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 SET_TASK_STATE(t,s) (g_atomic_int_set (&GST_TASK_STATE(t), (s)))
86 #define GET_TASK_STATE(t) (g_atomic_int_get (&GST_TASK_STATE(t)))
88 #define GST_TASK_GET_PRIVATE(obj) \
89 (G_TYPE_INSTANCE_GET_PRIVATE ((obj), GST_TYPE_TASK, GstTaskPrivate))
91 struct _GstTaskPrivate
93 /* callbacks for managing the thread of this task */
94 GstTaskThreadCallbacks thr_callbacks;
95 gpointer thr_user_data;
96 GDestroyNotify thr_notify;
99 GThreadPriority priority;
101 /* configured pool */
104 /* remember the pool and id that is currently running. */
106 GstTaskPool *pool_id;
112 struct _THREADNAME_INFO
114 DWORD dwType; // must be 0x1000
115 LPCSTR szName; // pointer to name (in user addr space)
116 DWORD dwThreadID; // thread ID (-1=caller thread)
117 DWORD dwFlags; // reserved for future use, must be zero
119 typedef struct _THREADNAME_INFO THREADNAME_INFO;
122 SetThreadName (DWORD dwThreadID, LPCSTR szThreadName)
124 THREADNAME_INFO info;
125 info.dwType = 0x1000;
126 info.szName = szThreadName;
127 info.dwThreadID = dwThreadID;
131 RaiseException (0x406D1388, 0, sizeof (info) / sizeof (DWORD),
134 __except (EXCEPTION_CONTINUE_EXECUTION) {
139 static void gst_task_finalize (GObject * object);
141 static void gst_task_func (GstTask * task);
143 static GStaticMutex pool_lock = G_STATIC_MUTEX_INIT;
147 GST_DEBUG_CATEGORY_INIT (task_debug, "task", 0, "Processing tasks"); \
150 G_DEFINE_TYPE_WITH_CODE (GstTask, gst_task, GST_TYPE_OBJECT, _do_init);
153 init_klass_pool (GstTaskClass * klass)
155 g_static_mutex_lock (&pool_lock);
157 gst_task_pool_cleanup (klass->pool);
158 gst_object_unref (klass->pool);
160 klass->pool = gst_task_pool_new ();
161 gst_task_pool_prepare (klass->pool, NULL);
162 g_static_mutex_unlock (&pool_lock);
166 gst_task_class_init (GstTaskClass * klass)
168 GObjectClass *gobject_class;
170 gobject_class = (GObjectClass *) klass;
172 g_type_class_add_private (klass, sizeof (GstTaskPrivate));
174 gobject_class->finalize = gst_task_finalize;
176 init_klass_pool (klass);
180 gst_task_init (GstTask * task)
184 klass = GST_TASK_GET_CLASS (task);
186 task->priv = GST_TASK_GET_PRIVATE (task);
187 task->running = FALSE;
188 task->abidata.ABI.thread = NULL;
190 task->cond = g_cond_new ();
191 SET_TASK_STATE (task, GST_TASK_STOPPED);
192 task->priv->prio_set = FALSE;
194 /* use the default klass pool for this task, users can
195 * override this later */
196 g_static_mutex_lock (&pool_lock);
197 task->priv->pool = gst_object_ref (klass->pool);
198 g_static_mutex_unlock (&pool_lock);
202 gst_task_finalize (GObject * object)
204 GstTask *task = GST_TASK (object);
205 GstTaskPrivate *priv = task->priv;
207 GST_DEBUG ("task %p finalize", task);
209 if (priv->thr_notify)
210 priv->thr_notify (priv->thr_user_data);
211 priv->thr_notify = NULL;
212 priv->thr_user_data = NULL;
214 gst_object_unref (priv->pool);
216 /* task thread cannot be running here since it holds a ref
217 * to the task so that the finalize could not have happened */
218 g_cond_free (task->cond);
221 G_OBJECT_CLASS (gst_task_parent_class)->finalize (object);
224 /* should be called with the object LOCK */
226 gst_task_configure_name (GstTask * task)
228 #ifdef HAVE_SYS_PRCTL_H
230 gchar thread_name[17] = { 0, };
232 GST_OBJECT_LOCK (task);
233 name = GST_OBJECT_NAME (task);
235 /* set the thread name to something easily identifiable */
236 if (!snprintf (thread_name, 17, "%s", GST_STR_NULL (name))) {
237 GST_DEBUG_OBJECT (task, "Could not create thread name for '%s'", name);
