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;
109 struct _THREADNAME_INFO
111 DWORD dwType; // must be 0x1000
112 LPCSTR szName; // pointer to name (in user addr space)
113 DWORD dwThreadID; // thread ID (-1=caller thread)
114 DWORD dwFlags; // reserved for future use, must be zero
116 typedef struct _THREADNAME_INFO THREADNAME_INFO;
119 SetThreadName (DWORD dwThreadID, LPCSTR szThreadName)
121 THREADNAME_INFO info;
122 info.dwType = 0x1000;
123 info.szName = szThreadName;
124 info.dwThreadID = dwThreadID;
128 RaiseException (0x406D1388, 0, sizeof (info) / sizeof (DWORD),
131 __except (EXCEPTION_CONTINUE_EXECUTION) {
136 static void gst_task_finalize (GObject * object);
138 static void gst_task_func (GstTask * task);
140 static GStaticMutex pool_lock = G_STATIC_MUTEX_INIT;
144 GST_DEBUG_CATEGORY_INIT (task_debug, "task", 0, "Processing tasks"); \
147 G_DEFINE_TYPE_WITH_CODE (GstTask, gst_task, GST_TYPE_OBJECT, _do_init);
150 init_klass_pool (GstTaskClass * klass)
152 g_static_mutex_lock (&pool_lock);
154 gst_task_pool_cleanup (klass->pool);
155 gst_object_unref (klass->pool);
157 klass->pool = gst_task_pool_new ();
158 gst_task_pool_prepare (klass->pool, NULL);
159 g_static_mutex_unlock (&pool_lock);
163 gst_task_class_init (GstTaskClass * klass)
165 GObjectClass *gobject_class;
167 gobject_class = (GObjectClass *) klass;
169 g_type_class_add_private (klass, sizeof (GstTaskPrivate));
171 gobject_class->finalize = gst_task_finalize;
173 init_klass_pool (klass);
177 gst_task_init (GstTask * task)
181 klass = GST_TASK_GET_CLASS (task);
183 task->priv = GST_TASK_GET_PRIVATE (task);
184 task->running = FALSE;
185 task->abidata.ABI.thread = NULL;
187 task->cond = g_cond_new ();
188 task->state = GST_TASK_STOPPED;
189 task->priv->prio_set = FALSE;
191 /* use the default klass pool for this task, users can
192 * override this later */
193 g_static_mutex_lock (&pool_lock);
194 task->priv->pool = gst_object_ref (klass->pool);
195 g_static_mutex_unlock (&pool_lock);
199 gst_task_finalize (GObject * object)
201 GstTask *task = GST_TASK (object);
202 GstTaskPrivate *priv = task->priv;
204 GST_DEBUG ("task %p finalize", task);
206 if (priv->thr_notify)
207 priv->thr_notify (priv->thr_user_data);
208 priv->thr_notify = NULL;
209 priv->thr_user_data = NULL;
211 gst_object_unref (priv->pool);
213 /* task thread cannot be running here since it holds a ref
214 * to the task so that the finalize could not have happened */
215 g_cond_free (task->cond);
218 G_OBJECT_CLASS (gst_task_parent_class)->finalize (object);
221 /* should be called with the object LOCK */
223 gst_task_configure_name (GstTask * task)
225 #ifdef HAVE_SYS_PRCTL_H
227 gchar thread_name[17] = { 0, };
229 name = GST_OBJECT_NAME (task);
231 /* set the thread name to something easily identifiable */
232 if (!snprintf (thread_name, 17, "%s", GST_STR_NULL (name))) {
233 GST_DEBUG_OBJECT (task, "Could not create thread name for '%s'", name);
235 GST_DEBUG_OBJECT (task, "Setting thread name to '%s'", thread_name);
236 if (prctl (PR_SET_NAME, (unsigned long int) thread_name, 0, 0, 0))
237 GST_DEBUG_OBJECT (task, "Failed to set thread name");
242 name = GST_OBJECT_NAME (task);
244 /* set the thread name to something easily identifiable */
245 GST_DEBUG_OBJECT (task, "Setting thread name to '%s'", name);
246 SetThreadName (-1, name);
251 gst_task_func (GstTask * task)
253 GStaticRecMutex *lock;
255 GstTaskPrivate *priv;
259 tself = g_thread_self ();
261 GST_DEBUG ("Entering task %p, thread %p", task, tself);
263 /* we have to grab the lock to get the mutex. We also
264 * mark our state running so that nobody can mess with
266 GST_OBJECT_LOCK (task);
267 if (task->state == GST_TASK_STOPPED)
269 lock = GST_TASK_GET_LOCK (task);
270 if (G_UNLIKELY (lock == NULL))
272 task->abidata.ABI.thread = tself;
273 /* only update the priority when it was changed */
275 g_thread_set_priority (tself, priv->priority);
276 GST_OBJECT_UNLOCK (task);
