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"
75 #include "glib-compat-private.h"
79 #ifdef HAVE_SYS_PRCTL_H
80 #include <sys/prctl.h>
83 GST_DEBUG_CATEGORY_STATIC (task_debug);
84 #define GST_CAT_DEFAULT (task_debug)
86 #define SET_TASK_STATE(t,s) (g_atomic_int_set (&GST_TASK_STATE(t), (s)))
87 #define GET_TASK_STATE(t) ((GstTaskState) g_atomic_int_get (&GST_TASK_STATE(t)))
89 #define GST_TASK_GET_PRIVATE(obj) \
90 (G_TYPE_INSTANCE_GET_PRIVATE ((obj), GST_TYPE_TASK, GstTaskPrivate))
92 struct _GstTaskPrivate
94 /* callbacks for managing the thread of this task */
95 GstTaskThreadCallbacks thr_callbacks;
96 gpointer thr_user_data;
97 GDestroyNotify thr_notify;
100 GThreadPriority priority;
102 /* configured pool */
105 /* remember the pool and id that is currently running. */
107 GstTaskPool *pool_id;
113 struct _THREADNAME_INFO
115 DWORD dwType; // must be 0x1000
116 LPCSTR szName; // pointer to name (in user addr space)
117 DWORD dwThreadID; // thread ID (-1=caller thread)
118 DWORD dwFlags; // reserved for future use, must be zero
120 typedef struct _THREADNAME_INFO THREADNAME_INFO;
123 SetThreadName (DWORD dwThreadID, LPCSTR szThreadName)
125 THREADNAME_INFO info;
126 info.dwType = 0x1000;
127 info.szName = szThreadName;
128 info.dwThreadID = dwThreadID;
132 RaiseException (0x406D1388, 0, sizeof (info) / sizeof (DWORD),
135 __except (EXCEPTION_CONTINUE_EXECUTION) {
140 static void gst_task_finalize (GObject * object);
142 static void gst_task_func (GstTask * task);
144 static GStaticMutex pool_lock = G_STATIC_MUTEX_INIT;
148 GST_DEBUG_CATEGORY_INIT (task_debug, "task", 0, "Processing tasks"); \
151 G_DEFINE_TYPE_WITH_CODE (GstTask, gst_task, GST_TYPE_OBJECT, _do_init);
154 init_klass_pool (GstTaskClass * klass)
156 g_static_mutex_lock (&pool_lock);
158 gst_task_pool_cleanup (klass->pool);
159 gst_object_unref (klass->pool);
161 klass->pool = gst_task_pool_new ();
162 gst_task_pool_prepare (klass->pool, NULL);
163 g_static_mutex_unlock (&pool_lock);
167 gst_task_class_init (GstTaskClass * klass)
169 GObjectClass *gobject_class;
171 gobject_class = (GObjectClass *) klass;
173 g_type_class_add_private (klass, sizeof (GstTaskPrivate));
175 gobject_class->finalize = gst_task_finalize;
177 init_klass_pool (klass);
181 gst_task_init (GstTask * task)
185 klass = GST_TASK_GET_CLASS (task);
187 task->priv = GST_TASK_GET_PRIVATE (task);
188 task->running = FALSE;
189 task->abidata.ABI.thread = NULL;
191 task->cond = g_cond_new ();
192 SET_TASK_STATE (task, GST_TASK_STOPPED);
193 task->priv->prio_set = FALSE;
195 /* use the default klass pool for this task, users can
196 * override this later */
197 g_static_mutex_lock (&pool_lock);
198 task->priv->pool = gst_object_ref (klass->pool);
199 g_static_mutex_unlock (&pool_lock);
203 gst_task_finalize (GObject * object)
205 GstTask *task = GST_TASK (object);
206 GstTaskPrivate *priv = task->priv;
208 GST_DEBUG ("task %p finalize", task);
210 if (priv->thr_notify)
211 priv->thr_notify (priv->thr_user_data);
212 priv->thr_notify = NULL;
213 priv->thr_user_data = NULL;
215 gst_object_unref (priv->pool);
217 /* task thread cannot be running here since it holds a ref
218 * to the task so that the finalize could not have happened */
219 g_cond_free (task->cond);
222 G_OBJECT_CLASS (gst_task_parent_class)->finalize (object);
225 /* should be called with the object LOCK */
227 gst_task_configure_name (GstTask * task)
