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1 office 1 /* GLIB - Library of useful routines for C programming
2 * Copyright (C) 1995-1997 Peter Mattis, Spencer Kimball and Josh MacDonald
3 *
4 * GThreadPool: 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, see <http://www.gnu.org/licenses/>.
19 */
20  
21 /*
22 * MT safe
23 */
24  
25 #include "config.h"
26  
27 #include "gthreadpool.h"
28  
29 #include "gasyncqueue.h"
30 #include "gasyncqueueprivate.h"
31 #include "gmain.h"
32 #include "gtestutils.h"
33 #include "gtimer.h"
34  
35 /**
36 * SECTION:thread_pools
37 * @title: Thread Pools
38 * @short_description: pools of threads to execute work concurrently
39 * @see_also: #GThread
40 *
41 * Sometimes you wish to asynchronously fork out the execution of work
42 * and continue working in your own thread. If that will happen often,
43 * the overhead of starting and destroying a thread each time might be
44 * too high. In such cases reusing already started threads seems like a
45 * good idea. And it indeed is, but implementing this can be tedious
46 * and error-prone.
47 *
48 * Therefore GLib provides thread pools for your convenience. An added
49 * advantage is, that the threads can be shared between the different
50 * subsystems of your program, when they are using GLib.
51 *
52 * To create a new thread pool, you use g_thread_pool_new().
53 * It is destroyed by g_thread_pool_free().
54 *
55 * If you want to execute a certain task within a thread pool,
56 * you call g_thread_pool_push().
57 *
58 * To get the current number of running threads you call
59 * g_thread_pool_get_num_threads(). To get the number of still
60 * unprocessed tasks you call g_thread_pool_unprocessed(). To control
61 * the maximal number of threads for a thread pool, you use
62 * g_thread_pool_get_max_threads() and g_thread_pool_set_max_threads().
63 *
64 * Finally you can control the number of unused threads, that are kept
65 * alive by GLib for future use. The current number can be fetched with
66 * g_thread_pool_get_num_unused_threads(). The maximal number can be
67 * controlled by g_thread_pool_get_max_unused_threads() and
68 * g_thread_pool_set_max_unused_threads(). All currently unused threads
69 * can be stopped by calling g_thread_pool_stop_unused_threads().
70 */
71  
72 #define DEBUG_MSG(x)
73 /* #define DEBUG_MSG(args) g_printerr args ; g_printerr ("\n"); */
74  
75 typedef struct _GRealThreadPool GRealThreadPool;
76  
77 /**
78 * GThreadPool:
79 * @func: the function to execute in the threads of this pool
80 * @user_data: the user data for the threads of this pool
81 * @exclusive: are all threads exclusive to this pool
82 *
83 * The #GThreadPool struct represents a thread pool. It has three
84 * public read-only members, but the underlying struct is bigger,
85 * so you must not copy this struct.
86 */
87 struct _GRealThreadPool
88 {
89 GThreadPool pool;
90 GAsyncQueue *queue;
91 GCond cond;
92 gint max_threads;
93 gint num_threads;
94 gboolean running;
95 gboolean immediate;
96 gboolean waiting;
97 GCompareDataFunc sort_func;
98 gpointer sort_user_data;
99 };
100  
101 /* The following is just an address to mark the wakeup order for a
102 * thread, it could be any address (as long, as it isn't a valid
103 * GThreadPool address)
104 */
105 static const gpointer wakeup_thread_marker = (gpointer) &g_thread_pool_new;
106 static gint wakeup_thread_serial = 0;
107  
108 /* Here all unused threads are waiting */
109 static GAsyncQueue *unused_thread_queue = NULL;
110 static gint unused_threads = 0;
111 static gint max_unused_threads = 2;
112 static gint kill_unused_threads = 0;
113 static guint max_idle_time = 15 * 1000;
114  
115 static void g_thread_pool_queue_push_unlocked (GRealThreadPool *pool,
116 gpointer data);
117 static void g_thread_pool_free_internal (GRealThreadPool *pool);
118 static gpointer g_thread_pool_thread_proxy (gpointer data);
119 static gboolean g_thread_pool_start_thread (GRealThreadPool *pool,
120 GError **error);
121 static void g_thread_pool_wakeup_and_stop_all (GRealThreadPool *pool);
