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DEFINITIONS
This source file includes following definitions.
- init_klass_pool
- gst_task_class_init
- gst_task_init
- gst_task_finalize
- gst_task_configure_name
- gst_task_func
- gst_task_cleanup_all
- gst_task_create
- gst_task_set_lock
- gst_task_set_priority
- gst_task_get_pool
- gst_task_set_pool
- gst_task_set_thread_callbacks
- gst_task_get_state
- start_task
- gst_task_set_state
- gst_task_start
- gst_task_stop
- gst_task_pause
- gst_task_join
/* GStreamer
* Copyright (C) 1999,2000 Erik Walthinsen <omega@cse.ogi.edu>
* 2005 Wim Taymans <wim@fluendo.com>
*
* gsttask.c: Streaming tasks
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Library General Public License for more details.
*
* You should have received a copy of the GNU Library General Public
* License along with this library; if not, write to the
* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
* Boston, MA 02111-1307, USA.
*/
/**
* SECTION:gsttask
* @short_description: Abstraction of GStreamer streaming threads.
* @see_also: #GstElement, #GstPad
*
* #GstTask is used by #GstElement and #GstPad to provide the data passing
* threads in a #GstPipeline.
*
* A #GstPad will typically start a #GstTask to push or pull data to/from the
* peer pads. Most source elements start a #GstTask to push data. In some cases
* a demuxer element can start a #GstTask to pull data from a peer element. This
* is typically done when the demuxer can perform random access on the upstream
* peer element for improved performance.
*
* Although convenience functions exist on #GstPad to start/pause/stop tasks, it
* might sometimes be needed to create a #GstTask manually if it is not related to
* a #GstPad.
*
* Before the #GstTask can be run, it needs a #GStaticRecMutex that can be set with
* gst_task_set_lock().
*
* The task can be started, paused and stopped with gst_task_start(), gst_task_pause()
* and gst_task_stop() respectively or with the gst_task_set_state() function.
*
* A #GstTask will repeatedly call the #GstTaskFunction with the user data
* that was provided when creating the task with gst_task_create(). While calling
* the function it will acquire the provided lock. The provided lock is released
* when the task pauses or stops.
*
* Stopping a task with gst_task_stop() will not immediately make sure the task is
* not running anymore. Use gst_task_join() to make sure the task is completely
* stopped and the thread is stopped.
*
* After creating a #GstTask, use gst_object_unref() to free its resources. This can
* only be done it the task is not running anymore.
*
* Task functions can send a #GstMessage to send out-of-band data to the
* application. The application can receive messages from the #GstBus in its
* mainloop.
*
* For debugging perposes, the task will configure its object name as the thread
* name on Linux. Please note that the object name should be configured before the
* task is started; changing the object name after the task has been started, has
* no effect on the thread name.
*
* Last reviewed on 2010-03-15 (0.10.29)
*/
#include "gst_private.h"
#include "gstinfo.h"
#include "gsttask.h"
#include <stdio.h>
#ifdef HAVE_SYS_PRCTL_H
#include <sys/prctl.h>
#endif
GST_DEBUG_CATEGORY_STATIC (task_debug);
#define GST_CAT_DEFAULT (task_debug)
#define GST_TASK_GET_PRIVATE(obj) \
(G_TYPE_INSTANCE_GET_PRIVATE ((obj), GST_TYPE_TASK, GstTaskPrivate))
struct _GstTaskPrivate
{
/* callbacks for managing the thread of this task */
GstTaskThreadCallbacks thr_callbacks;
gpointer thr_user_data;
GDestroyNotify thr_notify;
gboolean prio_set;
GThreadPriority priority;
/* configured pool */
GstTaskPool *pool;
/* remember the pool and id that is currently running. */
gpointer id;
GstTaskPool *pool_id;
};
static void gst_task_finalize (GObject * object);
static void gst_task_func (GstTask * task);
static GStaticMutex pool_lock = G_STATIC_MUTEX_INIT;
#define _do_init \
{ \
GST_DEBUG_CATEGORY_INIT (task_debug, "task", 0, "Processing tasks"); \
}
G_DEFINE_TYPE_WITH_CODE (GstTask, gst_task, GST_TYPE_OBJECT, _do_init);
static void
init_klass_pool (GstTaskClass * klass)
{
g_static_mutex_lock (&pool_lock);
if (klass->pool) {
gst_task_pool_cleanup (klass->pool);
gst_object_unref (klass->pool);
}
klass->pool = gst_task_pool_new ();
