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 * 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 #include "gst_private.h"
78 #ifdef HAVE_SYS_PRCTL_H
79 #include <sys/prctl.h>
82 GST_DEBUG_CATEGORY_STATIC (task_debug);
83 #define GST_CAT_DEFAULT (task_debug)
85 #define GST_TASK_GET_PRIVATE(obj) \
86 (G_TYPE_INSTANCE_GET_PRIVATE ((obj), GST_TYPE_TASK, GstTaskPrivate))
88 struct _GstTaskPrivate
90 /* callbacks for managing the thread of this task */
91 GstTaskThreadCallbacks thr_callbacks;
92 gpointer thr_user_data;
93 GDestroyNotify thr_notify;
96 GThreadPriority priority;
101 /* remember the pool and id that is currently running. */
103 GstTaskPool *pool_id;
106 static void gst_task_finalize (GObject * object);
108 static void gst_task_func (GstTask * task);
110 static GStaticMutex pool_lock = G_STATIC_MUTEX_INIT;
114 GST_DEBUG_CATEGORY_INIT (task_debug, "task", 0, "Processing tasks"); \
117 G_DEFINE_TYPE_WITH_CODE (GstTask, gst_task, GST_TYPE_OBJECT, _do_init);
120 init_klass_pool (GstTaskClass * klass)
122 g_static_mutex_lock (&pool_lock);
124 gst_task_pool_cleanup (klass->pool);
125 gst_object_unref (klass->pool);
127 klass->pool = gst_task_pool_new ();
128 gst_task_pool_prepare (klass->pool, NULL);
129 g_static_mutex_unlock (&pool_lock);
133 gst_task_class_init (GstTaskClass * klass)
135 GObjectClass *gobject_class;
137 gobject_class = (GObjectClass *) klass;
139 g_type_class_add_private (klass, sizeof (GstTaskPrivate));
141 gobject_class->finalize = gst_task_finalize;
143 init_klass_pool (klass);
147 gst_task_init (GstTask * task)
151 klass = GST_TASK_GET_CLASS (task);
153 task->priv = GST_TASK_GET_PRIVATE (task);
154 task->running = FALSE;
155 task->abidata.ABI.thread = NULL;
157 task->cond = g_cond_new ();
158 task->state = GST_TASK_STOPPED;
159 task->priv->prio_set = FALSE;
161 /* use the default klass pool for this task, users can
162 * override this later */
163 g_static_mutex_lock (&pool_lock);
164 task->priv->pool = gst_object_ref (klass->pool);
165 g_static_mutex_unlock (&pool_lock);
169 gst_task_finalize (GObject * object)
171 GstTask *task = GST_TASK (object);
172 GstTaskPrivate *priv = task->priv;
174 GST_DEBUG ("task %p finalize", task);
176 if (priv->thr_notify)
177 priv->thr_notify (priv->thr_user_data);
178 priv->thr_notify = NULL;
179 priv->thr_user_data = NULL;
181 gst_object_unref (priv->pool);
183 /* task thread cannot be running here since it holds a ref
184 * to the task so that the finalize could not have happened */
185 g_cond_free (task->cond);
188 G_OBJECT_CLASS (gst_task_parent_class)->finalize (object);
191 /* should be called with the object LOCK */
193 gst_task_configure_name (GstTask * task)
195 #ifdef HAVE_SYS_PRCTL_H
197 gchar thread_name[17] = { 0, };
199 name = GST_OBJECT_NAME (task);
201 /* set the thread name to something easily identifiable */
202 if (!snprintf (thread_name, 17, "%s", GST_STR_NULL (name))) {
203 GST_DEBUG_OBJECT (task, "Could not create thread name for '%s'", name);
205 GST_DEBUG_OBJECT (task, "Setting thread name to '%s'", thread_name);
206 if (prctl (PR_SET_NAME, (unsigned long int) thread_name, 0, 0, 0))
207 GST_DEBUG_OBJECT (task, "Failed to set thread name");
213 gst_task_func (GstTask * task)
215 GStaticRecMutex *lock;
217 GstTaskPrivate *priv;
221 tself = g_thread_self ();
223 GST_DEBUG ("Entering task %p, thread %p", task, tself);
225 /* we have to grab the lock to get the mutex. We also
226 * mark our state running so that nobody can mess with
228 GST_OBJECT_LOCK (task);
229 if (task->state == GST_TASK_STOPPED)
231 lock = GST_TASK_GET_LOCK (task);
232 if (G_UNLIKELY (lock == NULL))
234 task->abidata.ABI.thread = tself;
235 /* only update the priority when it was changed */
237 g_thread_set_priority (tself, priv->priority);
238 GST_OBJECT_UNLOCK (task);
240 /* fire the enter_thread callback when we need to */
241 if (priv->thr_callbacks.enter_thread)