239 GST_DEBUG_OBJECT (task, "Setting thread name to '%s'", thread_name);
240 if (prctl (PR_SET_NAME, (unsigned long int) thread_name, 0, 0, 0))
241 GST_DEBUG_OBJECT (task, "Failed to set thread name");
243 GST_OBJECT_UNLOCK (task);
247 name = GST_OBJECT_NAME (task);
249 /* set the thread name to something easily identifiable */
250 GST_DEBUG_OBJECT (task, "Setting thread name to '%s'", name);
251 SetThreadName (-1, name);
256 gst_task_func (GstTask * task)
258 GStaticRecMutex *lock;
260 GstTaskPrivate *priv;
264 tself = g_thread_self ();
266 GST_DEBUG ("Entering task %p, thread %p", task, tself);
268 /* we have to grab the lock to get the mutex. We also
269 * mark our state running so that nobody can mess with
271 GST_OBJECT_LOCK (task);
272 if (GET_TASK_STATE (task) == GST_TASK_STOPPED)
274 lock = GST_TASK_GET_LOCK (task);
275 if (G_UNLIKELY (lock == NULL))
277 task->abidata.ABI.thread = tself;
278 /* only update the priority when it was changed */
280 g_thread_set_priority (tself, priv->priority);
281 GST_OBJECT_UNLOCK (task);
283 /* fire the enter_thread callback when we need to */
284 if (priv->thr_callbacks.enter_thread)
285 priv->thr_callbacks.enter_thread (task, tself, priv->thr_user_data);
287 /* locking order is TASK_LOCK, LOCK */
288 g_static_rec_mutex_lock (lock);
289 /* configure the thread name now */
290 gst_task_configure_name (task);
292 while (G_LIKELY (GET_TASK_STATE (task) != GST_TASK_STOPPED)) {
293 if (G_UNLIKELY (GET_TASK_STATE (task) == GST_TASK_PAUSED)) {
294 GST_OBJECT_LOCK (task);
295 while (G_UNLIKELY (GST_TASK_STATE (task) == GST_TASK_PAUSED)) {
298 t = g_static_rec_mutex_unlock_full (lock);
300 g_warning ("wrong STREAM_LOCK count %d", t);
302 GST_TASK_SIGNAL (task);
303 GST_TASK_WAIT (task);
304 GST_OBJECT_UNLOCK (task);
305 /* locking order.. */
307 g_static_rec_mutex_lock_full (lock, t);
309 GST_OBJECT_LOCK (task);
310 if (G_UNLIKELY (GET_TASK_STATE (task) == GST_TASK_STOPPED)) {
311 GST_OBJECT_UNLOCK (task);
315 GST_OBJECT_UNLOCK (task);
318 task->func (task->data);
321 g_static_rec_mutex_unlock (lock);
323 GST_OBJECT_LOCK (task);
324 task->abidata.ABI.thread = NULL;
327 if (priv->thr_callbacks.leave_thread) {
328 /* fire the leave_thread callback when we need to. We need to do this before
329 * we signal the task and with the task lock released. */
330 GST_OBJECT_UNLOCK (task);
331 priv->thr_callbacks.leave_thread (task, tself, priv->thr_user_data);
332 GST_OBJECT_LOCK (task);
334 /* restore normal priority when releasing back into the pool, we will not
335 * touch the priority when a custom callback has been installed. */
336 g_thread_set_priority (tself, G_THREAD_PRIORITY_NORMAL);
338 /* now we allow messing with the lock again by setting the running flag to
339 * FALSE. Together with the SIGNAL this is the sign for the _join() to
341 * Note that we still have not dropped the final ref on the task. We could
342 * check here if there is a pending join() going on and drop the last ref
343 * before releasing the lock as we can be sure that a ref is held by the
344 * caller of the join(). */
345 task->running = FALSE;
346 GST_TASK_SIGNAL (task);
347 GST_OBJECT_UNLOCK (task);
349 GST_DEBUG ("Exit task %p, thread %p", task, g_thread_self ());
351 gst_object_unref (task);
356 g_warning ("starting task without a lock");
362 * gst_task_cleanup_all:
364 * Wait for all tasks to be stopped. This is mainly used internally
365 * to ensure proper cleanup of internal data structures in test suites.