229 #if defined(HAVE_SYS_PRCTL_H) && defined(PR_SET_NAME)
231 gchar thread_name[17] = { 0, };
233 GST_OBJECT_LOCK (task);
234 name = GST_OBJECT_NAME (task);
236 /* set the thread name to something easily identifiable */
237 if (!snprintf (thread_name, 17, "%s", GST_STR_NULL (name))) {
238 GST_DEBUG_OBJECT (task, "Could not create thread name for '%s'", name);
240 GST_DEBUG_OBJECT (task, "Setting thread name to '%s'", thread_name);
241 if (prctl (PR_SET_NAME, (unsigned long int) thread_name, 0, 0, 0))
242 GST_DEBUG_OBJECT (task, "Failed to set thread name");
244 GST_OBJECT_UNLOCK (task);
248 name = GST_OBJECT_NAME (task);
250 /* set the thread name to something easily identifiable */
251 GST_DEBUG_OBJECT (task, "Setting thread name to '%s'", name);
252 SetThreadName (-1, name);
257 gst_task_func (GstTask * task)
259 GStaticRecMutex *lock;
261 GstTaskPrivate *priv;
265 tself = g_thread_self ();
267 GST_DEBUG ("Entering task %p, thread %p", task, tself);
269 /* we have to grab the lock to get the mutex. We also
270 * mark our state running so that nobody can mess with
272 GST_OBJECT_LOCK (task);
273 if (GET_TASK_STATE (task) == GST_TASK_STOPPED)
275 lock = GST_TASK_GET_LOCK (task);
276 if (G_UNLIKELY (lock == NULL))
278 task->abidata.ABI.thread = tself;
279 /* only update the priority when it was changed */
280 if (priv->prio_set) {
281 #if !GLIB_CHECK_VERSION (2, 31, 0)
282 g_thread_set_priority (tself, priv->priority);
284 GST_INFO_OBJECT (task, "Thread priorities no longer have any effect");
287 GST_OBJECT_UNLOCK (task);
289 /* fire the enter_thread callback when we need to */
290 if (priv->thr_callbacks.enter_thread)
291 priv->thr_callbacks.enter_thread (task, tself, priv->thr_user_data);
293 /* locking order is TASK_LOCK, LOCK */
294 g_static_rec_mutex_lock (lock);
295 /* configure the thread name now */
296 gst_task_configure_name (task);
298 while (G_LIKELY (GET_TASK_STATE (task) != GST_TASK_STOPPED)) {
299 if (G_UNLIKELY (GET_TASK_STATE (task) == GST_TASK_PAUSED)) {
300 GST_OBJECT_LOCK (task);
301 while (G_UNLIKELY (GST_TASK_STATE (task) == GST_TASK_PAUSED)) {
304 t = g_static_rec_mutex_unlock_full (lock);
306 g_warning ("wrong STREAM_LOCK count %d", t);
308 GST_TASK_SIGNAL (task);
309 GST_TASK_WAIT (task);
310 GST_OBJECT_UNLOCK (task);
311 /* locking order.. */
313 g_static_rec_mutex_lock_full (lock, t);
315 GST_OBJECT_LOCK (task);
316 if (G_UNLIKELY (GET_TASK_STATE (task) == GST_TASK_STOPPED)) {
317 GST_OBJECT_UNLOCK (task);
321 GST_OBJECT_UNLOCK (task);
324 task->func (task->data);
327 g_static_rec_mutex_unlock (lock);
329 GST_OBJECT_LOCK (task);
330 task->abidata.ABI.thread = NULL;
333 if (priv->thr_callbacks.leave_thread) {
334 /* fire the leave_thread callback when we need to. We need to do this before
335 * we signal the task and with the task lock released. */
336 GST_OBJECT_UNLOCK (task);
337 priv->thr_callbacks.leave_thread (task, tself, priv->thr_user_data);
338 GST_OBJECT_LOCK (task);
340 /* restore normal priority when releasing back into the pool, we will not
341 * touch the priority when a custom callback has been installed. */
342 #if !GLIB_CHECK_VERSION (2, 31, 0)
343 g_thread_set_priority (tself, G_THREAD_PRIORITY_NORMAL);
346 /* now we allow messing with the lock again by setting the running flag to
347 * FALSE. Together with the SIGNAL this is the sign for the _join() to
349 * Note that we still have not dropped the final ref on the task. We could