gst_task_pool_prepare (klass->pool, NULL);
g_static_mutex_unlock (&pool_lock);
}
static void
gst_task_class_init (GstTaskClass * klass)
{
GObjectClass *gobject_class;
gobject_class = (GObjectClass *) klass;
g_type_class_add_private (klass, sizeof (GstTaskPrivate));
gobject_class->finalize = gst_task_finalize;
init_klass_pool (klass);
}
static void
gst_task_init (GstTask * task)
{
GstTaskClass *klass;
klass = GST_TASK_GET_CLASS (task);
task->priv = GST_TASK_GET_PRIVATE (task);
task->running = FALSE;
task->abidata.ABI.thread = NULL;
task->lock = NULL;
task->cond = g_cond_new ();
task->state = GST_TASK_STOPPED;
task->priv->prio_set = FALSE;
/* use the default klass pool for this task, users can
* override this later */
g_static_mutex_lock (&pool_lock);
task->priv->pool = gst_object_ref (klass->pool);
g_static_mutex_unlock (&pool_lock);
}
static void
gst_task_finalize (GObject * object)
{
GstTask *task = GST_TASK (object);
GstTaskPrivate *priv = task->priv;
GST_DEBUG ("task %p finalize", task);
if (priv->thr_notify)
priv->thr_notify (priv->thr_user_data);
priv->thr_notify = NULL;
priv->thr_user_data = NULL;
gst_object_unref (priv->pool);
/* task thread cannot be running here since it holds a ref
* to the task so that the finalize could not have happened */
g_cond_free (task->cond);
task->cond = NULL;
G_OBJECT_CLASS (gst_task_parent_class)->finalize (object);
}
/* should be called with the object LOCK */
static void
gst_task_configure_name (GstTask * task)
{
#ifdef HAVE_SYS_PRCTL_H
const gchar *name;
gchar thread_name[17] = { 0, };
name = GST_OBJECT_NAME (task);
/* set the thread name to something easily identifiable */
if (!snprintf (thread_name, 17, "%s", GST_STR_NULL (name))) {
GST_DEBUG_OBJECT (task, "Could not create thread name for '%s'", name);
} else {
GST_DEBUG_OBJECT (task, "Setting thread name to '%s'", thread_name);
if (prctl (PR_SET_NAME, (unsigned long int) thread_name, 0, 0, 0))
GST_DEBUG_OBJECT (task, "Failed to set thread name");
}
#endif
}
static void
gst_task_func (GstTask * task)
{
GStaticRecMutex *lock;
GThread *tself;
GstTaskPrivate *priv;
priv = task->priv;
tself = g_thread_self ();
GST_DEBUG ("Entering task %p, thread %p", task, tself);
/* we have to grab the lock to get the mutex. We also
* mark our state running so that nobody can mess with
* the mutex. */
GST_OBJECT_LOCK (task);
if (task->state == GST_TASK_STOPPED)
goto exit;
lock = GST_TASK_GET_LOCK (task);
if (G_UNLIKELY (lock == NULL))
goto no_lock;
task->abidata.ABI.thread = tself;
/* only update the priority when it was changed */
if (priv->prio_set)
g_thread_set_priority (tself, priv->priority);
GST_OBJECT_UNLOCK (task);
/* fire the enter_thread callback when we need to */
if (priv->thr_callbacks.enter_thread)
priv->thr_callbacks.enter_thread (task, tself, priv->thr_user_data);
/* locking order is TASK_LOCK, LOCK */
g_static_rec_mutex_lock (lock);
GST_OBJECT_LOCK (task);
/* configure the thread name now */
gst_task_configure_name (task);
while (G_LIKELY (task->state != GST_TASK_STOPPED)) {
while (G_UNLIKELY (task->state == GST_TASK_PAUSED)) {
gint t;
t = g_static_rec_mutex_unlock_full (lock);
if (t <= 0) {
g_warning ("wrong STREAM_LOCK count %d", t);
}
GST_TASK_SIGNAL (task);
GST_TASK_WAIT (task);
GST_OBJECT_UNLOCK (task);
/* locking order.. */
if (t > 0)
g_static_rec_mutex_lock_full (lock, t);
GST_OBJECT_LOCK (task);
if (G_UNLIKELY (task->state == GST_TASK_STOPPED))
goto done;
}
GST_OBJECT_UNLOCK (task);
task->func (task->data);
GST_OBJECT_LOCK (task);
}
done:
GST_OBJECT_UNLOCK (task);
g_static_rec_mutex_unlock (lock);
GST_OBJECT_LOCK (task);
task->abidata.ABI.thread = NULL;
exit:
if (priv->thr_callbacks.leave_thread) {
/* fire the leave_thread callback when we need to. We need to do this before
* we signal the task and with the task lock released. */
GST_OBJECT_UNLOCK (task);
priv->thr_callbacks.leave_thread (task, tself, priv->thr_user_data);
GST_OBJECT_LOCK (task);
} else {
/* restore normal priority when releasing back into the pool, we will not
* touch the priority when a custom callback has been installed. */
g_thread_set_priority (tself, G_THREAD_PRIORITY_NORMAL);
}
/* now we allow messing with the lock again by setting the running flag to
* FALSE. Together with the SIGNAL this is the sign for the _join() to
* complete.
