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 #ifdef HAVE_SYS_PRCTL_H
72 #include <sys/prctl.h>
75 GST_DEBUG_CATEGORY_STATIC (task_debug);
76 #define GST_CAT_DEFAULT (task_debug)
78 #define GST_TASK_GET_PRIVATE(obj) \
79 (G_TYPE_INSTANCE_GET_PRIVATE ((obj), GST_TYPE_TASK, GstTaskPrivate))
81 struct _GstTaskPrivate
83 /* callbacks for managing the thread of this task */
84 GstTaskThreadCallbacks thr_callbacks;
85 gpointer thr_user_data;
86 GDestroyNotify thr_notify;
89 GThreadPriority priority;
94 /* remember the pool and id that is currently running. */
99 static void gst_task_finalize (GObject * object);
101 static void gst_task_func (GstTask * task);
103 static GStaticMutex pool_lock = G_STATIC_MUTEX_INIT;
107 GST_DEBUG_CATEGORY_INIT (task_debug, "task", 0, "Processing tasks"); \
110 G_DEFINE_TYPE_WITH_CODE (GstTask, gst_task, GST_TYPE_OBJECT, _do_init);
113 init_klass_pool (GstTaskClass * klass)
115 g_static_mutex_lock (&pool_lock);
117 gst_task_pool_cleanup (klass->pool);
118 gst_object_unref (klass->pool);
120 klass->pool = gst_task_pool_new ();
121 gst_task_pool_prepare (klass->pool, NULL);
122 g_static_mutex_unlock (&pool_lock);
126 gst_task_class_init (GstTaskClass * klass)
128 GObjectClass *gobject_class;
130 gobject_class = (GObjectClass *) klass;
132 g_type_class_add_private (klass, sizeof (GstTaskPrivate));
134 gobject_class->finalize = gst_task_finalize;
136 init_klass_pool (klass);
140 gst_task_init (GstTask * task)
144 klass = GST_TASK_GET_CLASS (task);
146 task->priv = GST_TASK_GET_PRIVATE (task);
147 task->running = FALSE;
148 task->abidata.ABI.thread = NULL;
150 task->cond = g_cond_new ();
151 task->state = GST_TASK_STOPPED;
152 task->priv->prio_set = FALSE;
154 /* use the default klass pool for this task, users can
155 * override this later */
156 g_static_mutex_lock (&pool_lock);
157 task->priv->pool = gst_object_ref (klass->pool);
158 g_static_mutex_unlock (&pool_lock);
162 gst_task_finalize (GObject * object)
164 GstTask *task = GST_TASK (object);
165 GstTaskPrivate *priv = task->priv;
167 GST_DEBUG ("task %p finalize", task);
169 if (priv->thr_notify)
170 priv->thr_notify (priv->thr_user_data);
171 priv->thr_notify = NULL;
172 priv->thr_user_data = NULL;
174 gst_object_unref (priv->pool);
176 /* task thread cannot be running here since it holds a ref
177 * to the task so that the finalize could not have happened */
178 g_cond_free (task->cond);
181 G_OBJECT_CLASS (gst_task_parent_class)->finalize (object);
184 /* should be called with the object LOCK */
186 gst_task_configure_name (GstTask * task)
188 #ifdef HAVE_SYS_PRCTL_H
190 gchar thread_name[17] = { 0, };
192 name = GST_OBJECT_NAME (task);
194 /* set the thread name to something easily identifiable */
195 if (!snprintf (thread_name, 17, "%s", GST_STR_NULL (name))) {
196 GST_DEBUG_OBJECT (task, "Could not create thread name for '%s'", name);
198 GST_DEBUG_OBJECT (task, "Setting thread name to '%s'", thread_name);
199 if (prctl (PR_SET_NAME, (unsigned long int) thread_name))
200 GST_DEBUG_OBJECT (task, "Failed to set thread name");
206 gst_task_func (GstTask * task)
208 GStaticRecMutex *lock;
210 GstTaskPrivate *priv;
214 tself = g_thread_self ();
216 GST_DEBUG ("Entering task %p, thread %p", task, tself);
218 /* we have to grab the lock to get the mutex. We also
219 * mark our state running so that nobody can mess with
221 GST_OBJECT_LOCK (task);
222 if (task->state == GST_TASK_STOPPED)
224 lock = GST_TASK_GET_LOCK (task);
225 if (G_UNLIKELY (lock == NULL))
227 task->abidata.ABI.thread = tself;
228 /* only update the priority when it was changed */
230 g_thread_set_priority (tself, priv->priority);
231 GST_OBJECT_UNLOCK (task);
233 /* fire the enter_thread callback when we need to */
234 if (priv->thr_callbacks.enter_thread)
235 priv->thr_callbacks.enter_thread (task, tself, priv->thr_user_data);