350 * check here if there is a pending join() going on and drop the last ref
351 * before releasing the lock as we can be sure that a ref is held by the
352 * caller of the join(). */
353 task->running = FALSE;
354 GST_TASK_SIGNAL (task);
355 GST_OBJECT_UNLOCK (task);
357 GST_DEBUG ("Exit task %p, thread %p", task, g_thread_self ());
359 gst_object_unref (task);
364 g_warning ("starting task without a lock");
370 * gst_task_cleanup_all:
372 * Wait for all tasks to be stopped. This is mainly used internally
373 * to ensure proper cleanup of internal data structures in test suites.
378 gst_task_cleanup_all (void)
382 if ((klass = g_type_class_peek (GST_TYPE_TASK))) {
383 init_klass_pool (klass);
389 * @func: The #GstTaskFunction to use
390 * @data: (closure): User data to pass to @func
392 * Create a new Task that will repeatedly call the provided @func
393 * with @data as a parameter. Typically the task will run in
396 * The function cannot be changed after the task has been created. You
397 * must create a new #GstTask to change the function.
399 * This function will not yet create and start a thread. Use gst_task_start() or
400 * gst_task_pause() to create and start the GThread.
402 * Before the task can be used, a #GStaticRecMutex must be configured using the
403 * gst_task_set_lock() function. This lock will always be acquired while
406 * Returns: (transfer full): A new #GstTask.
411 gst_task_create (GstTaskFunction func, gpointer data)
415 task = g_object_newv (GST_TYPE_TASK, 0, NULL);
419 GST_DEBUG ("Created task %p", task);
426 * @task: The #GstTask to use
427 * @mutex: The #GMutex to use
429 * Set the mutex used by the task. The mutex will be acquired before
430 * calling the #GstTaskFunction.
432 * This function has to be called before calling gst_task_pause() or
438 gst_task_set_lock (GstTask * task, GStaticRecMutex * mutex)
440 GST_OBJECT_LOCK (task);
441 if (G_UNLIKELY (task->running))
443 GST_TASK_GET_LOCK (task) = mutex;
444 GST_OBJECT_UNLOCK (task);
451 GST_OBJECT_UNLOCK (task);
452 g_warning ("cannot call set_lock on a running task");
457 * gst_task_set_priority:
459 * @priority: a new priority for @task
461 * Changes the priority of @task to @priority.
463 * Note: try not to depend on task priorities.
470 gst_task_set_priority (GstTask * task, GThreadPriority priority)
472 GstTaskPrivate *priv;
475 g_return_if_fail (GST_IS_TASK (task));
479 GST_OBJECT_LOCK (task);
480 priv->prio_set = TRUE;
481 priv->priority = priority;
482 thread = task->abidata.ABI.thread;
483 if (thread != NULL) {
484 /* if this task already has a thread, we can configure the priority right
485 * away, else we do that when we assign a thread to the task. */
486 #if !GLIB_CHECK_VERSION (2, 31, 0)
487 g_thread_set_priority (thread, priority);
489 GST_INFO_OBJECT (task, "Thread priorities no longer have any effect");
492 GST_OBJECT_UNLOCK (task);
499 * Get the #GstTaskPool that this task will use for its streaming
504 * Returns: (transfer full): the #GstTaskPool used by @task. gst_object_unref()
510 gst_task_get_pool (GstTask * task)
513 GstTaskPrivate *priv;
515 g_return_val_if_fail (GST_IS_TASK (task), NULL);
519 GST_OBJECT_LOCK (task);
520 result = gst_object_ref (priv->pool);
521 GST_OBJECT_UNLOCK (task);
529 * @pool: (transfer none): a #GstTaskPool
531 * Set @pool as the new GstTaskPool for @task. Any new streaming threads that
532 * will be created by @task will now use @pool.