242 priv->thr_callbacks.enter_thread (task, tself, priv->thr_user_data);
244 /* locking order is TASK_LOCK, LOCK */
245 g_static_rec_mutex_lock (lock);
246 GST_OBJECT_LOCK (task);
247 /* configure the thread name now */
248 gst_task_configure_name (task);
250 while (G_LIKELY (task->state != GST_TASK_STOPPED)) {
251 while (G_UNLIKELY (task->state == GST_TASK_PAUSED)) {
254 t = g_static_rec_mutex_unlock_full (lock);
256 g_warning ("wrong STREAM_LOCK count %d", t);
258 GST_TASK_SIGNAL (task);
259 GST_TASK_WAIT (task);
260 GST_OBJECT_UNLOCK (task);
261 /* locking order.. */
263 g_static_rec_mutex_lock_full (lock, t);
265 GST_OBJECT_LOCK (task);
266 if (G_UNLIKELY (task->state == GST_TASK_STOPPED))
269 GST_OBJECT_UNLOCK (task);
271 task->func (task->data);
273 GST_OBJECT_LOCK (task);
276 GST_OBJECT_UNLOCK (task);
277 g_static_rec_mutex_unlock (lock);
279 GST_OBJECT_LOCK (task);
280 task->abidata.ABI.thread = NULL;
283 if (priv->thr_callbacks.leave_thread) {
284 /* fire the leave_thread callback when we need to. We need to do this before
285 * we signal the task and with the task lock released. */
286 GST_OBJECT_UNLOCK (task);
287 priv->thr_callbacks.leave_thread (task, tself, priv->thr_user_data);
288 GST_OBJECT_LOCK (task);
290 /* restore normal priority when releasing back into the pool, we will not
291 * touch the priority when a custom callback has been installed. */
292 g_thread_set_priority (tself, G_THREAD_PRIORITY_NORMAL);
294 /* now we allow messing with the lock again by setting the running flag to
295 * FALSE. Together with the SIGNAL this is the sign for the _join() to
297 * Note that we still have not dropped the final ref on the task. We could
298 * check here if there is a pending join() going on and drop the last ref
299 * before releasing the lock as we can be sure that a ref is held by the
300 * caller of the join(). */
301 task->running = FALSE;
302 GST_TASK_SIGNAL (task);
303 GST_OBJECT_UNLOCK (task);
305 GST_DEBUG ("Exit task %p, thread %p", task, g_thread_self ());
307 gst_object_unref (task);
312 g_warning ("starting task without a lock");
318 * gst_task_cleanup_all:
320 * Wait for all tasks to be stopped. This is mainly used internally
321 * to ensure proper cleanup of internal data structures in test suites.
326 gst_task_cleanup_all (void)
330 if ((klass = g_type_class_peek (GST_TYPE_TASK))) {
331 init_klass_pool (klass);
337 * @func: The #GstTaskFunction to use
338 * @data: User data to pass to @func
340 * Create a new Task that will repeatedly call the provided @func
341 * with @data as a parameter. Typically the task will run in
344 * The function cannot be changed after the task has been created. You
345 * must create a new #GstTask to change the function.
347 * This function will not yet create and start a thread. Use gst_task_start() or
348 * gst_task_pause() to create and start the GThread.
350 * Before the task can be used, a #GStaticRecMutex must be configured using the
351 * gst_task_set_lock() function. This lock will always be acquired while
354 * Returns: A new #GstTask.
359 gst_task_create (GstTaskFunction func, gpointer data)
363 task = g_object_newv (GST_TYPE_TASK, 0, NULL);
367 GST_DEBUG ("Created task %p", task);
374 * @task: The #GstTask to use
375 * @mutex: The #GMutex to use
377 * Set the mutex used by the task. The mutex will be acquired before
378 * calling the #GstTaskFunction.
380 * This function has to be called before calling gst_task_pause() or
386 gst_task_set_lock (GstTask * task, GStaticRecMutex * mutex)
388 GST_OBJECT_LOCK (task);
389 if (G_UNLIKELY (task->running))
391 GST_TASK_GET_LOCK (task) = mutex;
392 GST_OBJECT_UNLOCK (task);
399 GST_OBJECT_UNLOCK (task);
400 g_warning ("cannot call set_lock on a running task");
405 * gst_task_set_priority:
407 * @priority: a new priority for @task
409 * Changes the priority of @task to @priority.
