
 164 {
 165   gboolean success = FALSE;
 166   GThreadPriority priority = pool->pool.priority;
 167   GAsyncQueue *queue = unused_thread_queue[priority];
 168
 169   if (pool->num_threads >= pool->max_threads && pool->max_threads != -1)
 170     /* Enough threads are already running */
 171     return;
 172
 173   g_async_queue_lock (queue);
 174
 175   if (g_async_queue_length_unlocked (queue) < 0)
 176     {
 177       /* First we try a thread with the right priority */
 178       g_async_queue_push_unlocked (queue, pool);
 179       success = TRUE;
 180     }
 181
 182   g_async_queue_unlock (queue);
 183
 184   /* We will not search for threads with other priorities, because changing
 185    * priority is quite unportable */
 186
 187   if (!success)
 188     {
 189       GError *local_error = NULL;
 190       /* No thread was found, we have to start one new */
 191       g_thread_create (g_thread_pool_thread_proxy, pool,
 192                        pool->pool.stack_size, FALSE,
 193                        pool->pool.bound, priority, &local_error);
 194
 195       if (local_error)
 196         {
 197           g_propagate_error (error, local_error);
 198           return;
 199         }
 200     }
 201
 202   /* See comment in g_thread_pool_thread_proxy as to why this is done
 203    * here and not there */
 204   pool->num_threads++;
 205 }
 206
 207 GThreadPool*
 208 g_thread_pool_new (GFunc            thread_func,
 209                    gint             max_threads,
 210                    gulong           stack_size,
 211                    gboolean         bound,
 212                    GThreadPriority  priority,
 213                    gboolean         exclusive,
 214                    gpointer         user_data,
 215                    GError         **error)
 216 {
 217   GRealThreadPool *retval;
 218
 219   g_return_val_if_fail (thread_func, NULL);
 220   g_return_val_if_fail (!exclusive || max_threads != -1, NULL);
 221   g_return_val_if_fail (max_threads >= -1, NULL);
 222   g_return_val_if_fail (g_thread_supported (), NULL);
 223
 224   retval = g_new (GRealThreadPool, 1);
 225
 226   retval->pool.thread_func = thread_func;
 227   retval->pool.stack_size = stack_size;
 228   retval->pool.bound = bound;
 229   retval->pool.priority = priority;
 230   retval->pool.exclusive = exclusive;
 231   retval->pool.user_data = user_data;
 232   retval->queue = g_async_queue_new ();
 233   retval->max_threads = max_threads;
 234   retval->num_threads = 0;
 235   retval->running = TRUE;
 236
 237   if (!inform_mutex)
 238     {
 239       inform_mutex = g_mutex_new ();
 240       inform_cond = g_cond_new ();
 241       for (priority = G_THREAD_PRIORITY_LOW;
 242            priority < G_THREAD_PRIORITY_URGENT + 1; priority++)
 243         unused_thread_queue[priority] = g_async_queue_new ();
 244     }
 245
 246   if (retval->pool.exclusive)
 247     {
 248       g_async_queue_lock (retval->queue);
 249
 250       while (retval->num_threads < retval->max_threads)
 251         {
 252           GError *local_error = NULL;
 253           g_thread_pool_start_thread (retval, &local_error);
 254           if (local_error)
 255             {
 256               g_propagate_error (error, local_error);
 257               break;
 258             }
 259         }
 260
 261       g_async_queue_unlock (retval->queue);
 262     }
 263
 264   return (GThreadPool*) retval;
 265 }
 266
 267 void
 268 g_thread_pool_push (GThreadPool     *pool,
 269                     gpointer         data,
 270                     GError         **error)
 271 {
 272   GRealThreadPool *real = (GRealThreadPool*) pool;
 273
 274   g_return_if_fail (real);
 275
