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_create(). 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 * Last reviewed on 2006-02-13 (0.10.4)
66 #include "gst_private.h"
71 GST_DEBUG_CATEGORY_STATIC (task_debug);
72 #define GST_CAT_DEFAULT (task_debug)
74 #define GST_TASK_GET_PRIVATE(obj) \
75 (G_TYPE_INSTANCE_GET_PRIVATE ((obj), GST_TYPE_TASK, GstTaskPrivate))
77 struct _GstTaskPrivate
79 /* callbacks for managing the thread of this task */
80 GstTaskThreadCallbacks thr_callbacks;
81 gpointer thr_user_data;
82 GDestroyNotify thr_notify;
85 GThreadPriority priority;
90 /* remember the pool and id that is currently running. */
95 static void gst_task_finalize (GObject * object);
97 static void gst_task_func (GstTask * task);
99 static GStaticMutex pool_lock = G_STATIC_MUTEX_INIT;
103 GST_DEBUG_CATEGORY_INIT (task_debug, "task", 0, "Processing tasks"); \
106 G_DEFINE_TYPE_WITH_CODE (GstTask, gst_task, GST_TYPE_OBJECT, _do_init);
109 init_klass_pool (GstTaskClass * klass)
111 g_static_mutex_lock (&pool_lock);
113 gst_task_pool_cleanup (klass->pool);
114 gst_object_unref (klass->pool);
116 klass->pool = gst_task_pool_new ();
117 gst_task_pool_prepare (klass->pool, NULL);
118 g_static_mutex_unlock (&pool_lock);
122 gst_task_class_init (GstTaskClass * klass)
124 GObjectClass *gobject_class;
126 gobject_class = (GObjectClass *) klass;
128 g_type_class_add_private (klass, sizeof (GstTaskPrivate));
130 gobject_class->finalize = gst_task_finalize;
132 init_klass_pool (klass);
136 gst_task_init (GstTask * task)
140 klass = GST_TASK_GET_CLASS (task);
142 task->priv = GST_TASK_GET_PRIVATE (task);
143 task->running = FALSE;
144 task->abidata.ABI.thread = NULL;
146 task->cond = g_cond_new ();
147 task->state = GST_TASK_STOPPED;
148 task->priv->prio_set = FALSE;
150 /* use the default klass pool for this task, users can
151 * override this later */
152 g_static_mutex_lock (&pool_lock);
153 task->priv->pool = gst_object_ref (klass->pool);
154 g_static_mutex_unlock (&pool_lock);
158 gst_task_finalize (GObject * object)
160 GstTask *task = GST_TASK (object);
161 GstTaskPrivate *priv = task->priv;
163 GST_DEBUG ("task %p finalize", task);
165 if (priv->thr_notify)
166 priv->thr_notify (priv->thr_user_data);
167 priv->thr_notify = NULL;
168 priv->thr_user_data = NULL;
170 gst_object_unref (priv->pool);
172 /* task thread cannot be running here since it holds a ref
173 * to the task so that the finalize could not have happened */
174 g_cond_free (task->cond);
177 G_OBJECT_CLASS (gst_task_parent_class)->finalize (object);
181 gst_task_func (GstTask * task)
183 GStaticRecMutex *lock;
185 GstTaskPrivate *priv;
189 tself = g_thread_self ();
191 GST_DEBUG ("Entering task %p, thread %p", task, tself);
193 /* we have to grab the lock to get the mutex. We also
194 * mark our state running so that nobody can mess with
196 GST_OBJECT_LOCK (task);
197 if (task->state == GST_TASK_STOPPED)
199 lock = GST_TASK_GET_LOCK (task);
200 if (G_UNLIKELY (lock == NULL))
202 task->abidata.ABI.thread = tself;
203 /* only update the priority when it was changed */
205 g_thread_set_priority (tself, priv->priority);
206 GST_OBJECT_UNLOCK (task);
208 /* fire the enter_thread callback when we need to */
209 if (priv->thr_callbacks.enter_thread)
210 priv->thr_callbacks.enter_thread (task, tself, priv->thr_user_data);
212 /* locking order is TASK_LOCK, LOCK */
213 g_static_rec_mutex_lock (lock);
214 GST_OBJECT_LOCK (task);
215 while (G_LIKELY (task->state != GST_TASK_STOPPED)) {
216 while (G_UNLIKELY (task->state == GST_TASK_PAUSED)) {