122 static GRealThreadPool* g_thread_pool_wait_for_new_pool (void);
123 static gpointer g_thread_pool_wait_for_new_task (GRealThreadPool *pool);
124  
125 static void
126 g_thread_pool_queue_push_unlocked (GRealThreadPool *pool,
127 gpointer data)
128 {
129 if (pool->sort_func)
130 g_async_queue_push_sorted_unlocked (pool->queue,
131 data,
132 pool->sort_func,
133 pool->sort_user_data);
134 else
135 g_async_queue_push_unlocked (pool->queue, data);
136 }
137  
138 static GRealThreadPool*
139 g_thread_pool_wait_for_new_pool (void)
140 {
141 GRealThreadPool *pool;
142 gint local_wakeup_thread_serial;
143 guint local_max_unused_threads;
144 gint local_max_idle_time;
145 gint last_wakeup_thread_serial;
146 gboolean have_relayed_thread_marker = FALSE;
147  
148 local_max_unused_threads = g_atomic_int_get (&max_unused_threads);
149 local_max_idle_time = g_atomic_int_get (&max_idle_time);
150 last_wakeup_thread_serial = g_atomic_int_get (&wakeup_thread_serial);
151  
152 g_atomic_int_inc (&unused_threads);
153  
154 do
155 {
156 if (g_atomic_int_get (&unused_threads) >= local_max_unused_threads)
157 {
158 /* If this is a superfluous thread, stop it. */
159 pool = NULL;
160 }
161 else if (local_max_idle_time > 0)
162 {
163 /* If a maximal idle time is given, wait for the given time. */
164 DEBUG_MSG (("thread %p waiting in global pool for %f seconds.",
165 g_thread_self (), local_max_idle_time / 1000.0));
166  
167 pool = g_async_queue_timeout_pop (unused_thread_queue,
168 local_max_idle_time * 1000);
169 }
170 else
171 {
172 /* If no maximal idle time is given, wait indefinitely. */
173 DEBUG_MSG (("thread %p waiting in global pool.", g_thread_self ()));
174 pool = g_async_queue_pop (unused_thread_queue);
175 }
176  
177 if (pool == wakeup_thread_marker)
178 {
179 local_wakeup_thread_serial = g_atomic_int_get (&wakeup_thread_serial);
180 if (last_wakeup_thread_serial == local_wakeup_thread_serial)
181 {
182 if (!have_relayed_thread_marker)
183 {
184 /* If this wakeup marker has been received for
185 * the second time, relay it.
186 */
187 DEBUG_MSG (("thread %p relaying wakeup message to "
188 "waiting thread with lower serial.",
189 g_thread_self ()));
190  
191 g_async_queue_push (unused_thread_queue, wakeup_thread_marker);
192 have_relayed_thread_marker = TRUE;
193  
194 /* If a wakeup marker has been relayed, this thread
195 * will get out of the way for 100 microseconds to
196 * avoid receiving this marker again.
197 */
198 g_usleep (100);
199 }
200 }
201 else
202 {
203 if (g_atomic_int_add (&kill_unused_threads, -1) > 0)
204 {
205 pool = NULL;
206 break;
207 }
208  
209 DEBUG_MSG (("thread %p updating to new limits.",
210 g_thread_self ()));
211  
212 local_max_unused_threads = g_atomic_int_get (&max_unused_threads);
213 local_max_idle_time = g_atomic_int_get (&max_idle_time);
214 last_wakeup_thread_serial = local_wakeup_thread_serial;
215  
216 have_relayed_thread_marker = FALSE;
217 }
218 }
219 }
220 while (pool == wakeup_thread_marker);
221  
222 g_atomic_int_add (&unused_threads, -1);
223  
224 return pool;
225 }
226  
227 static gpointer
228 g_thread_pool_wait_for_new_task (GRealThreadPool *pool)
229 {
230 gpointer task = NULL;
231  
232 if (pool->running || (!pool->immediate &&
233 g_async_queue_length_unlocked (pool->queue) > 0))
234 {
235 /* This thread pool is still active. */
236 if (pool->num_threads > pool->max_threads && pool->max_threads != -1)
237 {
238 /* This is a superfluous thread, so it goes to the global pool. */
239 DEBUG_MSG (("superfluous thread %p in pool %p.",
240 g_thread_self (), pool));
241 }
242 else if (pool->pool.exclusive)
243 {
244 /* Exclusive threads stay attached to the pool. */
245 task = g_async_queue_pop_unlocked (pool->queue);
246  
247 DEBUG_MSG (("thread %p in exclusive pool %p waits for task "
248 "(%d running, %d unprocessed).",
249 g_thread_self (), pool, pool->num_threads,
250 g_async_queue_length_unlocked (pool->queue)));
251 }
252 else
253 {
254 /* A thread will wait for new tasks for at most 1/2
255 * second before going to the global pool.