 276   g_async_queue_lock (real->queue);
 277
 278   if (!real->running)
 279     {
 280       g_async_queue_unlock (real->queue);
 281       g_return_if_fail (real->running);
 282     }
 283
 284   if (!pool->exclusive && g_async_queue_length_unlocked (real->queue) >= 0)
 285     /* No thread is waiting in the queue */
 286     g_thread_pool_start_thread (real, error);
 287
 288   g_async_queue_push_unlocked (real->queue, data);
 289   g_async_queue_unlock (real->queue);
 290 }
 291
 292 void
 293 g_thread_pool_set_max_threads (GThreadPool     *pool,
 294                                gint             max_threads,
 295                                GError         **error)
 296 {
 297   GRealThreadPool *real = (GRealThreadPool*) pool;
 298   gint to_start;
 299
 300   g_return_if_fail (real);
 301   g_return_if_fail (real->running);
 302   g_return_if_fail (!real->pool.exclusive || max_threads != -1);
 303   g_return_if_fail (max_threads >= -1);
 304
 305   g_async_queue_lock (real->queue);
 306
 307   real->max_threads = max_threads;
 308
 309   if (pool->exclusive)
 310     to_start = real->max_threads - real->num_threads;
 311   else
 312     to_start = g_async_queue_length_unlocked (real->queue);
 313
 314   for ( ; to_start > 0; to_start--)
 315     {
 316       GError *local_error = NULL;
 317       g_thread_pool_start_thread (real, &local_error);
 318       if (local_error)
 319         {
 320           g_propagate_error (error, local_error);
 321           break;
 322         }
 323     }
 324
 325   g_async_queue_unlock (real->queue);
 326 }
 327
 328 gint
 329 g_thread_pool_get_max_threads (GThreadPool     *pool)
 330 {
 331   GRealThreadPool *real = (GRealThreadPool*) pool;
 332   gint retval;
 333
 334   g_return_val_if_fail (real, 0);
 335   g_return_val_if_fail (real->running, 0);
 336
 337   g_async_queue_lock (real->queue);
 338
 339   retval = real->max_threads;
 340
 341   g_async_queue_unlock (real->queue);
 342
 343   return retval;
 344 }
 345
 346 guint
 347 g_thread_pool_get_num_threads (GThreadPool     *pool)
 348 {
 349   GRealThreadPool *real = (GRealThreadPool*) pool;
 350   guint retval;
 351
 352   g_return_val_if_fail (real, 0);
 353   g_return_val_if_fail (real->running, 0);
 354
 355   g_async_queue_lock (real->queue);
 356
 357   retval = real->num_threads;
 358
 359   g_async_queue_unlock (real->queue);
 360
 361   return retval;
 362 }
 363
 364 guint
 365 g_thread_pool_unprocessed (GThreadPool     *pool)
 366 {
 367   GRealThreadPool *real = (GRealThreadPool*) pool;
 368   gint unprocessed;
 369
 370   g_return_val_if_fail (real, 0);
 371   g_return_val_if_fail (real->running, 0);
 372
 373   unprocessed = g_async_queue_length (real->queue);
 374
 375   return MAX (unprocessed, 0);
 376 }
 377
 378 void
 379 g_thread_pool_free (GThreadPool     *pool,
 380                     gboolean         immediate,
 381                     gboolean         wait)
 382 {
 383   GRealThreadPool *real = (GRealThreadPool*) pool;
 384
 385   g_return_if_fail (real);
 386   g_return_if_fail (real->running);
 387   /* It there's no thread allowed here, there is not much sense in
 388    * not stopping this pool immediatly, when it's not empty */
 389   g_return_if_fail (immediate || real->max_threads != 0 ||
 390                     g_async_queue_length (real->queue) == 0);
 391
 392   g_async_queue_lock (real->queue);
 393
 394   real->running = FALSE;
 395   real->immediate = immediate;
 396   real->waiting = wait;
 397
 398   if (wait)
 399     {
 400       g_mutex_lock (inform_mutex);
 401       while (g_async_queue_length_unlocked (real->queue) != -real->num_threads)
 402         {
 403           g_async_queue_unlock (real->queue);