278 /* fire the enter_thread callback when we need to */
279 if (priv->thr_callbacks.enter_thread)
280 priv->thr_callbacks.enter_thread (task, tself, priv->thr_user_data);
282 /* locking order is TASK_LOCK, LOCK */
283 g_static_rec_mutex_lock (lock);
284 GST_OBJECT_LOCK (task);
285 /* configure the thread name now */
286 gst_task_configure_name (task);
288 while (G_LIKELY (task->state != GST_TASK_STOPPED)) {
289 while (G_UNLIKELY (task->state == GST_TASK_PAUSED)) {
292 t = g_static_rec_mutex_unlock_full (lock);
294 g_warning ("wrong STREAM_LOCK count %d", t);
296 GST_TASK_SIGNAL (task);
297 GST_TASK_WAIT (task);
298 GST_OBJECT_UNLOCK (task);
299 /* locking order.. */
301 g_static_rec_mutex_lock_full (lock, t);
303 GST_OBJECT_LOCK (task);
304 if (G_UNLIKELY (task->state == GST_TASK_STOPPED))
307 GST_OBJECT_UNLOCK (task);
309 task->func (task->data);
311 GST_OBJECT_LOCK (task);
314 GST_OBJECT_UNLOCK (task);
315 g_static_rec_mutex_unlock (lock);
317 GST_OBJECT_LOCK (task);
318 task->abidata.ABI.thread = NULL;
321 if (priv->thr_callbacks.leave_thread) {
322 /* fire the leave_thread callback when we need to. We need to do this before
323 * we signal the task and with the task lock released. */
324 GST_OBJECT_UNLOCK (task);
325 priv->thr_callbacks.leave_thread (task, tself, priv->thr_user_data);
326 GST_OBJECT_LOCK (task);
328 /* restore normal priority when releasing back into the pool, we will not
329 * touch the priority when a custom callback has been installed. */
330 g_thread_set_priority (tself, G_THREAD_PRIORITY_NORMAL);
332 /* now we allow messing with the lock again by setting the running flag to
333 * FALSE. Together with the SIGNAL this is the sign for the _join() to
335 * Note that we still have not dropped the final ref on the task. We could
336 * check here if there is a pending join() going on and drop the last ref
337 * before releasing the lock as we can be sure that a ref is held by the
338 * caller of the join(). */
339 task->running = FALSE;
340 GST_TASK_SIGNAL (task);
341 GST_OBJECT_UNLOCK (task);
343 GST_DEBUG ("Exit task %p, thread %p", task, g_thread_self ());
345 gst_object_unref (task);
350 g_warning ("starting task without a lock");
356 * gst_task_cleanup_all:
358 * Wait for all tasks to be stopped. This is mainly used internally
359 * to ensure proper cleanup of internal data structures in test suites.
364 gst_task_cleanup_all (void)
368 if ((klass = g_type_class_peek (GST_TYPE_TASK))) {
369 init_klass_pool (klass);
375 * @func: The #GstTaskFunction to use
376 * @data: User data to pass to @func
378 * Create a new Task that will repeatedly call the provided @func
379 * with @data as a parameter. Typically the task will run in
382 * The function cannot be changed after the task has been created. You
383 * must create a new #GstTask to change the function.
385 * This function will not yet create and start a thread. Use gst_task_start() or
386 * gst_task_pause() to create and start the GThread.
388 * Before the task can be used, a #GStaticRecMutex must be configured using the
389 * gst_task_set_lock() function. This lock will always be acquired while
392 * Returns: A new #GstTask.
397 gst_task_create (GstTaskFunction func, gpointer data)
401 task = g_object_newv (GST_TYPE_TASK, 0, NULL);
405 GST_DEBUG ("Created task %p", task);
412 * @task: The #GstTask to use
413 * @mutex: The #GMutex to use
415 * Set the mutex used by the task. The mutex will be acquired before
416 * calling the #GstTaskFunction.
418 * This function has to be called before calling gst_task_pause() or
424 gst_task_set_lock (GstTask * task, GStaticRecMutex * mutex)
426 GST_OBJECT_LOCK (task);
427 if (G_UNLIKELY (task->running))
429 GST_TASK_GET_LOCK (task) = mutex;
430 GST_OBJECT_UNLOCK (task);
437 GST_OBJECT_UNLOCK (task);
438 g_warning ("cannot call set_lock on a running task");
443 * gst_task_set_priority:
445 * @priority: a new priority for @task
447 * Changes the priority of @task to @priority.