256 */
257 DEBUG_MSG (("thread %p in pool %p waits for up to a 1/2 second for task "
258 "(%d running, %d unprocessed).",
259 g_thread_self (), pool, pool->num_threads,
260 g_async_queue_length_unlocked (pool->queue)));
261  
262 task = g_async_queue_timeout_pop_unlocked (pool->queue,
263 G_USEC_PER_SEC / 2);
264 }
265 }
266 else
267 {
268 /* This thread pool is inactive, it will no longer process tasks. */
269 DEBUG_MSG (("pool %p not active, thread %p will go to global pool "
270 "(running: %s, immediate: %s, len: %d).",
271 pool, g_thread_self (),
272 pool->running ? "true" : "false",
273 pool->immediate ? "true" : "false",
274 g_async_queue_length_unlocked (pool->queue)));
275 }
276  
277 return task;
278 }
279  
280  
281 static gpointer
282 g_thread_pool_thread_proxy (gpointer data)
283 {
284 GRealThreadPool *pool;
285  
286 pool = data;
287  
288 DEBUG_MSG (("thread %p started for pool %p.", g_thread_self (), pool));
289  
290 g_async_queue_lock (pool->queue);
291  
292 while (TRUE)
293 {
294 gpointer task;
295  
296 task = g_thread_pool_wait_for_new_task (pool);
297 if (task)
298 {
299 if (pool->running || !pool->immediate)
300 {
301 /* A task was received and the thread pool is active,
302 * so execute the function.
303 */
304 g_async_queue_unlock (pool->queue);
305 DEBUG_MSG (("thread %p in pool %p calling func.",
306 g_thread_self (), pool));
307 pool->pool.func (task, pool->pool.user_data);
308 g_async_queue_lock (pool->queue);
309 }
310 }
311 else
312 {
313 /* No task was received, so this thread goes to the global pool. */
314 gboolean free_pool = FALSE;
315  
316 DEBUG_MSG (("thread %p leaving pool %p for global pool.",
317 g_thread_self (), pool));
318 pool->num_threads--;
319  
320 if (!pool->running)
321 {
322 if (!pool->waiting)
323 {
324 if (pool->num_threads == 0)
325 {
326 /* If the pool is not running and no other
327 * thread is waiting for this thread pool to
328 * finish and this is the last thread of this
329 * pool, free the pool.
330 */
331 free_pool = TRUE;
332 }
333 else
334 {
335 /* If the pool is not running and no other
336 * thread is waiting for this thread pool to
337 * finish and this is not the last thread of
338 * this pool and there are no tasks left in the
339 * queue, wakeup the remaining threads.
340 */
341 if (g_async_queue_length_unlocked (pool->queue) ==
342 - pool->num_threads)
343 g_thread_pool_wakeup_and_stop_all (pool);
344 }
345 }
346 else if (pool->immediate ||
347 g_async_queue_length_unlocked (pool->queue) <= 0)
348 {
349 /* If the pool is not running and another thread is
350 * waiting for this thread pool to finish and there
351 * are either no tasks left or the pool shall stop
352 * immediately, inform the waiting thread of a change
353 * of the thread pool state.
354 */
355 g_cond_broadcast (&pool->cond);
356 }
357 }
358  
359 g_async_queue_unlock (pool->queue);
360  
361 if (free_pool)
362 g_thread_pool_free_internal (pool);
363  
364 if ((pool = g_thread_pool_wait_for_new_pool ()) == NULL)
365 break;
366  
367 g_async_queue_lock (pool->queue);
368  
369 DEBUG_MSG (("thread %p entering pool %p from global pool.",
370 g_thread_self (), pool));
371  
372 /* pool->num_threads++ is not done here, but in
373 * g_thread_pool_start_thread to make the new started
374 * thread known to the pool before itself can do it.
