1 /* GLIB - Library of useful routines for C programming
2 * Copyright (C) 1995-1997 Peter Mattis, Spencer Kimball and Josh MacDonald
4 * GAsyncQueue: thread pool implementation.
5 * Copyright (C) 2000 Sebastian Wilhelmi; University of Karlsruhe
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.
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.
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.
29 typedef struct _GRealThreadPool GRealThreadPool
;
31 struct _GRealThreadPool
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
;
47 /* Here all unused threads are waiting, depending on their priority */
48 static GAsyncQueue
*unused_thread_queue
[G_THREAD_PRIORITY_URGENT
+ 1][2];
49 static gint unused_threads
= 0;
50 static gint max_unused_threads
= 0;
51 G_LOCK_DEFINE_STATIC (unused_threads
);
53 static GMutex
*inform_mutex
= NULL
;
54 static GCond
*inform_cond
= NULL
;
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
);
61 #define g_thread_should_run(pool, len) \
62 ((pool)->running || (!(pool)->immediate && (len) > 0))
65 g_thread_pool_thread_proxy (gpointer data
)
67 GRealThreadPool
*pool
= data
;
68 gboolean watcher
= FALSE
;
70 g_async_queue_lock (pool
->queue
);
74 gboolean goto_global_pool
=
75 !pool
->pool
.exclusive
&& pool
->pool
.stack_size
== 0;
76 gint len
= g_async_queue_length_unlocked (pool
->queue
);
78 if (g_thread_should_run (pool
, len
))
82 /* This thread is actually not needed here, but it waits
83 * for some time anyway. If during that time a new
84 * request arrives, this saves process
85 * swicthes. Otherwise the thread will go to the global
88 g_get_current_time (&end_time
);
89 end_time
.tv_usec
+= G_USEC_PER_SEC
/ 2; /* Halv a second */
90 if (end_time
.tv_usec
>= G_USEC_PER_SEC
)
92 end_time
.tv_usec
-= G_USEC_PER_SEC
;
96 task
= g_async_queue_timed_pop_unlocked (pool
->queue
, &end_time
);
100 task
= g_async_queue_pop_unlocked (pool
->queue
);
106 if (pool
->num_threads
> pool
->max_threads
&&
107 pool
->max_threads
!= -1)
108 /* We are in fact a superfluous threads, so we go to
109 * the global pool and just hand the data further to
110 * the next one waiting in the queue */
112 g_async_queue_push_unlocked (pool
->queue
, task
);
113 goto_global_pool
= TRUE
;
115 else if (pool
->running
|| !pool
->immediate
)
117 g_async_queue_unlock (pool
->queue
);
118 pool
->pool
.thread_func (task
, pool
->pool
.user_data
);
119 g_async_queue_lock (pool
->queue
);
122 len
= g_async_queue_length_unlocked (pool
->queue
);
125 if (!g_thread_should_run (pool
, len
))
127 g_cond_broadcast (inform_cond
);
128 goto_global_pool
= TRUE
;
132 /* At this pool there are no threads waiting, but tasks are. */
133 goto_global_pool
= FALSE
;
135 else if (len
== 0 && !watcher
&& !pool
->pool
.exclusive
)
137 /* Here neither threads nor tasks are queued and we didn't
138 * just return from a timed wait. We now wait for a limited
139 * time at this pool for new tasks to avoid costly context
141 goto_global_pool
= FALSE
;
146 if (goto_global_pool
)
148 GAsyncQueue
*unused_queue
=
149 unused_thread_queue
[pool
->pool
.priority
][pool
->pool
.bound
? 1 : 0];
152 if (!pool
->running
&& !pool
->waiting
)
154 if (pool
->num_threads
== 0)
156 g_async_queue_unlock (pool
->queue
);
157 g_thread_pool_free_internal (pool
);
159 else if (len
== - pool
->num_threads
)
161 g_thread_pool_wakeup_and_stop_all (pool
);
162 g_async_queue_unlock (pool
->queue
);
166 g_async_queue_unlock (pool
->queue
);
168 g_async_queue_lock (unused_queue
);
170 G_LOCK (unused_threads
);
171 if ((unused_threads
>= max_unused_threads
&&
172 max_unused_threads
!= -1) || pool
->pool
.stack_size
!= 0)
174 G_UNLOCK (unused_threads
);
175 g_async_queue_unlock (unused_queue
);
176 /* Stop this thread */
180 G_UNLOCK (unused_threads
);
182 pool
= g_async_queue_pop_unlocked (unused_queue
);