* Note that we still have not dropped the final ref on the task. We could
* check here if there is a pending join() going on and drop the last ref
* before releasing the lock as we can be sure that a ref is held by the
* caller of the join(). */
task->running = FALSE;
GST_TASK_SIGNAL (task);
GST_OBJECT_UNLOCK (task);
GST_DEBUG ("Exit task %p, thread %p", task, g_thread_self ());
gst_object_unref (task);
return;
no_lock:
{
g_warning ("starting task without a lock");
goto exit;
}
}
/**
* gst_task_cleanup_all:
*
* Wait for all tasks to be stopped. This is mainly used internally
* to ensure proper cleanup of internal data structures in test suites.
*
* MT safe.
*/
void
gst_task_cleanup_all (void)
{
GstTaskClass *klass;
if ((klass = g_type_class_peek (GST_TYPE_TASK))) {
init_klass_pool (klass);
}
}
/**
* gst_task_create:
* @func: The #GstTaskFunction to use
* @data: User data to pass to @func
*
* Create a new Task that will repeatedly call the provided @func
* with @data as a parameter. Typically the task will run in
* a new thread.
*
* The function cannot be changed after the task has been created. You
* must create a new #GstTask to change the function.
*
* This function will not yet create and start a thread. Use gst_task_start() or
* gst_task_pause() to create and start the GThread.
*
* Before the task can be used, a #GStaticRecMutex must be configured using the
* gst_task_set_lock() function. This lock will always be acquired while
* @func is called.
*
* Returns: A new #GstTask.
*
* MT safe.
*/
GstTask *
gst_task_create (GstTaskFunction func, gpointer data)
{
GstTask *task;
task = g_object_newv (GST_TYPE_TASK, 0, NULL);
task->func = func;
task->data = data;
GST_DEBUG ("Created task %p", task);
return task;
}
/**
* gst_task_set_lock:
* @task: The #GstTask to use
* @mutex: The #GMutex to use
*
* Set the mutex used by the task. The mutex will be acquired before
* calling the #GstTaskFunction.
*
* This function has to be called before calling gst_task_pause() or
* gst_task_start().
*
* MT safe.
*/
void
gst_task_set_lock (GstTask * task, GStaticRecMutex * mutex)
{
GST_OBJECT_LOCK (task);
if (G_UNLIKELY (task->running))
goto is_running;
GST_TASK_GET_LOCK (task) = mutex;
GST_OBJECT_UNLOCK (task);
return;
/* ERRORS */
is_running:
{
GST_OBJECT_UNLOCK (task);
g_warning ("cannot call set_lock on a running task");
}
}
/**
* gst_task_set_priority:
* @task: a #GstTask
* @priority: a new priority for @task
*
* Changes the priority of @task to @priority.
*
* Note: try not to depend on task priorities.
*
* MT safe.
*
* Since: 0.10.24
*/
void
gst_task_set_priority (GstTask * task, GThreadPriority priority)
{
GstTaskPrivate *priv;
GThread *thread;
g_return_if_fail (GST_IS_TASK (task));
priv = task->priv;
GST_OBJECT_LOCK (task);
priv->prio_set = TRUE;
priv->priority = priority;
thread = task->abidata.ABI.thread;
if (thread != NULL) {
/* if this task already has a thread, we can configure the priority right
* away, else we do that when we assign a thread to the task. */
g_thread_set_priority (thread, priority);
}
GST_OBJECT_UNLOCK (task);
}
/**
* gst_task_get_pool:
* @task: a #GstTask
*
* Get the #GstTaskPool that this task will use for its streaming
* threads.
*
* MT safe.
*
* Returns: the #GstTaskPool used by @task. gst_object_unref()
* after usage.