375 */
376 }
377 }
378  
379 return NULL;
380 }
381  
382 static gboolean
383 g_thread_pool_start_thread (GRealThreadPool *pool,
384 GError **error)
385 {
386 gboolean success = FALSE;
387  
388 if (pool->num_threads >= pool->max_threads && pool->max_threads != -1)
389 /* Enough threads are already running */
390 return TRUE;
391  
392 g_async_queue_lock (unused_thread_queue);
393  
394 if (g_async_queue_length_unlocked (unused_thread_queue) < 0)
395 {
396 g_async_queue_push_unlocked (unused_thread_queue, pool);
397 success = TRUE;
398 }
399  
400 g_async_queue_unlock (unused_thread_queue);
401  
402 if (!success)
403 {
404 GThread *thread;
405  
406 /* No thread was found, we have to start a new one */
407 thread = g_thread_try_new ("pool", g_thread_pool_thread_proxy, pool, error);
408  
409 if (thread == NULL)
410 return FALSE;
411  
412 g_thread_unref (thread);
413 }
414  
415 /* See comment in g_thread_pool_thread_proxy as to why this is done
416 * here and not there
417 */
418 pool->num_threads++;
419  
420 return TRUE;
421 }
422  
423 /**
424 * g_thread_pool_new:
425 * @func: a function to execute in the threads of the new thread pool
426 * @user_data: user data that is handed over to @func every time it
427 * is called
428 * @max_threads: the maximal number of threads to execute concurrently
429 * in the new thread pool, -1 means no limit
430 * @exclusive: should this thread pool be exclusive?
431 * @error: return location for error, or %NULL
432 *
433 * This function creates a new thread pool.
434 *
435 * Whenever you call g_thread_pool_push(), either a new thread is
436 * created or an unused one is reused. At most @max_threads threads
437 * are running concurrently for this thread pool. @max_threads = -1
438 * allows unlimited threads to be created for this thread pool. The
439 * newly created or reused thread now executes the function @func
440 * with the two arguments. The first one is the parameter to
441 * g_thread_pool_push() and the second one is @user_data.
442 *
443 * The parameter @exclusive determines whether the thread pool owns
444 * all threads exclusive or shares them with other thread pools.
445 * If @exclusive is %TRUE, @max_threads threads are started
446 * immediately and they will run exclusively for this thread pool
447 * until it is destroyed by g_thread_pool_free(). If @exclusive is
448 * %FALSE, threads are created when needed and shared between all
449 * non-exclusive thread pools. This implies that @max_threads may
450 * not be -1 for exclusive thread pools. Besides, exclusive thread
451 * pools are not affected by g_thread_pool_set_max_idle_time()
452 * since their threads are never considered idle and returned to the
453 * global pool.
454 *
455 * @error can be %NULL to ignore errors, or non-%NULL to report
456 * errors. An error can only occur when @exclusive is set to %TRUE
457 * and not all @max_threads threads could be created.
458 * See #GThreadError for possible errors that may occur.
459 * Note, even in case of error a valid #GThreadPool is returned.
460 *
461 * Returns: the new #GThreadPool
462 */
463 GThreadPool *
464 g_thread_pool_new (GFunc func,
465 gpointer user_data,
466 gint max_threads,
467 gboolean exclusive,
468 GError **error)
469 {
470 GRealThreadPool *retval;
471 G_LOCK_DEFINE_STATIC (init);
472  
473 g_return_val_if_fail (func, NULL);
474 g_return_val_if_fail (!exclusive || max_threads != -1, NULL);
475 g_return_val_if_fail (max_threads >= -1, NULL);
476  
477 retval = g_new (GRealThreadPool, 1);
478  
479 retval->pool.func = func;
480 retval->pool.user_data = user_data;
481 retval->pool.exclusive = exclusive;
482 retval->queue = g_async_queue_new ();
483 g_cond_init (&retval->cond);
484 retval->max_threads = max_threads;
485 retval->num_threads = 0;
486 retval->running = TRUE;
487 retval->immediate = FALSE;
488 retval->waiting = FALSE;
489 retval->sort_func = NULL;
490 retval->sort_user_data = NULL;
491  
492 G_LOCK (init);
493 if (!unused_thread_queue)
494 unused_thread_queue = g_async_queue_new ();
495 G_UNLOCK (init);
496  
497 if (retval->pool.exclusive)
498 {
499 g_async_queue_lock (retval->queue);
500  
501 while (retval->num_threads < retval->max_threads)
502 {
503 GError *local_error = NULL;
504  
505 if (!g_thread_pool_start_thread (retval, &local_error))
506 {
507 g_propagate_error (error, local_error);
508 break;
509 }
510 }
511  
512 g_async_queue_unlock (retval->queue);
513 }
514  
515 return (GThreadPool*) retval;
516 }
517  
518 /**
519 * g_thread_pool_push:
520 * @pool: a #GThreadPool
521 * @data: a new task for @pool
522 * @error: return location for error, or %NULL
523 *
524 * Inserts @data into the list of tasks to be executed by @pool.