370 gst_task_cleanup_all (void)
374 if ((klass = g_type_class_peek (GST_TYPE_TASK))) {
375 init_klass_pool (klass);
381 * @func: The #GstTaskFunction to use
382 * @data: User data to pass to @func
384 * Create a new Task that will repeatedly call the provided @func
385 * with @data as a parameter. Typically the task will run in
388 * The function cannot be changed after the task has been created. You
389 * must create a new #GstTask to change the function.
391 * This function will not yet create and start a thread. Use gst_task_start() or
392 * gst_task_pause() to create and start the GThread.
394 * Before the task can be used, a #GStaticRecMutex must be configured using the
395 * gst_task_set_lock() function. This lock will always be acquired while
398 * Returns: A new #GstTask.
403 gst_task_create (GstTaskFunction func, gpointer data)
407 task = g_object_newv (GST_TYPE_TASK, 0, NULL);
411 GST_DEBUG ("Created task %p", task);
418 * @task: The #GstTask to use
419 * @mutex: The #GMutex to use
421 * Set the mutex used by the task. The mutex will be acquired before
422 * calling the #GstTaskFunction.
424 * This function has to be called before calling gst_task_pause() or
430 gst_task_set_lock (GstTask * task, GStaticRecMutex * mutex)
432 GST_OBJECT_LOCK (task);
433 if (G_UNLIKELY (task->running))
435 GST_TASK_GET_LOCK (task) = mutex;
436 GST_OBJECT_UNLOCK (task);
443 GST_OBJECT_UNLOCK (task);
444 g_warning ("cannot call set_lock on a running task");
449 * gst_task_set_priority:
451 * @priority: a new priority for @task
453 * Changes the priority of @task to @priority.
455 * Note: try not to depend on task priorities.
462 gst_task_set_priority (GstTask * task, GThreadPriority priority)
464 GstTaskPrivate *priv;
467 g_return_if_fail (GST_IS_TASK (task));
471 GST_OBJECT_LOCK (task);
472 priv->prio_set = TRUE;
473 priv->priority = priority;
474 thread = task->abidata.ABI.thread;
475 if (thread != NULL) {
476 /* if this task already has a thread, we can configure the priority right
477 * away, else we do that when we assign a thread to the task. */
478 g_thread_set_priority (thread, priority);
480 GST_OBJECT_UNLOCK (task);
487 * Get the #GstTaskPool that this task will use for its streaming
492 * Returns: the #GstTaskPool used by @task. gst_object_unref()
498 gst_task_get_pool (GstTask * task)
501 GstTaskPrivate *priv;
503 g_return_val_if_fail (GST_IS_TASK (task), NULL);
507 GST_OBJECT_LOCK (task);
508 result = gst_object_ref (priv->pool);
509 GST_OBJECT_UNLOCK (task);
517 * @pool: a #GstTaskPool
519 * Set @pool as the new GstTaskPool for @task. Any new streaming threads that
520 * will be created by @task will now use @pool.
