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
  69   g_async_queue_lock (pool->queue);
  70   while (TRUE)
  71     {
  72       gpointer task;
  73       gboolean goto_global_pool = !pool->pool.exclusive;
  74       gint len = g_async_queue_length_unlocked (pool->queue);
  75
  76       if (g_thread_should_run (pool, len))
  77         {
  78           task = g_async_queue_pop_unlocked (pool->queue);
  79
  80           if (pool->num_threads > pool->max_threads && pool->max_threads != -1)
  81             /* We are in fact a superfluous threads, so we go to the
  82              * global pool and just hand the data further to the next one
  83              * waiting in the queue */
  84             {
  85               g_async_queue_push_unlocked (pool->queue, task);
  86               goto_global_pool = TRUE;
  87             }
  88           else if (pool->running || !pool->immediate)
  89             {
  90               g_async_queue_unlock (pool->queue);
  91               pool->pool.thread_func (task, pool->pool.user_data);
  92               g_async_queue_lock (pool->queue);
  93             }
  94
  95           len = g_async_queue_length_unlocked (pool->queue);
  96         }
  97
  98       if (!g_thread_should_run (pool, len))
  99         g_cond_broadcast (inform_cond);
 100
 101       if (!pool->running && (pool->immediate || len <= 0))
 102         goto_global_pool = TRUE;
 103       else if (len >= 0)
 104         /* At this pool there is no thread waiting */
 105         goto_global_pool = FALSE;
 106
 107       if (goto_global_pool)
 108         {
 109           GThreadPriority priority = pool->pool.priority;
 110           pool->num_threads--;
 111
 112           if (!pool->running && !pool->waiting)
 113             {
 114               if (pool->num_threads == 0)
 115                 {
 116                   g_async_queue_unlock (pool->queue);
 117                   g_thread_pool_free_internal (pool);
 118                 }
 119               else if (len == - pool->num_threads)
 120                 g_thread_pool_wakeup_and_stop_all (pool);
 121             }
 122           else
 123             g_async_queue_unlock (pool->queue);
 124
 125           g_async_queue_lock (unused_thread_queue[priority]);
 126
 127           G_LOCK (unused_threads);
 128           if (unused_threads >= max_unused_threads)
 129             {
 130               G_UNLOCK (unused_threads);
 131               g_async_queue_unlock (unused_thread_queue[priority]);
 132               /* Stop this thread */
 133               return;
 134             }
 135           unused_threads++;
 136           G_UNLOCK (unused_threads);
 137
 138           pool =
 139             g_async_queue_pop_unlocked (unused_thread_queue[priority]);
 140
 141           G_LOCK (unused_threads);
 142           unused_threads--;
 143           G_UNLOCK (unused_threads);
 144
 145           g_async_queue_unlock (unused_thread_queue[priority]);
 146
 147           if (pool == stop_this_thread_marker)
 148             /* Stop this thread */
 149             return;
 150
 151           g_async_queue_lock (pool->queue);
 152
 153           /* pool->num_threads++ is not done here, but in
 154            * g_thread_pool_start_thread to make the new started thread
 155            * known to the pool, before itself can do it. */
 156         }
 157     }
 158 }
 159
 160 static void
 161 g_thread_pool_start_thread (GRealThreadPool  *pool,
 162                             GError          **error)
 163 {
 164   gboolean success = FALSE;
 165   GThreadPriority priority = pool->pool.priority;
 166   GAsyncQueue *queue = unused_thread_queue[priority];
 167
 168   if (pool->num_threads >= pool->max_threads && pool->max_threads != -1)
 169     /* Enough threads are already running */
 170     return;
 171
 172   g_async_queue_lock (queue);
 173
 174   if (g_async_queue_length_unlocked (queue) < 0)
 175     {
 176       /* First we try a thread with the right priority */
 177       g_async_queue_push_unlocked (queue, pool);
 178       success = TRUE;
 179     }
 180
 181   g_async_queue_unlock (queue);
 182
 183   /* We will not search for threads with other priorities, because changing
 184    * priority is quite unportable */
 185
 186   if (!success)
 187     {
 188       GError *local_error = NULL;
 189       /* No thread was found, we have to start one new */
 190       g_thread_create (g_thread_pool_thread_proxy, pool,
 191                        pool->pool.stack_size, FALSE,
 192                        pool->pool.bound, priority, &local_error);
 193
 194       if (local_error)
 195         {
 196           g_propagate_error (error, local_error);
 197           return;
 198         }
 199     }
 200
 201   /* See comment in g_thread_pool_thread_proxy as to why this is done
 202    * here and not there */
 203   pool->num_threads++;