*
* Since: 0.10.24
*/
GstTaskPool *
gst_task_get_pool (GstTask * task)
{
GstTaskPool *result;
GstTaskPrivate *priv;
g_return_val_if_fail (GST_IS_TASK (task), NULL);
priv = task->priv;
GST_OBJECT_LOCK (task);
result = gst_object_ref (priv->pool);
GST_OBJECT_UNLOCK (task);
return result;
}
/**
* gst_task_set_pool:
* @task: a #GstTask
* @pool: a #GstTaskPool
*
* Set @pool as the new GstTaskPool for @task. Any new streaming threads that
* will be created by @task will now use @pool.
*
* MT safe.
*
* Since: 0.10.24
*/
void
gst_task_set_pool (GstTask * task, GstTaskPool * pool)
{
GstTaskPool *old;
GstTaskPrivate *priv;
g_return_if_fail (GST_IS_TASK (task));
g_return_if_fail (GST_IS_TASK_POOL (pool));
priv = task->priv;
GST_OBJECT_LOCK (task);
if (priv->pool != pool) {
old = priv->pool;
priv->pool = gst_object_ref (pool);
} else
old = NULL;
GST_OBJECT_UNLOCK (task);
if (old)
gst_object_unref (old);
}
/**
* gst_task_set_thread_callbacks:
* @task: The #GstTask to use
* @callbacks: a #GstTaskThreadCallbacks pointer
* @user_data: user data passed to the callbacks
* @notify: called when @user_data is no longer referenced
*
* Set callbacks which will be executed when a new thread is needed, the thread
* function is entered and left and when the thread is joined.
*
* By default a thread for @task will be created from a default thread pool.
*
* Objects can use custom GThreads or can perform additional configuration of
* the threads (such as changing the thread priority) by installing callbacks.
*
* MT safe.
*
* Since: 0.10.24
*/
void
gst_task_set_thread_callbacks (GstTask * task,
GstTaskThreadCallbacks * callbacks, gpointer user_data,
GDestroyNotify notify)
{
GDestroyNotify old_notify;
g_return_if_fail (task != NULL);
g_return_if_fail (GST_IS_TASK (task));
g_return_if_fail (callbacks != NULL);
GST_OBJECT_LOCK (task);
old_notify = task->priv->thr_notify;
if (old_notify) {
gpointer old_data;
old_data = task->priv->thr_user_data;
task->priv->thr_user_data = NULL;
task->priv->thr_notify = NULL;
GST_OBJECT_UNLOCK (task);
old_notify (old_data);
GST_OBJECT_LOCK (task);
}
task->priv->thr_callbacks = *callbacks;
task->priv->thr_user_data = user_data;
task->priv->thr_notify = notify;
GST_OBJECT_UNLOCK (task);
}
/**
* gst_task_get_state:
* @task: The #GstTask to query
*
* Get the current state of the task.
*
* Returns: The #GstTaskState of the task
*
* MT safe.
*/
GstTaskState
gst_task_get_state (GstTask * task)
{
GstTaskState result;
g_return_val_if_fail (GST_IS_TASK (task), GST_TASK_STOPPED);
GST_OBJECT_LOCK (task);
result = task->state;
GST_OBJECT_UNLOCK (task);
return result;
}
/* make sure the task is running and start a thread if it's not.
* This function must be called with the task LOCK. */
static gboolean
start_task (GstTask * task)
{
gboolean res = TRUE;
GError *error = NULL;
GstTaskPrivate *priv;
priv = task->priv;
/* new task, We ref before so that it remains alive while
* the thread is running. */
gst_object_ref (task);
/* mark task as running so that a join will wait until we schedule
* and exit the task function. */
task->running = TRUE;
/* push on the thread pool, we remember the original pool because the user
* could change it later on and then we join to the wrong pool. */
priv->pool_id = gst_object_ref (priv->pool);
priv->id =
gst_task_pool_push (priv->pool_id, (GstTaskPoolFunction) gst_task_func,
task, &error);
if (error != NULL) {
g_warning ("failed to create thread: %s", error->message);
g_error_free (error);
res = FALSE;
}
return res;
}
/**
* gst_task_set_state:
* @task: a #GstTask
* @state: the new task state
*
* Sets the state of @task to @state.
*
* The @task must have a lock associated with it using
* gst_task_set_lock() when going to GST_TASK_STARTED or GST_TASK_PAUSED or
* this function will return %FALSE.
*
* MT safe.
*
* Returns: %TRUE if the state could be changed.