449 * Note: try not to depend on task priorities.
456 gst_task_set_priority (GstTask * task, GThreadPriority priority)
458 GstTaskPrivate *priv;
461 g_return_if_fail (GST_IS_TASK (task));
465 GST_OBJECT_LOCK (task);
466 priv->prio_set = TRUE;
467 priv->priority = priority;
468 thread = task->abidata.ABI.thread;
469 if (thread != NULL) {
470 /* if this task already has a thread, we can configure the priority right
471 * away, else we do that when we assign a thread to the task. */
472 g_thread_set_priority (thread, priority);
474 GST_OBJECT_UNLOCK (task);
481 * Get the #GstTaskPool that this task will use for its streaming
486 * Returns: the #GstTaskPool used by @task. gst_object_unref()
492 gst_task_get_pool (GstTask * task)
495 GstTaskPrivate *priv;
497 g_return_val_if_fail (GST_IS_TASK (task), NULL);
501 GST_OBJECT_LOCK (task);
502 result = gst_object_ref (priv->pool);
503 GST_OBJECT_UNLOCK (task);
511 * @pool: a #GstTaskPool
513 * Set @pool as the new GstTaskPool for @task. Any new streaming threads that
514 * will be created by @task will now use @pool.
521 gst_task_set_pool (GstTask * task, GstTaskPool * pool)
524 GstTaskPrivate *priv;
526 g_return_if_fail (GST_IS_TASK (task));
527 g_return_if_fail (GST_IS_TASK_POOL (pool));
531 GST_OBJECT_LOCK (task);
532 if (priv->pool != pool) {
534 priv->pool = gst_object_ref (pool);
537 GST_OBJECT_UNLOCK (task);
540 gst_object_unref (old);
545 * gst_task_set_thread_callbacks:
546 * @task: The #GstTask to use
547 * @callbacks: a #GstTaskThreadCallbacks pointer
548 * @user_data: user data passed to the callbacks
549 * @notify: called when @user_data is no longer referenced
551 * Set callbacks which will be executed when a new thread is needed, the thread
552 * function is entered and left and when the thread is joined.
554 * By default a thread for @task will be created from a default thread pool.
556 * Objects can use custom GThreads or can perform additional configuration of
557 * the threads (such as changing the thread priority) by installing callbacks.
564 gst_task_set_thread_callbacks (GstTask * task,
565 GstTaskThreadCallbacks * callbacks, gpointer user_data,
566 GDestroyNotify notify)
568 GDestroyNotify old_notify;
570 g_return_if_fail (task != NULL);
571 g_return_if_fail (GST_IS_TASK (task));
572 g_return_if_fail (callbacks != NULL);
574 GST_OBJECT_LOCK (task);
575 old_notify = task->priv->thr_notify;
580 old_data = task->priv->thr_user_data;
582 task->priv->thr_user_data = NULL;
583 task->priv->thr_notify = NULL;
584 GST_OBJECT_UNLOCK (task);
586 old_notify (old_data);
588 GST_OBJECT_LOCK (task);
590 task->priv->thr_callbacks = *callbacks;
591 task->priv->thr_user_data = user_data;
592 task->priv->thr_notify = notify;
593 GST_OBJECT_UNLOCK (task);
597 * gst_task_get_state:
598 * @task: The #GstTask to query
600 * Get the current state of the task.
602 * Returns: The #GstTaskState of the task
607 gst_task_get_state (GstTask * task)
611 g_return_val_if_fail (GST_IS_TASK (task), GST_TASK_STOPPED);
613 GST_OBJECT_LOCK (task);
614 result = task->state;
615 GST_OBJECT_UNLOCK (task);
620 /* make sure the task is running and start a thread if it's not.
621 * This function must be called with the task LOCK. */
623 start_task (GstTask * task)
626 GError *error = NULL;
627 GstTaskPrivate *priv;
631 /* new task, We ref before so that it remains alive while
632 * the thread is running. */
633 gst_object_ref (task);
634 /* mark task as running so that a join will wait until we schedule
635 * and exit the task function. */
636 task->running = TRUE;
638 /* push on the thread pool, we remember the original pool because the user
639 * could change it later on and then we join to the wrong pool. */
640 priv->pool_id = gst_object_ref (priv->pool);
642 gst_task_pool_push (priv->pool_id, (GstTaskPoolFunction) gst_task_func,
646 g_warning ("failed to create thread: %s", error->message);
647 g_error_free (error);
655 * gst_task_set_state:
657 * @state: the new task state
659 * Sets the state of @task to @state.