 204 }
 205
 206 GThreadPool*
 207 g_thread_pool_new (GFunc            thread_func,
 208                    gint             max_threads,
 209                    gulong           stack_size,
 210                    gboolean         bound,
 211                    GThreadPriority  priority,
 212                    gboolean         exclusive,
 213                    gpointer         user_data,
 214                    GError         **error)
 215 {
 216   GRealThreadPool *retval;
 217
 218   g_return_val_if_fail (thread_func, NULL);
 219   g_return_val_if_fail (!exclusive || max_threads != -1, NULL);
 220   g_return_val_if_fail (max_threads >= -1, NULL);
 221   g_return_val_if_fail (g_thread_supported (), NULL);
 222
 223   retval = g_new (GRealThreadPool, 1);
 224
 225   retval->pool.thread_func = thread_func;
 226   retval->pool.stack_size = stack_size;
 227   retval->pool.bound = bound;
 228   retval->pool.priority = priority;
 229   retval->pool.exclusive = exclusive;
 230   retval->pool.user_data = user_data;
 231   retval->queue = g_async_queue_new ();
 232   retval->max_threads = max_threads;
 233   retval->num_threads = 0;
 234   retval->running = TRUE;
 235
 236   if (!inform_mutex)
 237     {
 238       inform_mutex = g_mutex_new ();
 239       inform_cond = g_cond_new ();
 240       for (priority = G_THREAD_PRIORITY_LOW;
 241            priority < G_THREAD_PRIORITY_URGENT + 1; priority++)
 242         unused_thread_queue[priority] = g_async_queue_new ();
 243     }
 244
 245   if (retval->pool.exclusive)
 246     {
 247       g_async_queue_lock (retval->queue);
 248
 249       while (retval->num_threads < retval->max_threads)
 250         {
 251           GError *local_error = NULL;
 252           g_thread_pool_start_thread (retval, &local_error);
 253           if (local_error)
 254             {
 255               g_propagate_error (error, local_error);
 256               break;
 257             }
 258         }
 259
 260       g_async_queue_unlock (retval->queue);
 261     }
 262
 263   return (GThreadPool*) retval;
 264 }
 265
 266 void
 267 g_thread_pool_push (GThreadPool     *pool,
 268                     gpointer         data,
 269                     GError         **error)
 270 {
 271   GRealThreadPool *real = (GRealThreadPool*) pool;
 272
 273   g_return_if_fail (real);
 274
 275   g_async_queue_lock (real->queue);
 276
 277   if (!real->running)
 278     {
 279       g_async_queue_unlock (real->queue);
 280       g_return_if_fail (real->running);
 281     }
 282
 283   if (!pool->exclusive && g_async_queue_length_unlocked (real->queue) >= 0)
 284     /* No thread is waiting in the queue */
 285     g_thread_pool_start_thread (real, error);
 286
 287   g_async_queue_push_unlocked (real->queue, data);
 288   g_async_queue_unlock (real->queue);
 289 }
 290
 291 void
 292 g_thread_pool_set_max_threads (GThreadPool     *pool,
 293                                gint             max_threads,
 294                                GError         **error)
 295 {
 296   GRealThreadPool *real = (GRealThreadPool*) pool;
 297   gint to_start;
 298
 299   g_return_if_fail (real);
 300   g_return_if_fail (real->running);
 301   g_return_if_fail (!real->pool.exclusive || max_threads != -1);
 302   g_return_if_fail (max_threads >= -1);
 303
 304   g_async_queue_lock (real->queue);
 305
 306   real->max_threads = max_threads;
 307
 308   if (pool->exclusive)
 309     to_start = real->max_threads - real->num_threads;
 310   else
 311     to_start = g_async_queue_length_unlocked (real->queue);
 312
 313   for ( ; to_start > 0; to_start--)
 314     {
 315       GError *local_error = NULL;
 316       g_thread_pool_start_thread (real, &local_error);
 317       if (local_error)
 318         {
 319           g_propagate_error (error, local_error);
 320           break;
 321         }
 322     }
 323
 324   g_async_queue_unlock (real->queue);
 325 }
 326
 327 gint
 328 g_thread_pool_get_max_threads (GThreadPool     *pool)
 329 {
 330   GRealThreadPool *real = (GRealThreadPool*) pool;
 331   gint retval;
 332
 333   g_return_val_if_fail (real, 0);
 334   g_return_val_if_fail (real->running, 0);
 335
 336   g_async_queue_lock (real->queue);
 337
 338   retval = real->max_threads;
 339
 340   g_async_queue_unlock (real->queue);
 341
 342   return retval;
 343 }
 344
 345 guint
 346 g_thread_pool_get_num_threads (GThreadPool     *pool)
 347 {
 348   GRealThreadPool *real = (GRealThreadPool*) pool;
 349   guint retval;
 350
 351   g_return_val_if_fail (real, 0);
 352   g_return_val_if_fail (real->running, 0);
 353
 354   g_async_queue_lock (real->queue);
 355
 356   retval = real->num_threads;
 357
 358   g_async_queue_unlock (real->queue);
 359
 360   return retval;
 361 }
 362
 363 guint
 364 g_thread_pool_unprocessed (GThreadPool     *pool)
 365 {
 366   GRealThreadPool *real = (GRealThreadPool*) pool;