525 *
526 * When the number of currently running threads is lower than the
527 * maximal allowed number of threads, a new thread is started (or
528 * reused) with the properties given to g_thread_pool_new().
529 * Otherwise, @data stays in the queue until a thread in this pool
530 * finishes its previous task and processes @data.
531 *
532 * @error can be %NULL to ignore errors, or non-%NULL to report
533 * errors. An error can only occur when a new thread couldn't be
534 * created. In that case @data is simply appended to the queue of
535 * work to do.
536 *
537 * Before version 2.32, this function did not return a success status.
538 *
539 * Returns: %TRUE on success, %FALSE if an error occurred
540 */
541 gboolean
542 g_thread_pool_push (GThreadPool *pool,
543 gpointer data,
544 GError **error)
545 {
546 GRealThreadPool *real;
547 gboolean result;
548  
549 real = (GRealThreadPool*) pool;
550  
551 g_return_val_if_fail (real, FALSE);
552 g_return_val_if_fail (real->running, FALSE);
553  
554 result = TRUE;
555  
556 g_async_queue_lock (real->queue);
557  
558 if (g_async_queue_length_unlocked (real->queue) >= 0)
559 {
560 /* No thread is waiting in the queue */
561 GError *local_error = NULL;
562  
563 if (!g_thread_pool_start_thread (real, &local_error))
564 {
565 g_propagate_error (error, local_error);
566 result = FALSE;
567 }
568 }
569  
570 g_thread_pool_queue_push_unlocked (real, data);
571 g_async_queue_unlock (real->queue);
572  
573 return result;
574 }
575  
576 /**
577 * g_thread_pool_set_max_threads:
578 * @pool: a #GThreadPool
579 * @max_threads: a new maximal number of threads for @pool,
580 * or -1 for unlimited
581 * @error: return location for error, or %NULL
582 *
583 * Sets the maximal allowed number of threads for @pool.
584 * A value of -1 means that the maximal number of threads
585 * is unlimited. If @pool is an exclusive thread pool, setting
586 * the maximal number of threads to -1 is not allowed.
587 *
588 * Setting @max_threads to 0 means stopping all work for @pool.
589 * It is effectively frozen until @max_threads is set to a non-zero
590 * value again.
591 *
592 * A thread is never terminated while calling @func, as supplied by
593 * g_thread_pool_new(). Instead the maximal number of threads only
594 * has effect for the allocation of new threads in g_thread_pool_push().
595 * A new thread is allocated, whenever the number of currently
596 * running threads in @pool is smaller than the maximal number.
597 *
598 * @error can be %NULL to ignore errors, or non-%NULL to report
599 * errors. An error can only occur when a new thread couldn't be
600 * created.
601 *
602 * Before version 2.32, this function did not return a success status.
603 *
604 * Returns: %TRUE on success, %FALSE if an error occurred
605 */
606 gboolean
607 g_thread_pool_set_max_threads (GThreadPool *pool,
608 gint max_threads,
609 GError **error)
610 {
611 GRealThreadPool *real;
612 gint to_start;
613 gboolean result;
614  
615 real = (GRealThreadPool*) pool;
616  
617 g_return_val_if_fail (real, FALSE);
618 g_return_val_if_fail (real->running, FALSE);
619 g_return_val_if_fail (!real->pool.exclusive || max_threads != -1, FALSE);
620 g_return_val_if_fail (max_threads >= -1, FALSE);
621  
622 result = TRUE;
623  
624 g_async_queue_lock (real->queue);
625  
626 real->max_threads = max_threads;
627  
628 if (pool->exclusive)
629 to_start = real->max_threads - real->num_threads;
630 else
631 to_start = g_async_queue_length_unlocked (real->queue);
632  
633 for ( ; to_start > 0; to_start--)
634 {
635 GError *local_error = NULL;
636  
637 if (!g_thread_pool_start_thread (real, &local_error))
638 {
639 g_propagate_error (error, local_error);
640 result = FALSE;
641 break;
642 }
643 }
644  
645 g_async_queue_unlock (real->queue);
646  
647 return result;
648 }
649  
650 /**
651 * g_thread_pool_get_max_threads:
652 * @pool: a #GThreadPool
653 *
654 * Returns the maximal number of threads for @pool.
