2 * Copyright (C) 1999,2000 Erik Walthinsen <omega@cse.ogi.edu>
3 * 2005 Wim Taymans <wim@fluendo.com>
5 * gsttask.c: Streaming tasks
7 * This library is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU Library 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 * Library General Public License for more details.
17 * You should have received a copy of the GNU Library 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.
25 * @short_description: Abstraction of GStreamer streaming threads.
26 * @see_also: #GstElement, #GstPad
28 * #GstTask is used by #GstElement and #GstPad to provide the data passing
29 * threads in a #GstPipeline.
31 * A #GstPad will typically start a #GstTask to push or pull data to/from the
32 * peer pads. Most source elements start a #GstTask to push data. In some cases
33 * a demuxer element can start a #GstTask to pull data from a peer element. This
34 * is typically done when the demuxer can perform random access on the upstream
35 * peer element for improved performance.
37 * Although convenience functions exist on #GstPad to start/pause/stop tasks, it
38 * might sometimes be needed to create a #GstTask manually if it is not related to
41 * Before the #GstTask can be run, it needs a #GStaticRecMutex that can be set with
42 * gst_task_set_lock().
44 * The task can be started, paused and stopped with gst_task_start(), gst_task_pause()
45 * and gst_task_stop() respectively or with the gst_task_set_state() function.
47 * A #GstTask will repeatedly call the #GstTaskFunction with the user data
48 * that was provided when creating the task with gst_task_new(). While calling
49 * the function it will acquire the provided lock. The provided lock is released
50 * when the task pauses or stops.
52 * Stopping a task with gst_task_stop() will not immediately make sure the task is
53 * not running anymore. Use gst_task_join() to make sure the task is completely
54 * stopped and the thread is stopped.
56 * After creating a #GstTask, use gst_object_unref() to free its resources. This can
57 * only be done it the task is not running anymore.
59 * Task functions can send a #GstMessage to send out-of-band data to the
60 * application. The application can receive messages from the #GstBus in its
63 * For debugging perposes, the task will configure its object name as the thread
64 * name on Linux. Please note that the object name should be configured before the
65 * task is started; changing the object name after the task has been started, has
66 * no effect on the thread name.
68 * Last reviewed on 2010-03-15 (0.10.29)
71 /* FIXME 0.11: suppress warnings for deprecated API such as GStaticRecMutex
72 * with newer GLib versions (>= 2.31.0) */
73 #define GLIB_DISABLE_DEPRECATION_WARNINGS
74 #include "gst_private.h"
78 #include "glib-compat-private.h"
82 #ifdef HAVE_SYS_PRCTL_H
83 #include <sys/prctl.h>
86 GST_DEBUG_CATEGORY_STATIC (task_debug);
87 #define GST_CAT_DEFAULT (task_debug)
89 #define SET_TASK_STATE(t,s) (g_atomic_int_set (&GST_TASK_STATE(t), (s)))
90 #define GET_TASK_STATE(t) ((GstTaskState) g_atomic_int_get (&GST_TASK_STATE(t)))
92 #define GST_TASK_GET_PRIVATE(obj) \
93 (G_TYPE_INSTANCE_GET_PRIVATE ((obj), GST_TYPE_TASK, GstTaskPrivate))
95 struct _GstTaskPrivate
97 /* callbacks for managing the thread of this task */
98 GstTaskThreadCallbacks thr_callbacks;
99 gpointer thr_user_data;
100 GDestroyNotify thr_notify;
103 GThreadPriority priority;
105 /* configured pool */
108 /* remember the pool and id that is currently running. */
110 GstTaskPool *pool_id;
116 struct _THREADNAME_INFO
118 DWORD dwType; // must be 0x1000
119 LPCSTR szName; // pointer to name (in user addr space)
120 DWORD dwThreadID; // thread ID (-1=caller thread)
121 DWORD dwFlags; // reserved for future use, must be zero
123 typedef struct _THREADNAME_INFO THREADNAME_INFO;
126 SetThreadName (DWORD dwThreadID, LPCSTR szThreadName)
