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_class_init (GstTaskClass * klass);
96 static void gst_task_init (GstTask * task);
97 static void gst_task_finalize (GObject * object);
99 static void gst_task_func (GstTask * task);
101 static GStaticMutex pool_lock = G_STATIC_MUTEX_INIT;
105 GST_DEBUG_CATEGORY_INIT (task_debug, "task", 0, "Processing tasks"); \
108 G_DEFINE_TYPE_WITH_CODE (GstTask, gst_task, GST_TYPE_OBJECT, _do_init);
111 init_klass_pool (GstTaskClass * klass)
113 g_static_mutex_lock (&pool_lock);
115 gst_task_pool_cleanup (klass->pool);
116 gst_object_unref (klass->pool);
118 klass->pool = gst_task_pool_new ();
119 gst_task_pool_prepare (klass->pool, NULL);
120 g_static_mutex_unlock (&pool_lock);
124 gst_task_class_init (GstTaskClass * klass)
126 GObjectClass *gobject_class;
128 gobject_class = (GObjectClass *) klass;
130 g_type_class_add_private (klass, sizeof (GstTaskPrivate));
132 gobject_class->finalize = gst_task_finalize;
134 init_klass_pool (klass);
138 gst_task_init (GstTask * task)
142 klass = GST_TASK_GET_CLASS (task);
144 task->priv = GST_TASK_GET_PRIVATE (task);
145 task->running = FALSE;
146 task->abidata.ABI.thread = NULL;
148 task->cond = g_cond_new ();
149 task->state = GST_TASK_STOPPED;
150 task->priv->prio_set = FALSE;
152 /* use the default klass pool for this task, users can
153 * override this later */
154 g_static_mutex_lock (&pool_lock);
155 task->priv->pool = gst_object_ref (klass->pool);
156 g_static_mutex_unlock (&pool_lock);
160 gst_task_finalize (GObject * object)
162 GstTask *task = GST_TASK (object);
163 GstTaskPrivate *priv = task->priv;
165 GST_DEBUG ("task %p finalize", task);
167 if (priv->thr_notify)
168 priv->thr_notify (priv->thr_user_data);
169 priv->thr_notify = NULL;
170 priv->thr_user_data = NULL;
172 gst_object_unref (priv->pool);
174 /* task thread cannot be running here since it holds a ref
175 * to the task so that the finalize could not have happened */
176 g_cond_free (task->cond);
179 G_OBJECT_CLASS (gst_task_parent_class)->finalize (object);
183 gst_task_func (GstTask * task)
185 GStaticRecMutex *lock;
187 GstTaskPrivate *priv;
191 tself = g_thread_self ();
193 GST_DEBUG ("Entering task %p, thread %p", task, tself);
195 /* we have to grab the lock to get the mutex. We also
196 * mark our state running so that nobody can mess with
198 GST_OBJECT_LOCK (task);
199 if (task->state == GST_TASK_STOPPED)
201 lock = GST_TASK_GET_LOCK (task);
202 if (G_UNLIKELY (lock == NULL))
204 task->abidata.ABI.thread = tself;
205 /* only update the priority when it was changed */
207 g_thread_set_priority (tself, priv->priority);
208 GST_OBJECT_UNLOCK (task);
210 /* fire the enter_thread callback when we need to */
211 if (priv->thr_callbacks.enter_thread)
212 priv->thr_callbacks.enter_thread (task, tself, priv->thr_user_data);
214 /* locking order is TASK_LOCK, LOCK */
215 g_static_rec_mutex_lock (lock);
216 GST_OBJECT_LOCK (task);
217 while (G_LIKELY (task->state != GST_TASK_STOPPED)) {
218 while (G_UNLIKELY (task->state == GST_TASK_PAUSED)) {
221 t = g_static_rec_mutex_unlock_full (lock);
223 g_warning ("wrong STREAM_LOCK count %d", t);
225 GST_TASK_SIGNAL (task);
226 GST_TASK_WAIT (task);
227 GST_OBJECT_UNLOCK (task);
228 /* locking order.. */
230 g_static_rec_mutex_lock_full (lock, t);
232 GST_OBJECT_LOCK (task);
233 if (G_UNLIKELY (task->state == GST_TASK_STOPPED))
236 GST_OBJECT_UNLOCK (task);
238 task->func (task->data);
240 GST_OBJECT_LOCK (task);
243 GST_OBJECT_UNLOCK (task);
244 g_static_rec_mutex_unlock (lock);
246 GST_OBJECT_LOCK (task);
247 task->abidata.ABI.thread = NULL;
250 if (priv->thr_callbacks.leave_thread) {
251 /* fire the leave_thread callback when we need to. We need to do this before
252 * we signal the task and with the task lock released. */
253 GST_OBJECT_UNLOCK (task);