655 *
656 * Returns: the maximal number of threads
657 */
658 gint
659 g_thread_pool_get_max_threads (GThreadPool *pool)
660 {
661 GRealThreadPool *real;
662 gint retval;
663  
664 real = (GRealThreadPool*) pool;
665  
666 g_return_val_if_fail (real, 0);
667 g_return_val_if_fail (real->running, 0);
668  
669 g_async_queue_lock (real->queue);
670 retval = real->max_threads;
671 g_async_queue_unlock (real->queue);
672  
673 return retval;
674 }
675  
676 /**
677 * g_thread_pool_get_num_threads:
678 * @pool: a #GThreadPool
679 *
680 * Returns the number of threads currently running in @pool.
681 *
682 * Returns: the number of threads currently running
683 */
684 guint
685 g_thread_pool_get_num_threads (GThreadPool *pool)
686 {
687 GRealThreadPool *real;
688 guint retval;
689  
690 real = (GRealThreadPool*) pool;
691  
692 g_return_val_if_fail (real, 0);
693 g_return_val_if_fail (real->running, 0);
694  
695 g_async_queue_lock (real->queue);
696 retval = real->num_threads;
697 g_async_queue_unlock (real->queue);
698  
699 return retval;
700 }
701  
702 /**
703 * g_thread_pool_unprocessed:
704 * @pool: a #GThreadPool
705 *
706 * Returns the number of tasks still unprocessed in @pool.
707 *
708 * Returns: the number of unprocessed tasks
709 */
710 guint
711 g_thread_pool_unprocessed (GThreadPool *pool)
712 {
713 GRealThreadPool *real;
714 gint unprocessed;
715  
716 real = (GRealThreadPool*) pool;
717  
718 g_return_val_if_fail (real, 0);
719 g_return_val_if_fail (real->running, 0);
720  
721 unprocessed = g_async_queue_length (real->queue);
722  
723 return MAX (unprocessed, 0);
724 }
725  
726 /**
727 * g_thread_pool_free:
728 * @pool: a #GThreadPool
729 * @immediate: should @pool shut down immediately?
730 * @wait_: should the function wait for all tasks to be finished?
731 *
732 * Frees all resources allocated for @pool.
733 *
734 * If @immediate is %TRUE, no new task is processed for @pool.
735 * Otherwise @pool is not freed before the last task is processed.
736 * Note however, that no thread of this pool is interrupted while
737 * processing a task. Instead at least all still running threads
738 * can finish their tasks before the @pool is freed.
739 *
740 * If @wait_ is %TRUE, the functions does not return before all
741 * tasks to be processed (dependent on @immediate, whether all
742 * or only the currently running) are ready.
743 * Otherwise the function returns immediately.
744 *
745 * After calling this function @pool must not be used anymore.