539 gst_task_set_pool (GstTask * task, GstTaskPool * pool)
542 GstTaskPrivate *priv;
544 g_return_if_fail (GST_IS_TASK (task));
545 g_return_if_fail (GST_IS_TASK_POOL (pool));
549 GST_OBJECT_LOCK (task);
550 if (priv->pool != pool) {
552 priv->pool = gst_object_ref (pool);
555 GST_OBJECT_UNLOCK (task);
558 gst_object_unref (old);
563 * gst_task_set_thread_callbacks:
564 * @task: The #GstTask to use
565 * @callbacks: (in): a #GstTaskThreadCallbacks pointer
566 * @user_data: (closure): user data passed to the callbacks
567 * @notify: called when @user_data is no longer referenced
569 * Set callbacks which will be executed when a new thread is needed, the thread
570 * function is entered and left and when the thread is joined.
572 * By default a thread for @task will be created from a default thread pool.
574 * Objects can use custom GThreads or can perform additional configuration of
575 * the threads (such as changing the thread priority) by installing callbacks.
582 gst_task_set_thread_callbacks (GstTask * task,
583 GstTaskThreadCallbacks * callbacks, gpointer user_data,
584 GDestroyNotify notify)
586 GDestroyNotify old_notify;
588 g_return_if_fail (task != NULL);
589 g_return_if_fail (GST_IS_TASK (task));
590 g_return_if_fail (callbacks != NULL);
592 GST_OBJECT_LOCK (task);
593 old_notify = task->priv->thr_notify;
598 old_data = task->priv->thr_user_data;
600 task->priv->thr_user_data = NULL;
601 task->priv->thr_notify = NULL;
602 GST_OBJECT_UNLOCK (task);
604 old_notify (old_data);
606 GST_OBJECT_LOCK (task);
608 task->priv->thr_callbacks = *callbacks;
609 task->priv->thr_user_data = user_data;
610 task->priv->thr_notify = notify;
611 GST_OBJECT_UNLOCK (task);
615 * gst_task_get_state:
616 * @task: The #GstTask to query
618 * Get the current state of the task.
620 * Returns: The #GstTaskState of the task
625 gst_task_get_state (GstTask * task)
629 g_return_val_if_fail (GST_IS_TASK (task), GST_TASK_STOPPED);
631 result = GET_TASK_STATE (task);
636 /* make sure the task is running and start a thread if it's not.
637 * This function must be called with the task LOCK. */
639 start_task (GstTask * task)
642 GError *error = NULL;
643 GstTaskPrivate *priv;
647 /* new task, We ref before so that it remains alive while
648 * the thread is running. */
649 gst_object_ref (task);
650 /* mark task as running so that a join will wait until we schedule
651 * and exit the task function. */
652 task->running = TRUE;
654 /* push on the thread pool, we remember the original pool because the user
655 * could change it later on and then we join to the wrong pool. */
656 priv->pool_id = gst_object_ref (priv->pool);
658 gst_task_pool_push (priv->pool_id, (GstTaskPoolFunction) gst_task_func,
662 g_warning ("failed to create thread: %s", error->message);
663 g_error_free (error);
671 * gst_task_set_state:
673 * @state: the new task state
675 * Sets the state of @task to @state.
677 * The @task must have a lock associated with it using
678 * gst_task_set_lock() when going to GST_TASK_STARTED or GST_TASK_PAUSED or
679 * this function will return %FALSE.
683 * Returns: %TRUE if the state could be changed.