254 priv->thr_callbacks.leave_thread (task, tself, priv->thr_user_data);
255 GST_OBJECT_LOCK (task);
257 /* restore normal priority when releasing back into the pool, we will not
258 * touch the priority when a custom callback has been installed. */
259 g_thread_set_priority (tself, G_THREAD_PRIORITY_NORMAL);
261 /* now we allow messing with the lock again by setting the running flag to
262 * FALSE. Together with the SIGNAL this is the sign for the _join() to
264 * Note that we still have not dropped the final ref on the task. We could
265 * check here if there is a pending join() going on and drop the last ref
266 * before releasing the lock as we can be sure that a ref is held by the
267 * caller of the join(). */
268 task->running = FALSE;
269 GST_TASK_SIGNAL (task);
270 GST_OBJECT_UNLOCK (task);
272 GST_DEBUG ("Exit task %p, thread %p", task, g_thread_self ());
274 gst_object_unref (task);
279 g_warning ("starting task without a lock");
285 * gst_task_cleanup_all:
287 * Wait for all tasks to be stopped. This is mainly used internally
288 * to ensure proper cleanup of internal data structures in test suites.
293 gst_task_cleanup_all (void)
297 if ((klass = g_type_class_peek (GST_TYPE_TASK))) {
298 init_klass_pool (klass);
304 * @func: The #GstTaskFunction to use
305 * @data: User data to pass to @func
307 * Create a new Task that will repeatedly call the provided @func
308 * with @data as a parameter. Typically the task will run in
311 * The function cannot be changed after the task has been created. You
312 * must create a new #GstTask to change the function.
314 * This function will not yet create and start a thread. Use gst_task_start() or
315 * gst_task_pause() to create and start the GThread.
317 * Before the task can be used, a #GStaticRecMutex must be configured using the
318 * gst_task_set_lock() function. This lock will always be acquired while
321 * Returns: A new #GstTask.
326 gst_task_create (GstTaskFunction func, gpointer data)
330 task = g_object_newv (GST_TYPE_TASK, 0, NULL);
334 GST_DEBUG ("Created task %p", task);
341 * @task: The #GstTask to use
342 * @mutex: The #GMutex to use
344 * Set the mutex used by the task. The mutex will be acquired before
345 * calling the #GstTaskFunction.
347 * This function has to be called before calling gst_task_pause() or
353 gst_task_set_lock (GstTask * task, GStaticRecMutex * mutex)
355 GST_OBJECT_LOCK (task);
356 if (G_UNLIKELY (task->running))
358 GST_TASK_GET_LOCK (task) = mutex;
359 GST_OBJECT_UNLOCK (task);
366 GST_OBJECT_UNLOCK (task);
367 g_warning ("cannot call set_lock on a running task");
372 * gst_task_set_priority:
374 * @priority: a new priority for @task
376 * Changes the priority of @task to @priority.
378 * Note: try not to depend on task priorities.
385 gst_task_set_priority (GstTask * task, GThreadPriority priority)
387 GstTaskPrivate *priv;
390 g_return_if_fail (GST_IS_TASK (task));
394 GST_OBJECT_LOCK (task);
395 priv->prio_set = TRUE;
396 priv->priority = priority;
397 thread = task->abidata.ABI.thread;
398 if (thread != NULL) {
399 /* if this task already has a thread, we can configure the priority right
400 * away, else we do that when we assign a thread to the task. */
401 g_thread_set_priority (thread, priority);
403 GST_OBJECT_UNLOCK (task);
410 * Get the #GstTaskPool that this task will use for its streaming
415 * Returns: the #GstTaskPool used by @task. gst_object_unref()
421 gst_task_get_pool (GstTask * task)
424 GstTaskPrivate *priv;
426 g_return_val_if_fail (GST_IS_TASK (task), NULL);
430 GST_OBJECT_LOCK (task);
431 result = gst_object_ref (priv->pool);
432 GST_OBJECT_UNLOCK (task);
440 * @pool: a #GstTaskPool
442 * Set @pool as the new GstTaskPool for @task. Any new streaming threads that
443 * will be created by @task will now use @pool.