184 G_LOCK (unused_threads
);
186 G_UNLOCK (unused_threads
);
188 g_async_queue_unlock (unused_queue
);
190 if (pool
== stop_this_thread_marker
)
191 /* Stop this thread */
194 g_async_queue_lock (pool
->queue
);
196 /* pool->num_threads++ is not done here, but in
197 * g_thread_pool_start_thread to make the new started thread
198 * known to the pool, before itself can do it. */
204 g_thread_pool_start_thread (GRealThreadPool
*pool
,
207 gboolean success
= FALSE
;
208 GThreadPriority priority
= pool
->pool
.priority
;
209 guint bound
= pool
->pool
.bound
? 1 : 0;
210 GAsyncQueue
*queue
= unused_thread_queue
[priority
][bound
];
212 if (pool
->num_threads
>= pool
->max_threads
&& pool
->max_threads
!= -1)
213 /* Enough threads are already running */
216 g_async_queue_lock (queue
);
218 if (g_async_queue_length_unlocked (queue
) < 0)
220 /* First we try a thread with the right priority */
221 g_async_queue_push_unlocked (queue
, pool
);
225 g_async_queue_unlock (queue
);
227 /* We will not search for threads with other priorities, because changing
228 * priority is quite unportable */
232 GError
*local_error
= NULL
;
233 /* No thread was found, we have to start a new one */
234 g_thread_create (g_thread_pool_thread_proxy
, pool
,
235 pool
->pool
.stack_size
, FALSE
,
236 bound
, priority
, &local_error
);
240 g_propagate_error (error
, local_error
);
245 /* See comment in g_thread_pool_thread_proxy as to why this is done
246 * here and not there */
252 * @thread_func: a function to execute in the threads of the new thread pool
253 * @max_threads: the maximal number of threads to execute concurrently in
254 * the new thread pool, -1 means no limit
255 * @stack_size: the stack size for the threads of the new thread pool,
256 * 0 means using the standard
257 * @bound: should the threads of the new thread pool be bound?
258 * @priority: a priority for the threads of the new thread pool
259 * @exclusive: should this thread pool be exclusive?
260 * @user_data: user data that is handed over to @thread_func every time it
262 * @error: return location for error
264 * This function creates a new thread pool. All threads created within
265 * this thread pool will have the priority @priority and the stack
266 * size @stack_size and will be bound if and only if @bound is
269 * Whenever you call g_thread_pool_push(), either a new thread is
270 * created or an unused one is reused. At most @max_threads threads
271 * are running concurrently for this thread pool. @max_threads = -1
272 * allows unlimited threads to be created for this thread pool. The
273 * newly created or reused thread now executes the function
274 * @thread_func with the two arguments. The first one is the parameter
275 * to g_thread_pool_push() and the second one is @user_data.
277 * The parameter @exclusive determines, whether the thread pool owns
278 * all threads exclusive or whether the threads are shared
279 * globally. If @exclusive is @TRUE, @max_threads threads are started
280 * immediately and they will run exclusively for this thread pool until
281 * it is destroyed by g_thread_pool_free(). If @exclusive is @FALSE,
282 * threads are created, when needed and shared between all
283 * non-exclusive thread pools. This implies that @max_threads may not
284 * be -1 for exclusive thread pools.
286 * Note, that only threads from a thread pool with a @stack_size of 0
287 * (which means using the standard stack size) will be globally
288 * reused. Threads from a thread pool with a non-zero stack size will
289 * stay only in this thread pool until it is freed and can thus not be
290 * controlled by the g_thread_pool_set_unused_threads() function.
292 * @error can be NULL to ignore errors, or non-NULL to report
293 * errors. An error can only occur, when @exclusive is set to @TRUE and
294 * not all @max_threads threads could be created.