237 /* locking order is TASK_LOCK, LOCK */
238 g_static_rec_mutex_lock (lock);
239 GST_OBJECT_LOCK (task);
240 /* configure the thread name now */
241 gst_task_configure_name (task);
243 while (G_LIKELY (task->state != GST_TASK_STOPPED)) {
244 while (G_UNLIKELY (task->state == GST_TASK_PAUSED)) {
247 t = g_static_rec_mutex_unlock_full (lock);
249 g_warning ("wrong STREAM_LOCK count %d", t);
251 GST_TASK_SIGNAL (task);
252 GST_TASK_WAIT (task);
253 GST_OBJECT_UNLOCK (task);
254 /* locking order.. */
256 g_static_rec_mutex_lock_full (lock, t);
258 GST_OBJECT_LOCK (task);
259 if (G_UNLIKELY (task->state == GST_TASK_STOPPED))
262 GST_OBJECT_UNLOCK (task);
264 task->func (task->data);
266 GST_OBJECT_LOCK (task);
269 GST_OBJECT_UNLOCK (task);
270 g_static_rec_mutex_unlock (lock);
272 GST_OBJECT_LOCK (task);
273 task->abidata.ABI.thread = NULL;
276 if (priv->thr_callbacks.leave_thread) {
277 /* fire the leave_thread callback when we need to. We need to do this before
278 * we signal the task and with the task lock released. */
279 GST_OBJECT_UNLOCK (task);
280 priv->thr_callbacks.leave_thread (task, tself, priv->thr_user_data);
281 GST_OBJECT_LOCK (task);
283 /* restore normal priority when releasing back into the pool, we will not
284 * touch the priority when a custom callback has been installed. */
285 g_thread_set_priority (tself, G_THREAD_PRIORITY_NORMAL);
287 /* now we allow messing with the lock again by setting the running flag to
288 * FALSE. Together with the SIGNAL this is the sign for the _join() to
290 * Note that we still have not dropped the final ref on the task. We could
291 * check here if there is a pending join() going on and drop the last ref
292 * before releasing the lock as we can be sure that a ref is held by the
293 * caller of the join(). */
294 task->running = FALSE;
295 GST_TASK_SIGNAL (task);
296 GST_OBJECT_UNLOCK (task);
298 GST_DEBUG ("Exit task %p, thread %p", task, g_thread_self ());
300 gst_object_unref (task);
305 g_warning ("starting task without a lock");
311 * gst_task_cleanup_all:
313 * Wait for all tasks to be stopped. This is mainly used internally
314 * to ensure proper cleanup of internal data structures in test suites.
319 gst_task_cleanup_all (void)
323 if ((klass = g_type_class_peek (GST_TYPE_TASK))) {
324 init_klass_pool (klass);
330 * @func: The #GstTaskFunction to use
331 * @data: User data to pass to @func
333 * Create a new Task that will repeatedly call the provided @func
334 * with @data as a parameter. Typically the task will run in
337 * The function cannot be changed after the task has been created. You
338 * must create a new #GstTask to change the function.
340 * This function will not yet create and start a thread. Use gst_task_start() or
341 * gst_task_pause() to create and start the GThread.
343 * Before the task can be used, a #GStaticRecMutex must be configured using the
344 * gst_task_set_lock() function. This lock will always be acquired while
347 * Returns: A new #GstTask.
352 gst_task_create (GstTaskFunction func, gpointer data)
356 task = g_object_newv (GST_TYPE_TASK, 0, NULL);
360 GST_DEBUG ("Created task %p", task);
367 * @task: The #GstTask to use
368 * @mutex: The #GMutex to use
370 * Set the mutex used by the task. The mutex will be acquired before
371 * calling the #GstTaskFunction.
373 * This function has to be called before calling gst_task_pause() or
379 gst_task_set_lock (GstTask * task, GStaticRecMutex * mutex)
381 GST_OBJECT_LOCK (task);
382 if (G_UNLIKELY (task->running))
384 GST_TASK_GET_LOCK (task) = mutex;
385 GST_OBJECT_UNLOCK (task);
392 GST_OBJECT_UNLOCK (task);
393 g_warning ("cannot call set_lock on a running task");
398 * gst_task_set_priority:
400 * @priority: a new priority for @task
402 * Changes the priority of @task to @priority.