219 t = g_static_rec_mutex_unlock_full (lock);
221 g_warning ("wrong STREAM_LOCK count %d", t);
223 GST_TASK_SIGNAL (task);
224 GST_TASK_WAIT (task);
225 GST_OBJECT_UNLOCK (task);
226 /* locking order.. */
228 g_static_rec_mutex_lock_full (lock, t);
230 GST_OBJECT_LOCK (task);
231 if (G_UNLIKELY (task->state == GST_TASK_STOPPED))
234 GST_OBJECT_UNLOCK (task);
236 task->func (task->data);
238 GST_OBJECT_LOCK (task);
241 GST_OBJECT_UNLOCK (task);
242 g_static_rec_mutex_unlock (lock);
244 GST_OBJECT_LOCK (task);
245 task->abidata.ABI.thread = NULL;
248 if (priv->thr_callbacks.leave_thread) {
249 /* fire the leave_thread callback when we need to. We need to do this before
250 * we signal the task and with the task lock released. */
251 GST_OBJECT_UNLOCK (task);
252 priv->thr_callbacks.leave_thread (task, tself, priv->thr_user_data);
253 GST_OBJECT_LOCK (task);
255 /* restore normal priority when releasing back into the pool, we will not
256 * touch the priority when a custom callback has been installed. */
257 g_thread_set_priority (tself, G_THREAD_PRIORITY_NORMAL);
259 /* now we allow messing with the lock again by setting the running flag to
260 * FALSE. Together with the SIGNAL this is the sign for the _join() to
262 * Note that we still have not dropped the final ref on the task. We could
263 * check here if there is a pending join() going on and drop the last ref
264 * before releasing the lock as we can be sure that a ref is held by the
265 * caller of the join(). */
266 task->running = FALSE;
267 GST_TASK_SIGNAL (task);
268 GST_OBJECT_UNLOCK (task);
270 GST_DEBUG ("Exit task %p, thread %p", task, g_thread_self ());
272 gst_object_unref (task);
277 g_warning ("starting task without a lock");
283 * gst_task_cleanup_all:
285 * Wait for all tasks to be stopped. This is mainly used internally
286 * to ensure proper cleanup of internal data structures in test suites.
291 gst_task_cleanup_all (void)
295 if ((klass = g_type_class_peek (GST_TYPE_TASK))) {
296 init_klass_pool (klass);
302 * @func: The #GstTaskFunction to use
303 * @data: User data to pass to @func
305 * Create a new Task that will repeatedly call the provided @func
306 * with @data as a parameter. Typically the task will run in
309 * The function cannot be changed after the task has been created. You
310 * must create a new #GstTask to change the function.
312 * This function will not yet create and start a thread. Use gst_task_start() or
313 * gst_task_pause() to create and start the GThread.
315 * Before the task can be used, a #GStaticRecMutex must be configured using the
316 * gst_task_set_lock() function. This lock will always be acquired while
319 * Returns: A new #GstTask.
324 gst_task_create (GstTaskFunction func, gpointer data)
328 task = g_object_newv (GST_TYPE_TASK, 0, NULL);
332 GST_DEBUG ("Created task %p", task);
339 * @task: The #GstTask to use
340 * @mutex: The #GMutex to use
342 * Set the mutex used by the task. The mutex will be acquired before
343 * calling the #GstTaskFunction.
345 * This function has to be called before calling gst_task_pause() or
351 gst_task_set_lock (GstTask * task, GStaticRecMutex * mutex)
353 GST_OBJECT_LOCK (task);
354 if (G_UNLIKELY (task->running))
356 GST_TASK_GET_LOCK (task) = mutex;
357 GST_OBJECT_UNLOCK (task);
364 GST_OBJECT_UNLOCK (task);
365 g_warning ("cannot call set_lock on a running task");
370 * gst_task_set_priority:
372 * @priority: a new priority for @task
374 * Changes the priority of @task to @priority.
376 * Note: try not to depend on task priorities.