128 THREADNAME_INFO info;
129 info.dwType = 0x1000;
130 info.szName = szThreadName;
131 info.dwThreadID = dwThreadID;
135 RaiseException (0x406D1388, 0, sizeof (info) / sizeof (DWORD),
138 __except (EXCEPTION_CONTINUE_EXECUTION) {
143 static void gst_task_finalize (GObject * object);
145 static void gst_task_func (GstTask * task);
147 static GStaticMutex pool_lock = G_STATIC_MUTEX_INIT;
151 GST_DEBUG_CATEGORY_INIT (task_debug, "task", 0, "Processing tasks"); \
154 G_DEFINE_TYPE_WITH_CODE (GstTask, gst_task, GST_TYPE_OBJECT, _do_init);
157 init_klass_pool (GstTaskClass * klass)
159 g_static_mutex_lock (&pool_lock);
161 gst_task_pool_cleanup (klass->pool);
162 gst_object_unref (klass->pool);
164 klass->pool = gst_task_pool_new ();
165 gst_task_pool_prepare (klass->pool, NULL);
166 g_static_mutex_unlock (&pool_lock);
170 gst_task_class_init (GstTaskClass * klass)
172 GObjectClass *gobject_class;
174 gobject_class = (GObjectClass *) klass;
176 g_type_class_add_private (klass, sizeof (GstTaskPrivate));
178 gobject_class->finalize = gst_task_finalize;
180 init_klass_pool (klass);
184 gst_task_init (GstTask * task)
188 klass = GST_TASK_GET_CLASS (task);
190 task->priv = GST_TASK_GET_PRIVATE (task);
191 task->running = FALSE;
194 task->cond = g_cond_new ();
195 SET_TASK_STATE (task, GST_TASK_STOPPED);
196 task->priv->prio_set = FALSE;
198 /* use the default klass pool for this task, users can
199 * override this later */
200 g_static_mutex_lock (&pool_lock);
201 task->priv->pool = gst_object_ref (klass->pool);
202 g_static_mutex_unlock (&pool_lock);
206 gst_task_finalize (GObject * object)
208 GstTask *task = GST_TASK (object);
209 GstTaskPrivate *priv = task->priv;
211 GST_DEBUG ("task %p finalize", task);
213 if (priv->thr_notify)
214 priv->thr_notify (priv->thr_user_data);
215 priv->thr_notify = NULL;
216 priv->thr_user_data = NULL;
218 gst_object_unref (priv->pool);
220 /* task thread cannot be running here since it holds a ref
221 * to the task so that the finalize could not have happened */
222 g_cond_free (task->cond);
225 G_OBJECT_CLASS (gst_task_parent_class)->finalize (object);
228 /* should be called with the object LOCK */
230 gst_task_configure_name (GstTask * task)
232 #if defined(HAVE_SYS_PRCTL_H) && defined(PR_SET_NAME)
234 gchar thread_name[17] = { 0, };
236 GST_OBJECT_LOCK (task);
237 name = GST_OBJECT_NAME (task);
239 /* set the thread name to something easily identifiable */
240 if (!snprintf (thread_name, 17, "%s", GST_STR_NULL (name))) {
241 GST_DEBUG_OBJECT (task, "Could not create thread name for '%s'", name);
243 GST_DEBUG_OBJECT (task, "Setting thread name to '%s'", thread_name);
244 if (prctl (PR_SET_NAME, (unsigned long int) thread_name, 0, 0, 0))
245 GST_DEBUG_OBJECT (task, "Failed to set thread name");
247 GST_OBJECT_UNLOCK (task);
251 name = GST_OBJECT_NAME (task);
253 /* set the thread name to something easily identifiable */
254 GST_DEBUG_OBJECT (task, "Setting thread name to '%s'", name);
255 SetThreadName (-1, name);
260 gst_task_func (GstTask * task)
262 GStaticRecMutex *lock;
264 GstTaskPrivate *priv;
268 tself = g_thread_self ();
270 GST_DEBUG ("Entering task %p, thread %p", task, tself);
272 /* we have to grab the lock to get the mutex. We also
273 * mark our state running so that nobody can mess with
275 GST_OBJECT_LOCK (task);
276 if (GET_TASK_STATE (task) == GST_TASK_STOPPED)
278 lock = GST_TASK_GET_LOCK (task);
279 if (G_UNLIKELY (lock == NULL))
281 task->thread = tself;
282 /* only update the priority when it was changed */
283 if (priv->prio_set) {
284 #if !GLIB_CHECK_VERSION (2, 31, 0)
285 g_thread_set_priority (tself, priv->priority);
287 GST_INFO_OBJECT (task, "Thread priorities no longer have any effect");
290 GST_OBJECT_UNLOCK (task);
292 /* fire the enter_thread callback when we need to */
293 if (priv->thr_callbacks.enter_thread)
294 priv->thr_callbacks.enter_thread (task, tself, priv->thr_user_data);