404 * Note: try not to depend on task priorities.
411 gst_task_set_priority (GstTask * task, GThreadPriority priority)
413 GstTaskPrivate *priv;
416 g_return_if_fail (GST_IS_TASK (task));
420 GST_OBJECT_LOCK (task);
421 priv->prio_set = TRUE;
422 priv->priority = priority;
423 thread = task->abidata.ABI.thread;
424 if (thread != NULL) {
425 /* if this task already has a thread, we can configure the priority right
426 * away, else we do that when we assign a thread to the task. */
427 g_thread_set_priority (thread, priority);
429 GST_OBJECT_UNLOCK (task);
436 * Get the #GstTaskPool that this task will use for its streaming
441 * Returns: the #GstTaskPool used by @task. gst_object_unref()
447 gst_task_get_pool (GstTask * task)
450 GstTaskPrivate *priv;
452 g_return_val_if_fail (GST_IS_TASK (task), NULL);
456 GST_OBJECT_LOCK (task);
457 result = gst_object_ref (priv->pool);
458 GST_OBJECT_UNLOCK (task);
466 * @pool: a #GstTaskPool
468 * Set @pool as the new GstTaskPool for @task. Any new streaming threads that
469 * will be created by @task will now use @pool.
476 gst_task_set_pool (GstTask * task, GstTaskPool * pool)
479 GstTaskPrivate *priv;
481 g_return_if_fail (GST_IS_TASK (task));
482 g_return_if_fail (GST_IS_TASK_POOL (pool));
486 GST_OBJECT_LOCK (task);
487 if (priv->pool != pool) {
489 priv->pool = gst_object_ref (pool);
492 GST_OBJECT_UNLOCK (task);
495 gst_object_unref (old);
500 * gst_task_set_thread_callbacks:
501 * @task: The #GstTask to use
502 * @callbacks: a #GstTaskThreadCallbacks pointer
503 * @user_data: user data passed to the callbacks
504 * @notify: called when @user_data is no longer referenced
506 * Set callbacks which will be executed when a new thread is needed, the thread
507 * function is entered and left and when the thread is joined.
509 * By default a thread for @task will be created from a default thread pool.
511 * Objects can use custom GThreads or can perform additional configuration of
512 * the threads (such as changing the thread priority) by installing callbacks.
519 gst_task_set_thread_callbacks (GstTask * task,
520 GstTaskThreadCallbacks * callbacks, gpointer user_data,
521 GDestroyNotify notify)
523 GDestroyNotify old_notify;
525 g_return_if_fail (task != NULL);
526 g_return_if_fail (GST_IS_TASK (task));
527 g_return_if_fail (callbacks != NULL);
529 GST_OBJECT_LOCK (task);
530 old_notify = task->priv->thr_notify;
535 old_data = task->priv->thr_user_data;
537 task->priv->thr_user_data = NULL;
538 task->priv->thr_notify = NULL;
539 GST_OBJECT_UNLOCK (task);
541 old_notify (old_data);
543 GST_OBJECT_LOCK (task);
545 task->priv->thr_callbacks = *callbacks;
546 task->priv->thr_user_data = user_data;
547 task->priv->thr_notify = notify;
548 GST_OBJECT_UNLOCK (task);
552 * gst_task_get_state:
553 * @task: The #GstTask to query
555 * Get the current state of the task.
557 * Returns: The #GstTaskState of the task
562 gst_task_get_state (GstTask * task)
566 g_return_val_if_fail (GST_IS_TASK (task), GST_TASK_STOPPED);
568 GST_OBJECT_LOCK (task);
569 result = task->state;
570 GST_OBJECT_UNLOCK (task);
575 /* make sure the task is running and start a thread if it's not.
576 * This function must be called with the task LOCK. */
578 start_task (GstTask * task)
581 GError *error = NULL;
582 GstTaskPrivate *priv;
586 /* new task, We ref before so that it remains alive while
587 * the thread is running. */
588 gst_object_ref (task);
589 /* mark task as running so that a join will wait until we schedule
590 * and exit the task function. */
591 task->running = TRUE;
593 /* push on the thread pool, we remember the original pool because the user
594 * could change it later on and then we join to the wrong pool. */
595 priv->pool_id = gst_object_ref (priv->pool);
597 gst_task_pool_push (priv->pool_id, (GstTaskPoolFunction) gst_task_func,
601 g_warning ("failed to create thread: %s", error->message);
602 g_error_free (error);
610 * gst_task_set_state:
612 * @state: the new task state
614 * Sets the state of @task to @state.