661 * The @task must have a lock associated with it using
662 * gst_task_set_lock() when going to GST_TASK_STARTED or GST_TASK_PAUSED or
663 * this function will return %FALSE.
667 * Returns: %TRUE if the state could be changed.
672 gst_task_set_state (GstTask * task, GstTaskState state)
677 g_return_val_if_fail (GST_IS_TASK (task), FALSE);
679 GST_DEBUG_OBJECT (task, "Changing task %p to state %d", task, state);
681 GST_OBJECT_LOCK (task);
682 if (state != GST_TASK_STOPPED)
683 if (G_UNLIKELY (GST_TASK_GET_LOCK (task) == NULL))
686 /* if the state changed, do our thing */
691 case GST_TASK_STOPPED:
692 /* If the task already has a thread scheduled we don't have to do
694 if (G_UNLIKELY (!task->running))
695 res = start_task (task);
697 case GST_TASK_PAUSED:
698 /* when we are paused, signal to go to the new state */
699 GST_TASK_SIGNAL (task);
701 case GST_TASK_STARTED:
702 /* if we were started, we'll go to the new state after the next
707 GST_OBJECT_UNLOCK (task);
714 GST_WARNING_OBJECT (task, "state %d set on task without a lock", state);
715 GST_OBJECT_UNLOCK (task);
716 g_warning ("task without a lock can't be set to state %d", state);
723 * @task: The #GstTask to start
725 * Starts @task. The @task must have a lock associated with it using
726 * gst_task_set_lock() or this function will return %FALSE.
728 * Returns: %TRUE if the task could be started.
733 gst_task_start (GstTask * task)
735 return gst_task_set_state (task, GST_TASK_STARTED);
740 * @task: The #GstTask to stop
742 * Stops @task. This method merely schedules the task to stop and
743 * will not wait for the task to have completely stopped. Use
744 * gst_task_join() to stop and wait for completion.
746 * Returns: %TRUE if the task could be stopped.
751 gst_task_stop (GstTask * task)
753 return gst_task_set_state (task, GST_TASK_STOPPED);
758 * @task: The #GstTask to pause
760 * Pauses @task. This method can also be called on a task in the
761 * stopped state, in which case a thread will be started and will remain
762 * in the paused state. This function does not wait for the task to complete
765 * Returns: %TRUE if the task could be paused.
770 gst_task_pause (GstTask * task)
772 return gst_task_set_state (task, GST_TASK_PAUSED);
777 * @task: The #GstTask to join
779 * Joins @task. After this call, it is safe to unref the task
780 * and clean up the lock set with gst_task_set_lock().
782 * The task will automatically be stopped with this call.
784 * This function cannot be called from within a task function as this
785 * would cause a deadlock. The function will detect this and print a
788 * Returns: %TRUE if the task could be joined.
793 gst_task_join (GstTask * task)
796 GstTaskPrivate *priv;
798 GstTaskPool *pool = NULL;
802 g_return_val_if_fail (GST_IS_TASK (task), FALSE);
804 tself = g_thread_self ();
806 GST_DEBUG_OBJECT (task, "Joining task %p, thread %p", task, tself);
808 /* we don't use a real thread join here because we are using
810 GST_OBJECT_LOCK (task);
811 if (G_UNLIKELY (tself == task->abidata.ABI.thread))
813 task->state = GST_TASK_STOPPED;
814 /* signal the state change for when it was blocked in PAUSED. */
815 GST_TASK_SIGNAL (task);
816 /* we set the running flag when pushing the task on the thread pool.
817 * This means that the task function might not be called when we try
818 * to join it here. */
819 while (G_LIKELY (task->running))
820 GST_TASK_WAIT (task);
821 /* clean the thread */
822 task->abidata.ABI.thread = NULL;
823 /* get the id and pool to join */
824 pool = priv->pool_id;
826 priv->pool_id = NULL;
828 GST_OBJECT_UNLOCK (task);
832 gst_task_pool_join (pool, id);
833 gst_object_unref (pool);
836 GST_DEBUG_OBJECT (task, "Joined task %p", task);
843 GST_WARNING_OBJECT (task, "trying to join task from its thread");
844 GST_OBJECT_UNLOCK (task);
845 g_warning ("\nTrying to join task %p from its thread would deadlock.\n"
846 "You cannot change the state of an element from its streaming\n"
847 "thread. Use g_idle_add() or post a GstMessage on the bus to\n"
848 "schedule the state change from the main thread.\n", task);