450 gst_task_set_pool (GstTask * task, GstTaskPool * pool)
453 GstTaskPrivate *priv;
455 g_return_if_fail (GST_IS_TASK (task));
456 g_return_if_fail (GST_IS_TASK_POOL (pool));
460 GST_OBJECT_LOCK (task);
461 if (priv->pool != pool) {
463 priv->pool = gst_object_ref (pool);
466 GST_OBJECT_UNLOCK (task);
469 gst_object_unref (old);
474 * gst_task_set_thread_callbacks:
475 * @task: The #GstTask to use
476 * @callbacks: a #GstTaskThreadCallbacks pointer
477 * @user_data: user data passed to the callbacks
478 * @notify: called when @user_data is no longer referenced
480 * Set callbacks which will be executed when a new thread is needed, the thread
481 * function is entered and left and when the thread is joined.
483 * By default a thread for @task will be created from a default thread pool.
485 * Objects can use custom GThreads or can perform additional configuration of
486 * the threads (such as changing the thread priority) by installing callbacks.
493 gst_task_set_thread_callbacks (GstTask * task,
494 GstTaskThreadCallbacks * callbacks, gpointer user_data,
495 GDestroyNotify notify)
497 GDestroyNotify old_notify;
499 g_return_if_fail (task != NULL);
500 g_return_if_fail (GST_IS_TASK (task));
501 g_return_if_fail (callbacks != NULL);
503 GST_OBJECT_LOCK (task);
504 old_notify = task->priv->thr_notify;
509 old_data = task->priv->thr_user_data;
511 task->priv->thr_user_data = NULL;
512 task->priv->thr_notify = NULL;
513 GST_OBJECT_UNLOCK (task);
515 old_notify (old_data);
517 GST_OBJECT_LOCK (task);
519 task->priv->thr_callbacks = *callbacks;
520 task->priv->thr_user_data = user_data;
521 task->priv->thr_notify = notify;
522 GST_OBJECT_UNLOCK (task);
526 * gst_task_get_state:
527 * @task: The #GstTask to query
529 * Get the current state of the task.
531 * Returns: The #GstTaskState of the task
536 gst_task_get_state (GstTask * task)
540 g_return_val_if_fail (GST_IS_TASK (task), GST_TASK_STOPPED);
542 GST_OBJECT_LOCK (task);
543 result = task->state;
544 GST_OBJECT_UNLOCK (task);
549 /* make sure the task is running and start a thread if it's not.
550 * This function must be called with the task LOCK. */
552 start_task (GstTask * task)
555 GError *error = NULL;
556 GstTaskPrivate *priv;
560 /* new task, We ref before so that it remains alive while
561 * the thread is running. */
562 gst_object_ref (task);
563 /* mark task as running so that a join will wait until we schedule
564 * and exit the task function. */
565 task->running = TRUE;
567 /* push on the thread pool, we remember the original pool because the user
568 * could change it later on and then we join to the wrong pool. */
569 priv->pool_id = gst_object_ref (priv->pool);
571 gst_task_pool_push (priv->pool_id, (GstTaskPoolFunction) gst_task_func,
575 g_warning ("failed to create thread: %s", error->message);
576 g_error_free (error);
584 * gst_task_set_state:
586 * @state: the new task state
588 * Sets the state of @task to @state.
590 * The @task must have a lock associated with it using
591 * gst_task_set_lock() when going to GST_TASK_STARTED or GST_TASK_PAUSED or
592 * this function will return %FALSE.
596 * Returns: %TRUE if the state could be changed.