383 gst_task_set_priority (GstTask * task, GThreadPriority priority)
385 GstTaskPrivate *priv;
388 g_return_if_fail (GST_IS_TASK (task));
392 GST_OBJECT_LOCK (task);
393 priv->prio_set = TRUE;
394 priv->priority = priority;
395 thread = task->abidata.ABI.thread;
396 if (thread != NULL) {
397 /* if this task already has a thread, we can configure the priority right
398 * away, else we do that when we assign a thread to the task. */
399 g_thread_set_priority (thread, priority);
401 GST_OBJECT_UNLOCK (task);
408 * Get the #GstTaskPool that this task will use for its streaming
413 * Returns: the #GstTaskPool used by @task. gst_object_unref()
419 gst_task_get_pool (GstTask * task)
422 GstTaskPrivate *priv;
424 g_return_val_if_fail (GST_IS_TASK (task), NULL);
428 GST_OBJECT_LOCK (task);
429 result = gst_object_ref (priv->pool);
430 GST_OBJECT_UNLOCK (task);
438 * @pool: a #GstTaskPool
440 * Set @pool as the new GstTaskPool for @task. Any new streaming threads that
441 * will be created by @task will now use @pool.
448 gst_task_set_pool (GstTask * task, GstTaskPool * pool)
451 GstTaskPrivate *priv;
453 g_return_if_fail (GST_IS_TASK (task));
454 g_return_if_fail (GST_IS_TASK_POOL (pool));
458 GST_OBJECT_LOCK (task);
459 if (priv->pool != pool) {
461 priv->pool = gst_object_ref (pool);
464 GST_OBJECT_UNLOCK (task);
467 gst_object_unref (old);
472 * gst_task_set_thread_callbacks:
473 * @task: The #GstTask to use
474 * @callbacks: a #GstTaskThreadCallbacks pointer
475 * @user_data: user data passed to the callbacks
476 * @notify: called when @user_data is no longer referenced
478 * Set callbacks which will be executed when a new thread is needed, the thread
479 * function is entered and left and when the thread is joined.
481 * By default a thread for @task will be created from a default thread pool.
483 * Objects can use custom GThreads or can perform additional configuration of
484 * the threads (such as changing the thread priority) by installing callbacks.
491 gst_task_set_thread_callbacks (GstTask * task,
492 GstTaskThreadCallbacks * callbacks, gpointer user_data,
493 GDestroyNotify notify)
495 GDestroyNotify old_notify;
497 g_return_if_fail (task != NULL);
498 g_return_if_fail (GST_IS_TASK (task));
499 g_return_if_fail (callbacks != NULL);
501 GST_OBJECT_LOCK (task);
502 old_notify = task->priv->thr_notify;
507 old_data = task->priv->thr_user_data;
509 task->priv->thr_user_data = NULL;
510 task->priv->thr_notify = NULL;
511 GST_OBJECT_UNLOCK (task);
513 old_notify (old_data);
515 GST_OBJECT_LOCK (task);
517 task->priv->thr_callbacks = *callbacks;
518 task->priv->thr_user_data = user_data;
519 task->priv->thr_notify = notify;
520 GST_OBJECT_UNLOCK (task);
524 * gst_task_get_state:
525 * @task: The #GstTask to query
527 * Get the current state of the task.
529 * Returns: The #GstTaskState of the task
534 gst_task_get_state (GstTask * task)
538 g_return_val_if_fail (GST_IS_TASK (task), GST_TASK_STOPPED);
540 GST_OBJECT_LOCK (task);
541 result = task->state;
542 GST_OBJECT_UNLOCK (task);
547 /* make sure the task is running and start a thread if it's not.
548 * This function must be called with the task LOCK. */
550 start_task (GstTask * task)
553 GError *error = NULL;
554 GstTaskPrivate *priv;
558 /* new task, We ref before so that it remains alive while
559 * the thread is running. */
560 gst_object_ref (task);
561 /* mark task as running so that a join will wait until we schedule
562 * and exit the task function. */
563 task->running = TRUE;
565 /* push on the thread pool, we remember the original pool because the user
566 * could change it later on and then we join to the wrong pool. */
567 priv->pool_id = gst_object_ref (priv->pool);
569 gst_task_pool_push (priv->pool_id, (GstTaskPoolFunction) gst_task_func,
573 g_warning ("failed to create thread: %s", error->message);
574 g_error_free (error);
582 * gst_task_set_state:
584 * @state: the new task state
586 * Sets the state of @task to @state.
588 * The @task must have a lock associated with it using
589 * gst_task_set_lock() when going to GST_TASK_STARTED or GST_TASK_PAUSED or
590 * this function will return %FALSE.