296 * Return value: the new #GThreadPool
299 g_thread_pool_new (GFunc thread_func
,
303 GThreadPriority priority
,
308 GRealThreadPool
*retval
;
309 G_LOCK_DEFINE_STATIC (init
);
311 g_return_val_if_fail (thread_func
, NULL
);
312 g_return_val_if_fail (!exclusive
|| max_threads
!= -1, NULL
);
313 g_return_val_if_fail (max_threads
>= -1, NULL
);
314 g_return_val_if_fail (g_thread_supported (), NULL
);
316 retval
= g_new (GRealThreadPool
, 1);
318 retval
->pool
.thread_func
= thread_func
;
319 retval
->pool
.stack_size
= stack_size
;
320 retval
->pool
.bound
= bound
;
321 retval
->pool
.priority
= priority
;
322 retval
->pool
.exclusive
= exclusive
;
323 retval
->pool
.user_data
= user_data
;
324 retval
->queue
= g_async_queue_new ();
325 retval
->max_threads
= max_threads
;
326 retval
->num_threads
= 0;
327 retval
->running
= TRUE
;
333 inform_mutex
= g_mutex_new ();
334 inform_cond
= g_cond_new ();
335 for (priority
= G_THREAD_PRIORITY_LOW
;
336 priority
< G_THREAD_PRIORITY_URGENT
+ 1; priority
++)
338 unused_thread_queue
[priority
][0] = g_async_queue_new ();
339 unused_thread_queue
[priority
][1] = g_async_queue_new ();
345 if (retval
->pool
.exclusive
)
347 g_async_queue_lock (retval
->queue
);
349 while (retval
->num_threads
< retval
->max_threads
)
351 GError
*local_error
= NULL
;
352 g_thread_pool_start_thread (retval
, &local_error
);
355 g_propagate_error (error
, local_error
);
360 g_async_queue_unlock (retval
->queue
);
363 return (GThreadPool
*) retval
;
367 * g_thread_pool_push:
368 * @pool: a #GThreadPool
369 * @data: a new task for @pool
370 * @error: return location for error
372 * Inserts @data into the list of tasks to be executed by @pool. When
373 * the number of currently running threads is lower than the maximal
374 * allowed number of threads, a new thread is started (or reused) with
375 * the properties given to g_thread_pool_new (). Otherwise @data stays
376 * in the queue until a thread in this pool finishes its previous task
377 * and processes @data.
379 * @error can be NULL to ignore errors, or non-NULL to report
380 * errors. An error can only occur, when a new thread couldn't be
381 * created. In that case @data is simply appended to the queue of work
385 g_thread_pool_push (GThreadPool
*pool
,
389 GRealThreadPool
*real
= (GRealThreadPool
*) pool
;
391 g_return_if_fail (real
);
393 g_async_queue_lock (real
->queue
);
397 g_async_queue_unlock (real
->queue
);
398 g_return_if_fail (real
->running
);
401 if (g_async_queue_length_unlocked (real
->queue
) >= 0)
402 /* No thread is waiting in the queue */
403 g_thread_pool_start_thread (real
, error
);
405 g_async_queue_push_unlocked (real
->queue
, data
);
406 g_async_queue_unlock (real
->queue
);
410 * g_thread_pool_set_max_threads:
411 * @pool: a #GThreadPool
412 * @max_threads: a new maximal number of threads for @pool
413 * @error: return location for error
415 * Sets the maximal allowed number of threads for @pool. A value of -1
416 * means, that the maximal number of threads is unlimited.