601 gst_task_set_state (GstTask * task, GstTaskState state)
606 g_return_val_if_fail (GST_IS_TASK (task), FALSE);
608 GST_DEBUG_OBJECT (task, "Changing task %p to state %d", task, state);
610 GST_OBJECT_LOCK (task);
611 if (state != GST_TASK_STOPPED)
612 if (G_UNLIKELY (GST_TASK_GET_LOCK (task) == NULL))
615 /* if the state changed, do our thing */
620 case GST_TASK_STOPPED:
621 /* If the task already has a thread scheduled we don't have to do
623 if (G_UNLIKELY (!task->running))
624 res = start_task (task);
626 case GST_TASK_PAUSED:
627 /* when we are paused, signal to go to the new state */
628 GST_TASK_SIGNAL (task);
630 case GST_TASK_STARTED:
631 /* if we were started, we'll go to the new state after the next
636 GST_OBJECT_UNLOCK (task);
643 GST_WARNING_OBJECT (task, "state %d set on task without a lock", state);
644 GST_OBJECT_UNLOCK (task);
645 g_warning ("task without a lock can't be set to state %d", state);
652 * @task: The #GstTask to start
654 * Starts @task. The @task must have a lock associated with it using
655 * gst_task_set_lock() or this function will return %FALSE.
657 * Returns: %TRUE if the task could be started.
662 gst_task_start (GstTask * task)
664 return gst_task_set_state (task, GST_TASK_STARTED);
669 * @task: The #GstTask to stop
671 * Stops @task. This method merely schedules the task to stop and
672 * will not wait for the task to have completely stopped. Use
673 * gst_task_join() to stop and wait for completion.
675 * Returns: %TRUE if the task could be stopped.
680 gst_task_stop (GstTask * task)
682 return gst_task_set_state (task, GST_TASK_STOPPED);
687 * @task: The #GstTask to pause
689 * Pauses @task. This method can also be called on a task in the
690 * stopped state, in which case a thread will be started and will remain
691 * in the paused state. This function does not wait for the task to complete
694 * Returns: %TRUE if the task could be paused.
699 gst_task_pause (GstTask * task)
701 return gst_task_set_state (task, GST_TASK_PAUSED);
706 * @task: The #GstTask to join
708 * Joins @task. After this call, it is safe to unref the task
709 * and clean up the lock set with gst_task_set_lock().
711 * The task will automatically be stopped with this call.
713 * This function cannot be called from within a task function as this
714 * would cause a deadlock. The function will detect this and print a
717 * Returns: %TRUE if the task could be joined.
722 gst_task_join (GstTask * task)
725 GstTaskPrivate *priv;
727 GstTaskPool *pool = NULL;
731 g_return_val_if_fail (GST_IS_TASK (task), FALSE);
733 tself = g_thread_self ();
735 GST_DEBUG_OBJECT (task, "Joining task %p, thread %p", task, tself);
737 /* we don't use a real thread join here because we are using
739 GST_OBJECT_LOCK (task);
740 if (G_UNLIKELY (tself == task->abidata.ABI.thread))
742 task->state = GST_TASK_STOPPED;
743 /* signal the state change for when it was blocked in PAUSED. */
744 GST_TASK_SIGNAL (task);
745 /* we set the running flag when pushing the task on the thread pool.
746 * This means that the task function might not be called when we try
747 * to join it here. */
748 while (G_LIKELY (task->running))
749 GST_TASK_WAIT (task);
750 /* clean the thread */
751 task->abidata.ABI.thread = NULL;
752 /* get the id and pool to join */
753 pool = priv->pool_id;
755 priv->pool_id = NULL;
757 GST_OBJECT_UNLOCK (task);
761 gst_task_pool_join (pool, id);
762 gst_object_unref (pool);
765 GST_DEBUG_OBJECT (task, "Joined task %p", task);
772 GST_WARNING_OBJECT (task, "trying to join task from its thread");
773 GST_OBJECT_UNLOCK (task);
774 g_warning ("\nTrying to join task %p from its thread would deadlock.\n"
775 "You cannot change the state of an element from its streaming\n"
776 "thread. Use g_idle_add() or post a GstMessage on the bus to\n"
777 "schedule the state change from the main thread.\n", task);