411 * Note: try not to depend on task priorities.
418 gst_task_set_priority (GstTask * task, GThreadPriority priority)
420 GstTaskPrivate *priv;
423 g_return_if_fail (GST_IS_TASK (task));
427 GST_OBJECT_LOCK (task);
428 priv->prio_set = TRUE;
429 priv->priority = priority;
430 thread = task->abidata.ABI.thread;
431 if (thread != NULL) {
432 /* if this task already has a thread, we can configure the priority right
433 * away, else we do that when we assign a thread to the task. */
434 g_thread_set_priority (thread, priority);
436 GST_OBJECT_UNLOCK (task);
443 * Get the #GstTaskPool that this task will use for its streaming
448 * Returns: the #GstTaskPool used by @task. gst_object_unref()
454 gst_task_get_pool (GstTask * task)
457 GstTaskPrivate *priv;
459 g_return_val_if_fail (GST_IS_TASK (task), NULL);
463 GST_OBJECT_LOCK (task);
464 result = gst_object_ref (priv->pool);
465 GST_OBJECT_UNLOCK (task);
473 * @pool: a #GstTaskPool
475 * Set @pool as the new GstTaskPool for @task. Any new streaming threads that
476 * will be created by @task will now use @pool.
483 gst_task_set_pool (GstTask * task, GstTaskPool * pool)
486 GstTaskPrivate *priv;
488 g_return_if_fail (GST_IS_TASK (task));
489 g_return_if_fail (GST_IS_TASK_POOL (pool));
493 GST_OBJECT_LOCK (task);
494 if (priv->pool != pool) {
496 priv->pool = gst_object_ref (pool);
499 GST_OBJECT_UNLOCK (task);
502 gst_object_unref (old);
507 * gst_task_set_thread_callbacks:
508 * @task: The #GstTask to use
509 * @callbacks: a #GstTaskThreadCallbacks pointer
510 * @user_data: user data passed to the callbacks
511 * @notify: called when @user_data is no longer referenced
513 * Set callbacks which will be executed when a new thread is needed, the thread
514 * function is entered and left and when the thread is joined.
516 * By default a thread for @task will be created from a default thread pool.
518 * Objects can use custom GThreads or can perform additional configuration of
519 * the threads (such as changing the thread priority) by installing callbacks.
526 gst_task_set_thread_callbacks (GstTask * task,
527 GstTaskThreadCallbacks * callbacks, gpointer user_data,
528 GDestroyNotify notify)
530 GDestroyNotify old_notify;
532 g_return_if_fail (task != NULL);
533 g_return_if_fail (GST_IS_TASK (task));
534 g_return_if_fail (callbacks != NULL);
536 GST_OBJECT_LOCK (task);
537 old_notify = task->priv->thr_notify;
542 old_data = task->priv->thr_user_data;
544 task->priv->thr_user_data = NULL;
545 task->priv->thr_notify = NULL;
546 GST_OBJECT_UNLOCK (task);
548 old_notify (old_data);
550 GST_OBJECT_LOCK (task);
552 task->priv->thr_callbacks = *callbacks;
553 task->priv->thr_user_data = user_data;
554 task->priv->thr_notify = notify;
555 GST_OBJECT_UNLOCK (task);
559 * gst_task_get_state:
560 * @task: The #GstTask to query
562 * Get the current state of the task.
564 * Returns: The #GstTaskState of the task
569 gst_task_get_state (GstTask * task)
573 g_return_val_if_fail (GST_IS_TASK (task), GST_TASK_STOPPED);
575 GST_OBJECT_LOCK (task);
576 result = task->state;
577 GST_OBJECT_UNLOCK (task);
582 /* make sure the task is running and start a thread if it's not.
583 * This function must be called with the task LOCK. */
585 start_task (GstTask * task)
588 GError *error = NULL;
589 GstTaskPrivate *priv;
593 /* new task, We ref before so that it remains alive while
594 * the thread is running. */
595 gst_object_ref (task);
596 /* mark task as running so that a join will wait until we schedule
597 * and exit the task function. */
598 task->running = TRUE;
600 /* push on the thread pool, we remember the original pool because the user
601 * could change it later on and then we join to the wrong pool. */
602 priv->pool_id = gst_object_ref (priv->pool);
604 gst_task_pool_push (priv->pool_id, (GstTaskPoolFunction) gst_task_func,
608 g_warning ("failed to create thread: %s", error->message);
609 g_error_free (error);
617 * gst_task_set_state:
619 * @state: the new task state
621 * Sets the state of @task to @state.