296 /* locking order is TASK_LOCK, LOCK */
297 g_static_rec_mutex_lock (lock);
298 /* configure the thread name now */
299 gst_task_configure_name (task);
301 while (G_LIKELY (GET_TASK_STATE (task) != GST_TASK_STOPPED)) {
302 if (G_UNLIKELY (GET_TASK_STATE (task) == GST_TASK_PAUSED)) {
303 GST_OBJECT_LOCK (task);
304 while (G_UNLIKELY (GST_TASK_STATE (task) == GST_TASK_PAUSED)) {
305 g_static_rec_mutex_unlock (lock);
307 GST_TASK_SIGNAL (task);
308 GST_TASK_WAIT (task);
309 GST_OBJECT_UNLOCK (task);
310 /* locking order.. */
311 g_static_rec_mutex_lock (lock);
313 GST_OBJECT_LOCK (task);
314 if (G_UNLIKELY (GET_TASK_STATE (task) == GST_TASK_STOPPED)) {
315 GST_OBJECT_UNLOCK (task);
319 GST_OBJECT_UNLOCK (task);
322 task->func (task->data);
325 g_static_rec_mutex_unlock (lock);
327 GST_OBJECT_LOCK (task);
331 if (priv->thr_callbacks.leave_thread) {
332 /* fire the leave_thread callback when we need to. We need to do this before
333 * we signal the task and with the task lock released. */
334 GST_OBJECT_UNLOCK (task);
335 priv->thr_callbacks.leave_thread (task, tself, priv->thr_user_data);
336 GST_OBJECT_LOCK (task);
338 /* restore normal priority when releasing back into the pool, we will not
339 * touch the priority when a custom callback has been installed. */
340 #if !GLIB_CHECK_VERSION (2, 31, 0)
341 g_thread_set_priority (tself, G_THREAD_PRIORITY_NORMAL);
344 /* now we allow messing with the lock again by setting the running flag to
345 * FALSE. Together with the SIGNAL this is the sign for the _join() to
347 * Note that we still have not dropped the final ref on the task. We could
348 * check here if there is a pending join() going on and drop the last ref
349 * before releasing the lock as we can be sure that a ref is held by the
350 * caller of the join(). */
351 task->running = FALSE;
352 GST_TASK_SIGNAL (task);
353 GST_OBJECT_UNLOCK (task);
355 GST_DEBUG ("Exit task %p, thread %p", task, g_thread_self ());
357 gst_object_unref (task);
362 g_warning ("starting task without a lock");
368 * gst_task_cleanup_all:
370 * Wait for all tasks to be stopped. This is mainly used internally
371 * to ensure proper cleanup of internal data structures in test suites.
376 gst_task_cleanup_all (void)
380 if ((klass = g_type_class_peek (GST_TYPE_TASK))) {
381 init_klass_pool (klass);
387 * @func: The #GstTaskFunction to use
388 * @data: (closure): User data to pass to @func
390 * Create a new Task that will repeatedly call the provided @func
391 * with @data as a parameter. Typically the task will run in
394 * The function cannot be changed after the task has been created. You
395 * must create a new #GstTask to change the function.
397 * This function will not yet create and start a thread. Use gst_task_start() or
398 * gst_task_pause() to create and start the GThread.
400 * Before the task can be used, a #GStaticRecMutex must be configured using the
401 * gst_task_set_lock() function. This lock will always be acquired while
404 * Returns: (transfer full): A new #GstTask.
409 gst_task_new (GstTaskFunction func, gpointer data)
413 task = g_object_newv (GST_TYPE_TASK, 0, NULL);
417 GST_DEBUG ("Created task %p", task);
424 * @task: The #GstTask to use
425 * @mutex: The #GMutex to use
427 * Set the mutex used by the task. The mutex will be acquired before
428 * calling the #GstTaskFunction.
430 * This function has to be called before calling gst_task_pause() or
436 gst_task_set_lock (GstTask * task, GStaticRecMutex * mutex)
438 GST_OBJECT_LOCK (task);
439 if (G_UNLIKELY (task->running))
441 GST_TASK_GET_LOCK (task) = mutex;
442 GST_OBJECT_UNLOCK (task);
449 GST_OBJECT_UNLOCK (task);
450 g_warning ("cannot call set_lock on a running task");
455 * gst_task_set_priority:
457 * @priority: a new priority for @task
459 * Changes the priority of @task to @priority.
461 * Note: try not to depend on task priorities.