594 * Returns: %TRUE if the state could be changed.
599 gst_task_set_state (GstTask * task, GstTaskState state)
604 g_return_val_if_fail (GST_IS_TASK (task), FALSE);
606 GST_DEBUG_OBJECT (task, "Changing task %p to state %d", task, state);
608 GST_OBJECT_LOCK (task);
609 if (state != GST_TASK_STOPPED)
610 if (G_UNLIKELY (GST_TASK_GET_LOCK (task) == NULL))
613 /* if the state changed, do our thing */
618 case GST_TASK_STOPPED:
619 /* If the task already has a thread scheduled we don't have to do
621 if (G_UNLIKELY (!task->running))
622 res = start_task (task);
624 case GST_TASK_PAUSED:
625 /* when we are paused, signal to go to the new state */
626 GST_TASK_SIGNAL (task);
628 case GST_TASK_STARTED:
629 /* if we were started, we'll go to the new state after the next
634 GST_OBJECT_UNLOCK (task);
641 GST_WARNING_OBJECT (task, "state %d set on task without a lock", state);
642 GST_OBJECT_UNLOCK (task);
643 g_warning ("task without a lock can't be set to state %d", state);
650 * @task: The #GstTask to start
652 * Starts @task. The @task must have a lock associated with it using
653 * gst_task_set_lock() or this function will return %FALSE.
655 * Returns: %TRUE if the task could be started.
660 gst_task_start (GstTask * task)
662 return gst_task_set_state (task, GST_TASK_STARTED);
667 * @task: The #GstTask to stop
669 * Stops @task. This method merely schedules the task to stop and
670 * will not wait for the task to have completely stopped. Use
671 * gst_task_join() to stop and wait for completion.
673 * Returns: %TRUE if the task could be stopped.
678 gst_task_stop (GstTask * task)
680 return gst_task_set_state (task, GST_TASK_STOPPED);
685 * @task: The #GstTask to pause
687 * Pauses @task. This method can also be called on a task in the
688 * stopped state, in which case a thread will be started and will remain
689 * in the paused state. This function does not wait for the task to complete
692 * Returns: %TRUE if the task could be paused.
697 gst_task_pause (GstTask * task)
699 return gst_task_set_state (task, GST_TASK_PAUSED);
704 * @task: The #GstTask to join
706 * Joins @task. After this call, it is safe to unref the task
707 * and clean up the lock set with gst_task_set_lock().
709 * The task will automatically be stopped with this call.
711 * This function cannot be called from within a task function as this
712 * would cause a deadlock. The function will detect this and print a
715 * Returns: %TRUE if the task could be joined.
720 gst_task_join (GstTask * task)
723 GstTaskPrivate *priv;
725 GstTaskPool *pool = NULL;
729 g_return_val_if_fail (GST_IS_TASK (task), FALSE);
731 tself = g_thread_self ();
733 GST_DEBUG_OBJECT (task, "Joining task %p, thread %p", task, tself);
735 /* we don't use a real thread join here because we are using
737 GST_OBJECT_LOCK (task);
738 if (G_UNLIKELY (tself == task->abidata.ABI.thread))
740 task->state = GST_TASK_STOPPED;
741 /* signal the state change for when it was blocked in PAUSED. */
742 GST_TASK_SIGNAL (task);
743 /* we set the running flag when pushing the task on the thread pool.
744 * This means that the task function might not be called when we try
745 * to join it here. */
746 while (G_LIKELY (task->running))
747 GST_TASK_WAIT (task);
748 /* clean the thread */
749 task->abidata.ABI.thread = NULL;
750 /* get the id and pool to join */
751 pool = priv->pool_id;
753 priv->pool_id = NULL;
755 GST_OBJECT_UNLOCK (task);
759 gst_task_pool_join (pool, id);
760 gst_object_unref (pool);
763 GST_DEBUG_OBJECT (task, "Joined task %p", task);
770 GST_WARNING_OBJECT (task, "trying to join task from its thread");
771 GST_OBJECT_UNLOCK (task);
772 g_warning ("\nTrying to join task %p from its thread would deadlock.\n"
773 "You cannot change the state of an element from its streaming\n"
774 "thread. Use g_idle_add() or post a GstMessage on the bus to\n"
775 "schedule the state change from the main thread.\n", task);