 404           g_cond_wait (inform_cond, inform_mutex);
 405           g_async_queue_lock (real->queue);
 406         }
 407       g_mutex_unlock (inform_mutex);
 408     }
 409
 410   if (g_async_queue_length_unlocked (real->queue) == -real->num_threads)
 411     {
 412       /* No thread is currently doing something (and nothing is left
 413        * to process in the queue) */
 414       if (real->num_threads == 0) /* No threads left, we clean up */
 415         {
 416           g_async_queue_unlock (real->queue);
 417           g_thread_pool_free_internal (real);
 418           return;
 419         }
 420
 421       g_thread_pool_wakeup_and_stop_all (real);
 422     }
 423
 424   real->waiting = FALSE; /* The last thread should cleanup the pool */
 425   g_async_queue_unlock (real->queue);
 426 }
 427
 428 static void
 429 g_thread_pool_free_internal (GRealThreadPool* pool)
 430 {
 431   g_return_if_fail (pool);
 432   g_return_if_fail (!pool->running);
 433   g_return_if_fail (pool->num_threads == 0);
 434
 435   g_async_queue_unref (pool->queue);
 436
 437   g_free (pool);
 438 }
 439
 440 static void
 441 g_thread_pool_wakeup_and_stop_all (GRealThreadPool* pool)
 442 {
 443   guint i;
 444
 445   g_return_if_fail (pool);
 446   g_return_if_fail (!pool->running);
 447   g_return_if_fail (pool->num_threads != 0);
 448   g_return_if_fail (g_async_queue_length_unlocked (pool->queue) ==
 449                     -pool->num_threads);
 450
 451   pool->immediate = TRUE;
 452   for (i = 0; i < pool->num_threads; i++)
 453     g_async_queue_push_unlocked (pool->queue, GUINT_TO_POINTER (1));
 454 }
 455
 456 void
 457 g_thread_pool_set_max_unused_threads (gint max_threads)
 458 {
 459   g_return_if_fail (max_threads >= -1);
 460
 461   G_LOCK (unused_threads);
 462
 463   max_unused_threads = max_threads;
 464
 465   if (max_unused_threads < unused_threads && max_unused_threads != -1)
 466     {
 467       guint close_down_num = unused_threads - max_unused_threads;
 468       GThreadPriority priority;
 469
 470       while (close_down_num > 0)
 471         {
 472           guint old_close_down_num = close_down_num;
 473           for (priority = G_THREAD_PRIORITY_LOW;
 474                priority < G_THREAD_PRIORITY_URGENT + 1 && close_down_num > 0;
 475                priority++)
 476             {
 477               GAsyncQueue *queue = unused_thread_queue[priority];
 478               g_async_queue_lock (queue);
 479
 480               if (g_async_queue_length_unlocked (queue) < 0)
 481                 {
 482                   g_async_queue_push_unlocked (queue,
 483                                                stop_this_thread_marker);
 484                   close_down_num--;
 485                 }
 486
 487               g_async_queue_unlock (queue);
 488             }
 489
 490           /* Just to make sure, there are no counting problems */
 491           g_assert (old_close_down_num != close_down_num);
 492         }
 493     }
 494
 495   G_UNLOCK (unused_threads);
 496 }
 497
 498 gint
 499 g_thread_pool_get_max_unused_threads (void)
 500 {
 501   gint retval;
 502
 503   G_LOCK (unused_threads);
 504   retval = max_unused_threads;
 505   G_UNLOCK (unused_threads);
 506
 507   return retval;
 508 }
 509
 510 guint g_thread_pool_get_num_unused_threads (void)
 511 {
 512   guint retval;
 513
 514   G_LOCK (unused_threads);
 515   retval = unused_threads;
 516   G_UNLOCK (unused_threads);
 517
 518   return retval;
 519 }
 520
 521 void g_thread_pool_stop_unused_threads (void)
 522 {
 523   guint oldval = g_thread_pool_get_max_unused_threads ();
 524   g_thread_pool_set_max_unused_threads (0);
 525   g_thread_pool_set_max_unused_threads (oldval);
 526 }