468 gst_task_set_priority (GstTask * task, GThreadPriority priority)
470 GstTaskPrivate *priv;
473 g_return_if_fail (GST_IS_TASK (task));
477 GST_OBJECT_LOCK (task);
478 priv->prio_set = TRUE;
479 priv->priority = priority;
480 thread = task->thread;
481 if (thread != NULL) {
482 /* if this task already has a thread, we can configure the priority right
483 * away, else we do that when we assign a thread to the task. */
484 #if !GLIB_CHECK_VERSION (2, 31, 0)
485 g_thread_set_priority (thread, priority);
487 GST_INFO_OBJECT (task, "Thread priorities no longer have any effect");
490 GST_OBJECT_UNLOCK (task);
497 * Get the #GstTaskPool that this task will use for its streaming
502 * Returns: (transfer full): the #GstTaskPool used by @task. gst_object_unref()
508 gst_task_get_pool (GstTask * task)
511 GstTaskPrivate *priv;
513 g_return_val_if_fail (GST_IS_TASK (task), NULL);
517 GST_OBJECT_LOCK (task);
518 result = gst_object_ref (priv->pool);
519 GST_OBJECT_UNLOCK (task);
527 * @pool: (transfer none): a #GstTaskPool
529 * Set @pool as the new GstTaskPool for @task. Any new streaming threads that
530 * will be created by @task will now use @pool.
537 gst_task_set_pool (GstTask * task, GstTaskPool * pool)
540 GstTaskPrivate *priv;
542 g_return_if_fail (GST_IS_TASK (task));
543 g_return_if_fail (GST_IS_TASK_POOL (pool));
547 GST_OBJECT_LOCK (task);
548 if (priv->pool != pool) {
550 priv->pool = gst_object_ref (pool);
553 GST_OBJECT_UNLOCK (task);
556 gst_object_unref (old);
561 * gst_task_set_thread_callbacks:
562 * @task: The #GstTask to use
563 * @callbacks: (in): a #GstTaskThreadCallbacks pointer
564 * @user_data: (closure): user data passed to the callbacks
565 * @notify: called when @user_data is no longer referenced
567 * Set callbacks which will be executed when a new thread is needed, the thread
568 * function is entered and left and when the thread is joined.
570 * By default a thread for @task will be created from a default thread pool.
572 * Objects can use custom GThreads or can perform additional configuration of
573 * the threads (such as changing the thread priority) by installing callbacks.
580 gst_task_set_thread_callbacks (GstTask * task,
581 GstTaskThreadCallbacks * callbacks, gpointer user_data,
582 GDestroyNotify notify)
584 GDestroyNotify old_notify;
586 g_return_if_fail (task != NULL);
587 g_return_if_fail (GST_IS_TASK (task));
588 g_return_if_fail (callbacks != NULL);
590 GST_OBJECT_LOCK (task);
591 old_notify = task->priv->thr_notify;
596 old_data = task->priv->thr_user_data;
598 task->priv->thr_user_data = NULL;
599 task->priv->thr_notify = NULL;
600 GST_OBJECT_UNLOCK (task);
602 old_notify (old_data);
604 GST_OBJECT_LOCK (task);
606 task->priv->thr_callbacks = *callbacks;
607 task->priv->thr_user_data = user_data;
608 task->priv->thr_notify = notify;
609 GST_OBJECT_UNLOCK (task);
613 * gst_task_get_state:
614 * @task: The #GstTask to query
616 * Get the current state of the task.
618 * Returns: The #GstTaskState of the task
623 gst_task_get_state (GstTask * task)
627 g_return_val_if_fail (GST_IS_TASK (task), GST_TASK_STOPPED);
629 result = GET_TASK_STATE (task);
634 /* make sure the task is running and start a thread if it's not.
635 * This function must be called with the task LOCK. */
637 start_task (GstTask * task)
640 GError *error = NULL;
641 GstTaskPrivate *priv;
645 /* new task, We ref before so that it remains alive while
646 * the thread is running. */
647 gst_object_ref (task);
648 /* mark task as running so that a join will wait until we schedule
649 * and exit the task function. */
650 task->running = TRUE;
652 /* push on the thread pool, we remember the original pool because the user
653 * could change it later on and then we join to the wrong pool. */
654 priv->pool_id = gst_object_ref (priv->pool);
656 gst_task_pool_push (priv->pool_id, (GstTaskPoolFunction) gst_task_func,
660 g_warning ("failed to create thread: %s", error->message);
661 g_error_free (error);
669 * gst_task_set_state:
671 * @state: the new task state
673 * Sets the state of @task to @state.