746 */
747 void
748 g_thread_pool_free (GThreadPool *pool,
749 gboolean immediate,
750 gboolean wait_)
751 {
752 GRealThreadPool *real;
753  
754 real = (GRealThreadPool*) pool;
755  
756 g_return_if_fail (real);
757 g_return_if_fail (real->running);
758  
759 /* If there's no thread allowed here, there is not much sense in
760 * not stopping this pool immediately, when it's not empty
761 */
762 g_return_if_fail (immediate ||
763 real->max_threads != 0 ||
764 g_async_queue_length (real->queue) == 0);
765  
766 g_async_queue_lock (real->queue);
767  
768 real->running = FALSE;
769 real->immediate = immediate;
770 real->waiting = wait_;
771  
772 if (wait_)
773 {
774 while (g_async_queue_length_unlocked (real->queue) != -real->num_threads &&
775 !(immediate && real->num_threads == 0))
776 g_cond_wait (&real->cond, _g_async_queue_get_mutex (real->queue));
777 }
778  
779 if (immediate || g_async_queue_length_unlocked (real->queue) == -real->num_threads)
780 {
781 /* No thread is currently doing something (and nothing is left
782 * to process in the queue)
783 */
784 if (real->num_threads == 0)
785 {
786 /* No threads left, we clean up */
787 g_async_queue_unlock (real->queue);
788 g_thread_pool_free_internal (real);
789 return;
790 }
791  
792 g_thread_pool_wakeup_and_stop_all (real);
793 }
794  
795 /* The last thread should cleanup the pool */
796 real->waiting = FALSE;
797 g_async_queue_unlock (real->queue);
798 }
799  
800 static void
801 g_thread_pool_free_internal (GRealThreadPool* pool)
802 {
803 g_return_if_fail (pool);
804 g_return_if_fail (pool->running == FALSE);
805 g_return_if_fail (pool->num_threads == 0);
806  
807 g_async_queue_unref (pool->queue);
808 g_cond_clear (&pool->cond);
809  
810 g_free (pool);
811 }
812  
813 static void
814 g_thread_pool_wakeup_and_stop_all (GRealThreadPool *pool)
815 {
816 guint i;
817  
818 g_return_if_fail (pool);
819 g_return_if_fail (pool->running == FALSE);
820 g_return_if_fail (pool->num_threads != 0);
821  
822 pool->immediate = TRUE;
823  
824 /*
825 * So here we're sending bogus data to the pool threads, which
826 * should cause them each to wake up, and check the above
827 * pool->immediate condition. However we don't want that
828 * data to be sorted (since it'll crash the sorter).
829 */
830 for (i = 0; i < pool->num_threads; i++)
831 g_async_queue_push_unlocked (pool->queue, GUINT_TO_POINTER (1));
832 }
833  
834 /**
835 * g_thread_pool_set_max_unused_threads:
836 * @max_threads: maximal number of unused threads
837 *
838 * Sets the maximal number of unused threads to @max_threads.
839 * If @max_threads is -1, no limit is imposed on the number
840 * of unused threads.
841 *
842 * The default value is 2.
843 */
844 void
845 g_thread_pool_set_max_unused_threads (gint max_threads)
846 {
847 g_return_if_fail (max_threads >= -1);
848  
849 g_atomic_int_set (&max_unused_threads, max_threads);
850  
851 if (max_threads != -1)
852 {
853 max_threads -= g_atomic_int_get (&unused_threads);
854 if (max_threads < 0)
855 {
856 g_atomic_int_set (&kill_unused_threads, -max_threads);
857 g_atomic_int_inc (&wakeup_thread_serial);
858  
859 g_async_queue_lock (unused_thread_queue);
860  
861 do
862 {
863 g_async_queue_push_unlocked (unused_thread_queue,
864 wakeup_thread_marker);
865 }
866 while (++max_threads);
867  
868 g_async_queue_unlock (unused_thread_queue);
869 }
870 }
871 }
872  
873 /**
874 * g_thread_pool_get_max_unused_threads:
875 *
876 * Returns the maximal allowed number of unused threads.
877 *
878 * Returns: the maximal number of unused threads
879 */
880 gint
881 g_thread_pool_get_max_unused_threads (void)
882 {
883 return g_atomic_int_get (&max_unused_threads);
884 }
885  
886 /**
887 * g_thread_pool_get_num_unused_threads:
888 *
889 * Returns the number of currently unused threads.
890 *
891 * Returns: the number of currently unused threads
892 */
893 guint
894 g_thread_pool_get_num_unused_threads (void)
895 {
896 return g_atomic_int_get (&unused_threads);
897 }
898  
899 /**
900 * g_thread_pool_stop_unused_threads:
901 *
902 * Stops all currently unused threads. This does not change the
903 * maximal number of unused threads. This function can be used to
904 * regularly stop all unused threads e.g. from g_timeout_add().
905 */
906 void
907 g_thread_pool_stop_unused_threads (void)
908 {
909 guint oldval;
910  
911 oldval = g_thread_pool_get_max_unused_threads ();
912  
913 g_thread_pool_set_max_unused_threads (0);
914 g_thread_pool_set_max_unused_threads (oldval);
915 }
916  
917 /**
918 * g_thread_pool_set_sort_function:
919 * @pool: a #GThreadPool
920 * @func: the #GCompareDataFunc used to sort the list of tasks.