623 * The @task must have a lock associated with it using
624 * gst_task_set_lock() when going to GST_TASK_STARTED or GST_TASK_PAUSED or
625 * this function will return %FALSE.
629 * Returns: %TRUE if the state could be changed.
634 gst_task_set_state (GstTask * task, GstTaskState state)
639 g_return_val_if_fail (GST_IS_TASK (task), FALSE);
641 GST_DEBUG_OBJECT (task, "Changing task %p to state %d", task, state);
643 GST_OBJECT_LOCK (task);
644 if (state != GST_TASK_STOPPED)
645 if (G_UNLIKELY (GST_TASK_GET_LOCK (task) == NULL))
648 /* if the state changed, do our thing */
653 case GST_TASK_STOPPED:
654 /* If the task already has a thread scheduled we don't have to do
656 if (G_UNLIKELY (!task->running))
657 res = start_task (task);
659 case GST_TASK_PAUSED:
660 /* when we are paused, signal to go to the new state */
661 GST_TASK_SIGNAL (task);
663 case GST_TASK_STARTED:
664 /* if we were started, we'll go to the new state after the next
669 GST_OBJECT_UNLOCK (task);
676 GST_WARNING_OBJECT (task, "state %d set on task without a lock", state);
677 GST_OBJECT_UNLOCK (task);
678 g_warning ("task without a lock can't be set to state %d", state);
685 * @task: The #GstTask to start
687 * Starts @task. The @task must have a lock associated with it using
688 * gst_task_set_lock() or this function will return %FALSE.
690 * Returns: %TRUE if the task could be started.
695 gst_task_start (GstTask * task)
697 return gst_task_set_state (task, GST_TASK_STARTED);
702 * @task: The #GstTask to stop
704 * Stops @task. This method merely schedules the task to stop and
705 * will not wait for the task to have completely stopped. Use
706 * gst_task_join() to stop and wait for completion.
708 * Returns: %TRUE if the task could be stopped.
713 gst_task_stop (GstTask * task)
715 return gst_task_set_state (task, GST_TASK_STOPPED);
720 * @task: The #GstTask to pause
722 * Pauses @task. This method can also be called on a task in the
723 * stopped state, in which case a thread will be started and will remain
724 * in the paused state. This function does not wait for the task to complete
727 * Returns: %TRUE if the task could be paused.
732 gst_task_pause (GstTask * task)
734 return gst_task_set_state (task, GST_TASK_PAUSED);
739 * @task: The #GstTask to join
741 * Joins @task. After this call, it is safe to unref the task
742 * and clean up the lock set with gst_task_set_lock().
744 * The task will automatically be stopped with this call.
746 * This function cannot be called from within a task function as this
747 * would cause a deadlock. The function will detect this and print a
750 * Returns: %TRUE if the task could be joined.
755 gst_task_join (GstTask * task)
758 GstTaskPrivate *priv;
760 GstTaskPool *pool = NULL;
764 g_return_val_if_fail (GST_IS_TASK (task), FALSE);
766 tself = g_thread_self ();
768 GST_DEBUG_OBJECT (task, "Joining task %p, thread %p", task, tself);
770 /* we don't use a real thread join here because we are using
772 GST_OBJECT_LOCK (task);
773 if (G_UNLIKELY (tself == task->abidata.ABI.thread))
775 task->state = GST_TASK_STOPPED;
776 /* signal the state change for when it was blocked in PAUSED. */
777 GST_TASK_SIGNAL (task);
778 /* we set the running flag when pushing the task on the thread pool.
779 * This means that the task function might not be called when we try
780 * to join it here. */
781 while (G_LIKELY (task->running))
782 GST_TASK_WAIT (task);
783 /* clean the thread */
784 task->abidata.ABI.thread = NULL;
785 /* get the id and pool to join */
786 pool = priv->pool_id;
788 priv->pool_id = NULL;
790 GST_OBJECT_UNLOCK (task);
794 gst_task_pool_join (pool, id);
795 gst_object_unref (pool);
798 GST_DEBUG_OBJECT (task, "Joined task %p", task);
805 GST_WARNING_OBJECT (task, "trying to join task from its thread");
806 GST_OBJECT_UNLOCK (task);
807 g_warning ("\nTrying to join task %p from its thread would deadlock.\n"
808 "You cannot change the state of an element from its streaming\n"
809 "thread. Use g_idle_add() or post a GstMessage on the bus to\n"
810 "schedule the state change from the main thread.\n", task);