527 gst_task_set_pool (GstTask * task, GstTaskPool * pool)
530 GstTaskPrivate *priv;
532 g_return_if_fail (GST_IS_TASK (task));
533 g_return_if_fail (GST_IS_TASK_POOL (pool));
537 GST_OBJECT_LOCK (task);
538 if (priv->pool != pool) {
540 priv->pool = gst_object_ref (pool);
543 GST_OBJECT_UNLOCK (task);
546 gst_object_unref (old);
551 * gst_task_set_thread_callbacks:
552 * @task: The #GstTask to use
553 * @callbacks: a #GstTaskThreadCallbacks pointer
554 * @user_data: user data passed to the callbacks
555 * @notify: called when @user_data is no longer referenced
557 * Set callbacks which will be executed when a new thread is needed, the thread
558 * function is entered and left and when the thread is joined.
560 * By default a thread for @task will be created from a default thread pool.
562 * Objects can use custom GThreads or can perform additional configuration of
563 * the threads (such as changing the thread priority) by installing callbacks.
570 gst_task_set_thread_callbacks (GstTask * task,
571 GstTaskThreadCallbacks * callbacks, gpointer user_data,
572 GDestroyNotify notify)
574 GDestroyNotify old_notify;
576 g_return_if_fail (task != NULL);
577 g_return_if_fail (GST_IS_TASK (task));
578 g_return_if_fail (callbacks != NULL);
580 GST_OBJECT_LOCK (task);
581 old_notify = task->priv->thr_notify;
586 old_data = task->priv->thr_user_data;
588 task->priv->thr_user_data = NULL;
589 task->priv->thr_notify = NULL;
590 GST_OBJECT_UNLOCK (task);
592 old_notify (old_data);
594 GST_OBJECT_LOCK (task);
596 task->priv->thr_callbacks = *callbacks;
597 task->priv->thr_user_data = user_data;
598 task->priv->thr_notify = notify;
599 GST_OBJECT_UNLOCK (task);
603 * gst_task_get_state:
604 * @task: The #GstTask to query
606 * Get the current state of the task.
608 * Returns: The #GstTaskState of the task
613 gst_task_get_state (GstTask * task)
617 g_return_val_if_fail (GST_IS_TASK (task), GST_TASK_STOPPED);
619 result = GET_TASK_STATE (task);
624 /* make sure the task is running and start a thread if it's not.
625 * This function must be called with the task LOCK. */
627 start_task (GstTask * task)
630 GError *error = NULL;
631 GstTaskPrivate *priv;
635 /* new task, We ref before so that it remains alive while
636 * the thread is running. */
637 gst_object_ref (task);
638 /* mark task as running so that a join will wait until we schedule
639 * and exit the task function. */
640 task->running = TRUE;
642 /* push on the thread pool, we remember the original pool because the user
643 * could change it later on and then we join to the wrong pool. */
644 priv->pool_id = gst_object_ref (priv->pool);
646 gst_task_pool_push (priv->pool_id, (GstTaskPoolFunction) gst_task_func,
650 g_warning ("failed to create thread: %s", error->message);
651 g_error_free (error);
659 * gst_task_set_state:
661 * @state: the new task state
663 * Sets the state of @task to @state.
665 * The @task must have a lock associated with it using
666 * gst_task_set_lock() when going to GST_TASK_STARTED or GST_TASK_PAUSED or
667 * this function will return %FALSE.
671 * Returns: %TRUE if the state could be changed.