616 * The @task must have a lock associated with it using
617 * gst_task_set_lock() when going to GST_TASK_STARTED or GST_TASK_PAUSED or
618 * this function will return %FALSE.
622 * Returns: %TRUE if the state could be changed.
627 gst_task_set_state (GstTask * task, GstTaskState state)
632 g_return_val_if_fail (GST_IS_TASK (task), FALSE);
634 GST_DEBUG_OBJECT (task, "Changing task %p to state %d", task, state);
636 GST_OBJECT_LOCK (task);
637 if (state != GST_TASK_STOPPED)
638 if (G_UNLIKELY (GST_TASK_GET_LOCK (task) == NULL))
641 /* if the state changed, do our thing */
646 case GST_TASK_STOPPED:
647 /* If the task already has a thread scheduled we don't have to do
649 if (G_UNLIKELY (!task->running))
650 res = start_task (task);
652 case GST_TASK_PAUSED:
653 /* when we are paused, signal to go to the new state */
654 GST_TASK_SIGNAL (task);
656 case GST_TASK_STARTED:
657 /* if we were started, we'll go to the new state after the next
662 GST_OBJECT_UNLOCK (task);
669 GST_WARNING_OBJECT (task, "state %d set on task without a lock", state);
670 GST_OBJECT_UNLOCK (task);
671 g_warning ("task without a lock can't be set to state %d", state);
678 * @task: The #GstTask to start
680 * Starts @task. The @task must have a lock associated with it using
681 * gst_task_set_lock() or this function will return %FALSE.
683 * Returns: %TRUE if the task could be started.
688 gst_task_start (GstTask * task)
690 return gst_task_set_state (task, GST_TASK_STARTED);
695 * @task: The #GstTask to stop
697 * Stops @task. This method merely schedules the task to stop and
698 * will not wait for the task to have completely stopped. Use
699 * gst_task_join() to stop and wait for completion.
701 * Returns: %TRUE if the task could be stopped.
706 gst_task_stop (GstTask * task)
708 return gst_task_set_state (task, GST_TASK_STOPPED);
713 * @task: The #GstTask to pause
715 * Pauses @task. This method can also be called on a task in the
716 * stopped state, in which case a thread will be started and will remain
717 * in the paused state. This function does not wait for the task to complete
720 * Returns: %TRUE if the task could be paused.
725 gst_task_pause (GstTask * task)
727 return gst_task_set_state (task, GST_TASK_PAUSED);
732 * @task: The #GstTask to join
734 * Joins @task. After this call, it is safe to unref the task
735 * and clean up the lock set with gst_task_set_lock().
737 * The task will automatically be stopped with this call.
739 * This function cannot be called from within a task function as this
740 * would cause a deadlock. The function will detect this and print a
743 * Returns: %TRUE if the task could be joined.
748 gst_task_join (GstTask * task)
751 GstTaskPrivate *priv;
753 GstTaskPool *pool = NULL;
757 g_return_val_if_fail (GST_IS_TASK (task), FALSE);
759 tself = g_thread_self ();
761 GST_DEBUG_OBJECT (task, "Joining task %p, thread %p", task, tself);
763 /* we don't use a real thread join here because we are using
765 GST_OBJECT_LOCK (task);
766 if (G_UNLIKELY (tself == task->abidata.ABI.thread))
768 task->state = GST_TASK_STOPPED;
769 /* signal the state change for when it was blocked in PAUSED. */
770 GST_TASK_SIGNAL (task);
771 /* we set the running flag when pushing the task on the thread pool.
772 * This means that the task function might not be called when we try
773 * to join it here. */
774 while (G_LIKELY (task->running))
775 GST_TASK_WAIT (task);
776 /* clean the thread */
777 task->abidata.ABI.thread = NULL;
778 /* get the id and pool to join */
779 pool = priv->pool_id;
781 priv->pool_id = NULL;
783 GST_OBJECT_UNLOCK (task);
787 gst_task_pool_join (pool, id);
788 gst_object_unref (pool);
791 GST_DEBUG_OBJECT (task, "Joined task %p", task);
798 GST_WARNING_OBJECT (task, "trying to join task from its thread");
799 GST_OBJECT_UNLOCK (task);
800 g_warning ("\nTrying to join task %p from its thread would deadlock.\n"
801 "You cannot change the state of an element from its streaming\n"
802 "thread. Use g_idle_add() or post a GstMessage on the bus to\n"
803 "schedule the state change from the main thread.\n", task);