688 gst_task_set_state (GstTask * task, GstTaskState state)
693 g_return_val_if_fail (GST_IS_TASK (task), FALSE);
695 GST_DEBUG_OBJECT (task, "Changing task %p to state %d", task, state);
697 GST_OBJECT_LOCK (task);
698 if (state != GST_TASK_STOPPED)
699 if (G_UNLIKELY (GST_TASK_GET_LOCK (task) == NULL))
702 /* if the state changed, do our thing */
703 old = GET_TASK_STATE (task);
705 SET_TASK_STATE (task, state);
707 case GST_TASK_STOPPED:
708 /* If the task already has a thread scheduled we don't have to do
710 if (G_UNLIKELY (!task->running))
711 res = start_task (task);
713 case GST_TASK_PAUSED:
714 /* when we are paused, signal to go to the new state */
715 GST_TASK_SIGNAL (task);
717 case GST_TASK_STARTED:
718 /* if we were started, we'll go to the new state after the next
723 GST_OBJECT_UNLOCK (task);
730 GST_WARNING_OBJECT (task, "state %d set on task without a lock", state);
731 GST_OBJECT_UNLOCK (task);
732 g_warning ("task without a lock can't be set to state %d", state);
739 * @task: The #GstTask to start
741 * Starts @task. The @task must have a lock associated with it using
742 * gst_task_set_lock() or this function will return %FALSE.
744 * Returns: %TRUE if the task could be started.
749 gst_task_start (GstTask * task)
751 return gst_task_set_state (task, GST_TASK_STARTED);
756 * @task: The #GstTask to stop
758 * Stops @task. This method merely schedules the task to stop and
759 * will not wait for the task to have completely stopped. Use
760 * gst_task_join() to stop and wait for completion.
762 * Returns: %TRUE if the task could be stopped.
767 gst_task_stop (GstTask * task)
769 return gst_task_set_state (task, GST_TASK_STOPPED);
774 * @task: The #GstTask to pause
776 * Pauses @task. This method can also be called on a task in the
777 * stopped state, in which case a thread will be started and will remain
778 * in the paused state. This function does not wait for the task to complete
781 * Returns: %TRUE if the task could be paused.
786 gst_task_pause (GstTask * task)
788 return gst_task_set_state (task, GST_TASK_PAUSED);
793 * @task: The #GstTask to join
795 * Joins @task. After this call, it is safe to unref the task
796 * and clean up the lock set with gst_task_set_lock().
798 * The task will automatically be stopped with this call.
800 * This function cannot be called from within a task function as this
801 * would cause a deadlock. The function will detect this and print a
804 * Returns: %TRUE if the task could be joined.
809 gst_task_join (GstTask * task)
812 GstTaskPrivate *priv;
814 GstTaskPool *pool = NULL;
818 g_return_val_if_fail (GST_IS_TASK (task), FALSE);
820 tself = g_thread_self ();
822 GST_DEBUG_OBJECT (task, "Joining task %p, thread %p", task, tself);
824 /* we don't use a real thread join here because we are using
826 GST_OBJECT_LOCK (task);
827 if (G_UNLIKELY (tself == task->abidata.ABI.thread))
829 SET_TASK_STATE (task, GST_TASK_STOPPED);
830 /* signal the state change for when it was blocked in PAUSED. */
831 GST_TASK_SIGNAL (task);
832 /* we set the running flag when pushing the task on the thread pool.
833 * This means that the task function might not be called when we try
834 * to join it here. */
835 while (G_LIKELY (task->running))
836 GST_TASK_WAIT (task);
837 /* clean the thread */
838 task->abidata.ABI.thread = NULL;
839 /* get the id and pool to join */
840 pool = priv->pool_id;
842 priv->pool_id = NULL;
844 GST_OBJECT_UNLOCK (task);
848 gst_task_pool_join (pool, id);
849 gst_object_unref (pool);
852 GST_DEBUG_OBJECT (task, "Joined task %p", task);
859 GST_WARNING_OBJECT (task, "trying to join task from its thread");
860 GST_OBJECT_UNLOCK (task);
861 g_warning ("\nTrying to join task %p from its thread would deadlock.\n"
862 "You cannot change the state of an element from its streaming\n"
863 "thread. Use g_idle_add() or post a GstMessage on the bus to\n"
864 "schedule the state change from the main thread.\n", task);