921 * This function is passed two tasks. It should return
922 * 0 if the order in which they are handled does not matter,
923 * a negative value if the first task should be processed before
924 * the second or a positive value if the second task should be
925 * processed first.
926 * @user_data: user data passed to @func
927 *
928 * Sets the function used to sort the list of tasks. This allows the
929 * tasks to be processed by a priority determined by @func, and not
930 * just in the order in which they were added to the pool.
931 *
932 * Note, if the maximum number of threads is more than 1, the order
933 * that threads are executed cannot be guaranteed 100%. Threads are
934 * scheduled by the operating system and are executed at random. It
935 * cannot be assumed that threads are executed in the order they are
936 * created.
937 *
938 * Since: 2.10
939 */
940 void
941 g_thread_pool_set_sort_function (GThreadPool *pool,
942 GCompareDataFunc func,
943 gpointer user_data)
944 {
945 GRealThreadPool *real;
946  
947 real = (GRealThreadPool*) pool;
948  
949 g_return_if_fail (real);
950 g_return_if_fail (real->running);
951  
952 g_async_queue_lock (real->queue);
953  
954 real->sort_func = func;
955 real->sort_user_data = user_data;
956  
957 if (func)
958 g_async_queue_sort_unlocked (real->queue,
959 real->sort_func,
960 real->sort_user_data);
961  
962 g_async_queue_unlock (real->queue);
963 }
964  
965 /**
966 * g_thread_pool_move_to_front:
967 * @pool: a #GThreadPool
968 * @data: an unprocessed item in the pool
969 *
970 * Moves the item to the front of the queue of unprocessed
971 * items, so that it will be processed next.
972 *
973 * Returns: %TRUE if the item was found and moved
974 *
975 * Since: 2.46
976 */
977 gboolean
978 g_thread_pool_move_to_front (GThreadPool *pool,
979 gpointer data)
980 {
981 GRealThreadPool *real = (GRealThreadPool*) pool;
982 gboolean found;
983  
984 g_async_queue_lock (real->queue);
985  
986 found = g_async_queue_remove_unlocked (real->queue, data);
987 if (found)
988 g_async_queue_push_front_unlocked (real->queue, data);
989  
990 g_async_queue_unlock (real->queue);
991  
992 return found;
993 }
994  
995 /**
996 * g_thread_pool_set_max_idle_time:
997 * @interval: the maximum @interval (in milliseconds)
998 * a thread can be idle
999 *
1000 * This function will set the maximum @interval that a thread
1001 * waiting in the pool for new tasks can be idle for before
1002 * being stopped. This function is similar to calling
1003 * g_thread_pool_stop_unused_threads() on a regular timeout,
1004 * except this is done on a per thread basis.
1005 *
1006 * By setting @interval to 0, idle threads will not be stopped.
1007 *
1008 * The default value is 15000 (15 seconds).
1009 *
1010 * Since: 2.10
1011 */
1012 void
1013 g_thread_pool_set_max_idle_time (guint interval)
1014 {
1015 guint i;
1016  
1017 g_atomic_int_set (&max_idle_time, interval);
1018  
1019 i = g_atomic_int_get (&unused_threads);
1020 if (i > 0)
1021 {
1022 g_atomic_int_inc (&wakeup_thread_serial);
1023 g_async_queue_lock (unused_thread_queue);
1024  
1025 do
1026 {
1027 g_async_queue_push_unlocked (unused_thread_queue,
1028 wakeup_thread_marker);
1029 }
1030 while (--i);
1031  
1032 g_async_queue_unlock (unused_thread_queue);
1033 }
1034 }
1035  
1036 /**
1037 * g_thread_pool_get_max_idle_time:
1038 *
1039 * This function will return the maximum @interval that a
1040 * thread will wait in the thread pool for new tasks before
1041 * being stopped.
1042 *
1043 * If this function returns 0, threads waiting in the thread
1044 * pool for new work are not stopped.
1045 *
1046 * Returns: the maximum @interval (milliseconds) to wait
1047 * for new tasks in the thread pool before stopping the
1048 * thread
1049 *
1050 * Since: 2.10
1051 */
1052 guint
1053 g_thread_pool_get_max_idle_time (void)
1054 {
1055 return g_atomic_int_get (&max_idle_time);
1056 }