 367   gint unprocessed;
 368
 369   g_return_val_if_fail (real, 0);
 370   g_return_val_if_fail (real->running, 0);
 371
 372   unprocessed = g_async_queue_length (real->queue);
 373
 374   return MAX (unprocessed, 0);
 375 }
 376
 377 void
 378 g_thread_pool_free (GThreadPool     *pool,
 379                     gboolean         immediate,
 380                     gboolean         wait)
 381 {
 382   GRealThreadPool *real = (GRealThreadPool*) pool;
 383
 384   g_return_if_fail (real);
 385   g_return_if_fail (real->running);
 386   /* It there's no thread allowed here, there is not much sense in
 387    * not stopping this pool immediatly, when it's not empty */
 388   g_return_if_fail (immediate || real->max_threads != 0 ||
 389                     g_async_queue_length (real->queue) == 0);
 390
 391   g_async_queue_lock (real->queue);
 392
 393   real->running = FALSE;
 394   real->immediate = immediate;
 395   real->waiting = wait;
 396
 397   if (wait)
 398     {
 399       g_mutex_lock (inform_mutex);
 400       while (g_async_queue_length_unlocked (real->queue) != -real->num_threads)
 401         {
 402           g_async_queue_unlock (real->queue);
 403           g_cond_wait (inform_cond, inform_mutex);
 404           g_async_queue_lock (real->queue);
 405         }
 406       g_mutex_unlock (inform_mutex);
 407     }
 408
 409   if (g_async_queue_length_unlocked (real->queue) == -real->num_threads)
 410     {
 411       /* No thread is currently doing something (and nothing is left
 412        * to process in the queue) */
 413       if (real->num_threads == 0) /* No threads left, we clean up */
 414         {
 415           g_async_queue_unlock (real->queue);
 416           g_thread_pool_free_internal (real);
 417           return;
 418         }
 419
 420       g_thread_pool_wakeup_and_stop_all (real);
 421     }
 422
 423   real->waiting = FALSE; /* The last thread should cleanup the pool */
 424   g_async_queue_unlock (real->queue);
 425 }
 426
 427 static void
 428 g_thread_pool_free_internal (GRealThreadPool* pool)
 429 {
 430   g_return_if_fail (pool);
 431   g_return_if_fail (!pool->running);
 432   g_return_if_fail (pool->num_threads == 0);
 433
 434   g_async_queue_unref (pool->queue);
 435
 436   g_free (pool);
 437 }
 438
 439 static void
 440 g_thread_pool_wakeup_and_stop_all (GRealThreadPool* pool)
 441 {
 442   guint i;
 443
 444   g_return_if_fail (pool);
 445   g_return_if_fail (!pool->running);
 446   g_return_if_fail (pool->num_threads != 0);
 447   g_return_if_fail (g_async_queue_length_unlocked (pool->queue) ==
 448                     -pool->num_threads);
 449
 450   pool->immediate = TRUE;
 451   for (i = 0; i < pool->num_threads; i++)
 452     g_async_queue_push_unlocked (pool->queue, GUINT_TO_POINTER (1));
 453 }
 454
 455 void
 456 g_thread_pool_set_max_unused_threads (gint max_threads)
 457 {
 458   g_return_if_fail (max_threads >= -1);
 459
 460   G_LOCK (unused_threads);
 461
 462   max_unused_threads = max_threads;
 463
 464   if (max_unused_threads < unused_threads && max_unused_threads != -1)
 465     {
 466       guint close_down_num = unused_threads - max_unused_threads;
 467       GThreadPriority priority;
 468
 469       while (close_down_num > 0)
 470         {
 471           guint old_close_down_num = close_down_num;
 472           for (priority = G_THREAD_PRIORITY_LOW;
 473                priority < G_THREAD_PRIORITY_URGENT + 1 && close_down_num > 0;
 474                priority++)
 475             {
 476               GAsyncQueue *queue = unused_thread_queue[priority];
 477               g_async_queue_lock (queue);
 478
 479               if (g_async_queue_length_unlocked (queue) < 0)
 480                 {
 481                   g_async_queue_push_unlocked (queue,
 482                                                stop_this_thread_marker);
 483                   close_down_num--;
 484                 }
 485
 486               g_async_queue_unlock (queue);
 487             }
 488
 489           /* Just to make sure, there are no counting problems */
 490           g_assert (old_close_down_num != close_down_num);
 491         }
 492     }
 493
 494   G_UNLOCK (unused_threads);
 495 }
 496
 497 gint
 498 g_thread_pool_get_max_unused_threads (void)
 499 {
 500   gint retval;
 501
 502   G_LOCK (unused_threads);
 503   retval = max_unused_threads;
 504   G_UNLOCK (unused_threads);
 505
 506   return retval;
 507 }
 508
 509 guint g_thread_pool_get_num_unused_threads (void)
 510 {
 511   guint retval;
 512
 513   G_LOCK (unused_threads);
 514   retval = unused_threads;
 515   G_UNLOCK (unused_threads);
 516
 517   return retval;
 518 }
 519
 520 void g_thread_pool_stop_unused_threads (void)
 521 {
 522   guint oldval = g_thread_pool_get_max_unused_threads ();
 523   g_thread_pool_set_max_unused_threads (0);
 524   g_thread_pool_set_max_unused_threads (oldval);
 525 }