418 * Setting @max_threads to 0 means stopping all work for @pool. It is
419 * effectively frozen until @max_threads is set to a non-zero value
422 * A thread is never terminated while calling @thread_func, as
423 * supplied by g_thread_pool_new (). Instead the maximal number of
424 * threads only has effect for the allocation of new threads in
425 * g_thread_pool_push (). A new thread is allocated, whenever the
426 * number of currently running threads in @pool is smaller than the
429 * @error can be NULL to ignore errors, or non-NULL to report
430 * errors. An error can only occur, when a new thread couldn't be
434 g_thread_pool_set_max_threads (GThreadPool
*pool
,
438 GRealThreadPool
*real
= (GRealThreadPool
*) pool
;
441 g_return_if_fail (real
);
442 g_return_if_fail (real
->running
);
443 g_return_if_fail (!real
->pool
.exclusive
|| max_threads
!= -1);
444 g_return_if_fail (max_threads
>= -1);
446 g_async_queue_lock (real
->queue
);
448 real
->max_threads
= max_threads
;
451 to_start
= real
->max_threads
- real
->num_threads
;
453 to_start
= g_async_queue_length_unlocked (real
->queue
);
455 for ( ; to_start
> 0; to_start
--)
457 GError
*local_error
= NULL
;
458 g_thread_pool_start_thread (real
, &local_error
);
461 g_propagate_error (error
, local_error
);
466 g_async_queue_unlock (real
->queue
);
470 * g_thread_pool_get_max_threads:
471 * @pool: a #GThreadPool
473 * Returns the maximal number of threads for @pool.
475 * Return value: the maximal number of threads
478 g_thread_pool_get_max_threads (GThreadPool
*pool
)
480 GRealThreadPool
*real
= (GRealThreadPool
*) pool
;
483 g_return_val_if_fail (real
, 0);
484 g_return_val_if_fail (real
->running
, 0);
486 g_async_queue_lock (real
->queue
);
488 retval
= real
->max_threads
;
490 g_async_queue_unlock (real
->queue
);
496 * g_thread_pool_get_num_threads:
497 * @pool: a #GThreadPool
499 * Returns the number of threads currently running in @pool.
501 * Return value: the number of threads currently running
504 g_thread_pool_get_num_threads (GThreadPool
*pool
)
506 GRealThreadPool
*real
= (GRealThreadPool
*) pool
;
509 g_return_val_if_fail (real
, 0);
510 g_return_val_if_fail (real
->running
, 0);
512 g_async_queue_lock (real
->queue
);
514 retval
= real
->num_threads
;
516 g_async_queue_unlock (real
->queue
);
522 * g_thread_pool_unprocessed:
523 * @pool: a #GThreadPool
525 * Returns the number of tasks still unprocessed in @pool.
527 * Return value: the number of unprocessed tasks
530 g_thread_pool_unprocessed (GThreadPool
*pool
)
532 GRealThreadPool
*real
= (GRealThreadPool
*) pool
;
535 g_return_val_if_fail (real
, 0);
536 g_return_val_if_fail (real
->running
, 0);
538 unprocessed
= g_async_queue_length (real
->queue
);
540 return MAX (unprocessed
, 0);
544 * g_thread_pool_free:
545 * @pool: a #GThreadPool
546 * @immediate: should @pool shut down immediately?
547 * @wait: should the function wait for all tasks to be finished?
549 * Frees all resources allocated for @pool.
551 * If @immediate is #TRUE, no new task is processed for
552 * @pool. Otherwise @pool is not freed before the last task is
553 * processed. Note however, that no thread of this pool is
554 * interrupted, while processing a task. Instead at least all still
555 * running threads can finish their tasks before the @pool is freed.
557 * If @wait is #TRUE, the functions does not return before all tasks
558 * to be processed (dependent on @immediate, whether all or only the
559 * currently running) are ready. Otherwise the function returns immediately.
561 * After calling this function @pool must not be used anymore.