675 * The @task must have a lock associated with it using
676 * gst_task_set_lock() when going to GST_TASK_STARTED or GST_TASK_PAUSED or
677 * this function will return %FALSE.
681 * Returns: %TRUE if the state could be changed.
686 gst_task_set_state (GstTask * task, GstTaskState state)
691 g_return_val_if_fail (GST_IS_TASK (task), FALSE);
693 GST_DEBUG_OBJECT (task, "Changing task %p to state %d", task, state);
695 GST_OBJECT_LOCK (task);
696 if (state != GST_TASK_STOPPED)
697 if (G_UNLIKELY (GST_TASK_GET_LOCK (task) == NULL))
700 /* if the state changed, do our thing */
701 old = GET_TASK_STATE (task);
703 SET_TASK_STATE (task, state);
705 case GST_TASK_STOPPED:
706 /* If the task already has a thread scheduled we don't have to do
708 if (G_UNLIKELY (!task->running))
709 res = start_task (task);
711 case GST_TASK_PAUSED:
712 /* when we are paused, signal to go to the new state */
713 GST_TASK_SIGNAL (task);
715 case GST_TASK_STARTED:
716 /* if we were started, we'll go to the new state after the next
721 GST_OBJECT_UNLOCK (task);
728 GST_WARNING_OBJECT (task, "state %d set on task without a lock", state);
729 GST_OBJECT_UNLOCK (task);
730 g_warning ("task without a lock can't be set to state %d", state);
737 * @task: The #GstTask to start
739 * Starts @task. The @task must have a lock associated with it using
740 * gst_task_set_lock() or this function will return %FALSE.
742 * Returns: %TRUE if the task could be started.
747 gst_task_start (GstTask * task)
749 return gst_task_set_state (task, GST_TASK_STARTED);
754 * @task: The #GstTask to stop
756 * Stops @task. This method merely schedules the task to stop and
757 * will not wait for the task to have completely stopped. Use
758 * gst_task_join() to stop and wait for completion.
760 * Returns: %TRUE if the task could be stopped.
765 gst_task_stop (GstTask * task)
767 return gst_task_set_state (task, GST_TASK_STOPPED);
772 * @task: The #GstTask to pause
774 * Pauses @task. This method can also be called on a task in the
775 * stopped state, in which case a thread will be started and will remain
776 * in the paused state. This function does not wait for the task to complete
779 * Returns: %TRUE if the task could be paused.
784 gst_task_pause (GstTask * task)
786 return gst_task_set_state (task, GST_TASK_PAUSED);
791 * @task: The #GstTask to join
793 * Joins @task. After this call, it is safe to unref the task
794 * and clean up the lock set with gst_task_set_lock().
796 * The task will automatically be stopped with this call.
798 * This function cannot be called from within a task function as this
799 * would cause a deadlock. The function will detect this and print a
802 * Returns: %TRUE if the task could be joined.
807 gst_task_join (GstTask * task)
810 GstTaskPrivate *priv;
812 GstTaskPool *pool = NULL;
816 g_return_val_if_fail (GST_IS_TASK (task), FALSE);
818 tself = g_thread_self ();
820 GST_DEBUG_OBJECT (task, "Joining task %p, thread %p", task, tself);
822 /* we don't use a real thread join here because we are using
824 GST_OBJECT_LOCK (task);
825 if (G_UNLIKELY (tself == task->thread))
827 SET_TASK_STATE (task, GST_TASK_STOPPED);
828 /* signal the state change for when it was blocked in PAUSED. */
829 GST_TASK_SIGNAL (task);
830 /* we set the running flag when pushing the task on the thread pool.
831 * This means that the task function might not be called when we try
832 * to join it here. */
833 while (G_LIKELY (task->running))
834 GST_TASK_WAIT (task);
835 /* clean the thread */
837 /* get the id and pool to join */
838 pool = priv->pool_id;
840 priv->pool_id = NULL;
842 GST_OBJECT_UNLOCK (task);
846 gst_task_pool_join (pool, id);
847 gst_object_unref (pool);
850 GST_DEBUG_OBJECT (task, "Joined task %p", task);
857 GST_WARNING_OBJECT (task, "trying to join task from its thread");
858 GST_OBJECT_UNLOCK (task);
859 g_warning ("\nTrying to join task %p from its thread would deadlock.\n"
860 "You cannot change the state of an element from its streaming\n"
861 "thread. Use g_idle_add() or post a GstMessage on the bus to\n"
862 "schedule the state change from the main thread.\n", task);