676 gst_task_set_state (GstTask * task, GstTaskState state)
681 g_return_val_if_fail (GST_IS_TASK (task), FALSE);
683 GST_DEBUG_OBJECT (task, "Changing task %p to state %d", task, state);
685 GST_OBJECT_LOCK (task);
686 if (state != GST_TASK_STOPPED)
687 if (G_UNLIKELY (GST_TASK_GET_LOCK (task) == NULL))
690 /* if the state changed, do our thing */
691 old = GET_TASK_STATE (task);
693 SET_TASK_STATE (task, state);
695 case GST_TASK_STOPPED:
696 /* If the task already has a thread scheduled we don't have to do
698 if (G_UNLIKELY (!task->running))
699 res = start_task (task);
701 case GST_TASK_PAUSED:
702 /* when we are paused, signal to go to the new state */
703 GST_TASK_SIGNAL (task);
705 case GST_TASK_STARTED:
706 /* if we were started, we'll go to the new state after the next
711 GST_OBJECT_UNLOCK (task);
718 GST_WARNING_OBJECT (task, "state %d set on task without a lock", state);
719 GST_OBJECT_UNLOCK (task);
720 g_warning ("task without a lock can't be set to state %d", state);
727 * @task: The #GstTask to start
729 * Starts @task. The @task must have a lock associated with it using
730 * gst_task_set_lock() or this function will return %FALSE.
732 * Returns: %TRUE if the task could be started.
737 gst_task_start (GstTask * task)
739 return gst_task_set_state (task, GST_TASK_STARTED);
744 * @task: The #GstTask to stop
746 * Stops @task. This method merely schedules the task to stop and
747 * will not wait for the task to have completely stopped. Use
748 * gst_task_join() to stop and wait for completion.
750 * Returns: %TRUE if the task could be stopped.
755 gst_task_stop (GstTask * task)
757 return gst_task_set_state (task, GST_TASK_STOPPED);
762 * @task: The #GstTask to pause
764 * Pauses @task. This method can also be called on a task in the
765 * stopped state, in which case a thread will be started and will remain
766 * in the paused state. This function does not wait for the task to complete
769 * Returns: %TRUE if the task could be paused.
774 gst_task_pause (GstTask * task)
776 return gst_task_set_state (task, GST_TASK_PAUSED);
781 * @task: The #GstTask to join
783 * Joins @task. After this call, it is safe to unref the task
784 * and clean up the lock set with gst_task_set_lock().
786 * The task will automatically be stopped with this call.
788 * This function cannot be called from within a task function as this
789 * would cause a deadlock. The function will detect this and print a
792 * Returns: %TRUE if the task could be joined.
797 gst_task_join (GstTask * task)
800 GstTaskPrivate *priv;
802 GstTaskPool *pool = NULL;
806 g_return_val_if_fail (GST_IS_TASK (task), FALSE);
808 tself = g_thread_self ();
810 GST_DEBUG_OBJECT (task, "Joining task %p, thread %p", task, tself);
812 /* we don't use a real thread join here because we are using
814 GST_OBJECT_LOCK (task);
815 if (G_UNLIKELY (tself == task->abidata.ABI.thread))
817 SET_TASK_STATE (task, GST_TASK_STOPPED);
818 /* signal the state change for when it was blocked in PAUSED. */
819 GST_TASK_SIGNAL (task);
820 /* we set the running flag when pushing the task on the thread pool.
821 * This means that the task function might not be called when we try
822 * to join it here. */
823 while (G_LIKELY (task->running))
824 GST_TASK_WAIT (task);
825 /* clean the thread */
826 task->abidata.ABI.thread = NULL;
827 /* get the id and pool to join */
828 pool = priv->pool_id;
830 priv->pool_id = NULL;
832 GST_OBJECT_UNLOCK (task);
836 gst_task_pool_join (pool, id);
837 gst_object_unref (pool);
840 GST_DEBUG_OBJECT (task, "Joined task %p", task);
847 GST_WARNING_OBJECT (task, "trying to join task from its thread");
848 GST_OBJECT_UNLOCK (task);
849 g_warning ("\nTrying to join task %p from its thread would deadlock.\n"
850 "You cannot change the state of an element from its streaming\n"
851 "thread. Use g_idle_add() or post a GstMessage on the bus to\n"
852 "schedule the state change from the main thread.\n", task);