564 g_thread_pool_free (GThreadPool
*pool
,
568 GRealThreadPool
*real
= (GRealThreadPool
*) pool
;
570 g_return_if_fail (real
);
571 g_return_if_fail (real
->running
);
572 /* It there's no thread allowed here, there is not much sense in
573 * not stopping this pool immediately, when it's not empty */
574 g_return_if_fail (immediate
|| real
->max_threads
!= 0 ||
575 g_async_queue_length (real
->queue
) == 0);
577 g_async_queue_lock (real
->queue
);
579 real
->running
= FALSE
;
580 real
->immediate
= immediate
;
581 real
->waiting
= wait
;
585 g_mutex_lock (inform_mutex
);
586 while (g_async_queue_length_unlocked (real
->queue
) != -real
->num_threads
)
588 g_async_queue_unlock (real
->queue
);
589 g_cond_wait (inform_cond
, inform_mutex
);
590 g_async_queue_lock (real
->queue
);
592 g_mutex_unlock (inform_mutex
);
595 if (g_async_queue_length_unlocked (real
->queue
) == -real
->num_threads
)
597 /* No thread is currently doing something (and nothing is left
598 * to process in the queue) */
599 if (real
->num_threads
== 0) /* No threads left, we clean up */
601 g_async_queue_unlock (real
->queue
);
602 g_thread_pool_free_internal (real
);
606 g_thread_pool_wakeup_and_stop_all (real
);
609 real
->waiting
= FALSE
; /* The last thread should cleanup the pool */
610 g_async_queue_unlock (real
->queue
);
614 g_thread_pool_free_internal (GRealThreadPool
* pool
)
616 g_return_if_fail (pool
);
617 g_return_if_fail (!pool
->running
);
618 g_return_if_fail (pool
->num_threads
== 0);
620 g_async_queue_unref (pool
->queue
);
626 g_thread_pool_wakeup_and_stop_all (GRealThreadPool
* pool
)
630 g_return_if_fail (pool
);
631 g_return_if_fail (!pool
->running
);
632 g_return_if_fail (pool
->num_threads
!= 0);
633 g_return_if_fail (g_async_queue_length_unlocked (pool
->queue
) ==
636 pool
->immediate
= TRUE
;
637 for (i
= 0; i
< pool
->num_threads
; i
++)
638 g_async_queue_push_unlocked (pool
->queue
, GUINT_TO_POINTER (1));
642 * g_thread_pool_set_max_unused_threads:
643 * @max_threads: maximal number of unused threads
645 * Sets the maximal number of unused threads to @max_threads. If
646 * @max_threads is -1, no limit is imposed on the number of unused
650 g_thread_pool_set_max_unused_threads (gint max_threads
)
652 g_return_if_fail (max_threads
>= -1);
654 G_LOCK (unused_threads
);
656 max_unused_threads
= max_threads
;
658 if (max_unused_threads
< unused_threads
&& max_unused_threads
!= -1)
660 guint close_down_num
= unused_threads
- max_unused_threads
;
662 while (close_down_num
> 0)
664 GThreadPriority priority
;
667 guint old_close_down_num
= close_down_num
;
668 for (priority
= G_THREAD_PRIORITY_LOW
;
669 priority
< G_THREAD_PRIORITY_URGENT
+ 1 && close_down_num
> 0;
672 for (bound
= 0; bound
< 2; bound
++)
674 GAsyncQueue
*queue
= unused_thread_queue
[priority
][bound
];
675 g_async_queue_lock (queue
);
677 if (g_async_queue_length_unlocked (queue
) < 0)
679 g_async_queue_push_unlocked (queue
,
680 stop_this_thread_marker
);
684 g_async_queue_unlock (queue
);
688 /* Just to make sure, there are no counting problems */
689 g_assert (old_close_down_num
!= close_down_num
);
693 G_UNLOCK (unused_threads
);
697 * g_thread_pool_get_max_unused_threads:
699 * Returns the maximal allowed number of unused threads.
701 * Return value: the maximal number of unused threads
704 g_thread_pool_get_max_unused_threads (void)
708 G_LOCK (unused_threads
);
709 retval
= max_unused_threads
;
710 G_UNLOCK (unused_threads
);
716 * g_thread_pool_get_num_unused_threads:
718 * Returns the number of currently unused threads.
720 * Return value: the number of currently unused threads
722 guint
g_thread_pool_get_num_unused_threads (void)
726 G_LOCK (unused_threads
);
727 retval
= unused_threads
;
728 G_UNLOCK (unused_threads
);
734 * g_thread_pool_stop_unused_threads:
736 * Stops all currently unused threads. This does not change the
737 * maximal number of unused threads. This function can be used to
738 * regularly stop all unused threads e.g. from g_timeout_add().
740 void g_thread_pool_stop_unused_threads (void)
742 guint oldval
= g_thread_pool_get_max_unused_threads ();
743 g_thread_pool_set_max_unused_threads (0);
744 g_thread_pool_set_max_unused_threads (oldval
);