*
* Since: 0.10.24
*/
gboolean
gst_task_set_state (GstTask * task, GstTaskState state)
{
GstTaskState old;
gboolean res = TRUE;
g_return_val_if_fail (GST_IS_TASK (task), FALSE);
GST_DEBUG_OBJECT (task, "Changing task %p to state %d", task, state);
GST_OBJECT_LOCK (task);
if (state != GST_TASK_STOPPED)
if (G_UNLIKELY (GST_TASK_GET_LOCK (task) == NULL))
goto no_lock;
/* if the state changed, do our thing */
old = task->state;
if (old != state) {
task->state = state;
switch (old) {
case GST_TASK_STOPPED:
/* If the task already has a thread scheduled we don't have to do
* anything. */
if (G_UNLIKELY (!task->running))
res = start_task (task);
break;
case GST_TASK_PAUSED:
/* when we are paused, signal to go to the new state */
GST_TASK_SIGNAL (task);
break;
case GST_TASK_STARTED:
/* if we were started, we'll go to the new state after the next
* iteration. */
break;
}
}
GST_OBJECT_UNLOCK (task);
return res;
/* ERRORS */
no_lock:
{
GST_WARNING_OBJECT (task, "state %d set on task without a lock", state);
GST_OBJECT_UNLOCK (task);
g_warning ("task without a lock can't be set to state %d", state);
return FALSE;
}
}
/**
* gst_task_start:
* @task: The #GstTask to start
*
* Starts @task. The @task must have a lock associated with it using
* gst_task_set_lock() or this function will return %FALSE.
*
* Returns: %TRUE if the task could be started.
*
* MT safe.
*/
gboolean
gst_task_start (GstTask * task)
{
return gst_task_set_state (task, GST_TASK_STARTED);
}
/**
* gst_task_stop:
* @task: The #GstTask to stop
*
* Stops @task. This method merely schedules the task to stop and
* will not wait for the task to have completely stopped. Use
* gst_task_join() to stop and wait for completion.
*
* Returns: %TRUE if the task could be stopped.
*
* MT safe.
*/
gboolean
gst_task_stop (GstTask * task)
{
return gst_task_set_state (task, GST_TASK_STOPPED);
}
/**
* gst_task_pause:
* @task: The #GstTask to pause
*
* Pauses @task. This method can also be called on a task in the
* stopped state, in which case a thread will be started and will remain
* in the paused state. This function does not wait for the task to complete
* the paused state.
*
* Returns: %TRUE if the task could be paused.
*
* MT safe.
*/
gboolean
gst_task_pause (GstTask * task)
{
return gst_task_set_state (task, GST_TASK_PAUSED);
}
/**
* gst_task_join:
* @task: The #GstTask to join
*
* Joins @task. After this call, it is safe to unref the task
* and clean up the lock set with gst_task_set_lock().
*
* The task will automatically be stopped with this call.
*
* This function cannot be called from within a task function as this
* would cause a deadlock. The function will detect this and print a
* g_warning.
*
* Returns: %TRUE if the task could be joined.
*
* MT safe.
*/
gboolean
gst_task_join (GstTask * task)
{
GThread *tself;
GstTaskPrivate *priv;
gpointer id;
GstTaskPool *pool = NULL;
priv = task->priv;
g_return_val_if_fail (GST_IS_TASK (task), FALSE);
tself = g_thread_self ();
GST_DEBUG_OBJECT (task, "Joining task %p, thread %p", task, tself);
/* we don't use a real thread join here because we are using
* thread pools */
GST_OBJECT_LOCK (task);
if (G_UNLIKELY (tself == task->abidata.ABI.thread))
goto joining_self;
task->state = GST_TASK_STOPPED;
/* signal the state change for when it was blocked in PAUSED. */
GST_TASK_SIGNAL (task);
/* we set the running flag when pushing the task on the thread pool.
* This means that the task function might not be called when we try
* to join it here. */
while (G_LIKELY (task->running))
GST_TASK_WAIT (task);
/* clean the thread */
task->abidata.ABI.thread = NULL;
/* get the id and pool to join */
pool = priv->pool_id;
id = priv->id;
priv->pool_id = NULL;
priv->id = NULL;
GST_OBJECT_UNLOCK (task);
if (pool) {
if (id)
gst_task_pool_join (pool, id);
gst_object_unref (pool);
}
GST_DEBUG_OBJECT (task, "Joined task %p", task);
return TRUE;
/* ERRORS */
joining_self:
{
GST_WARNING_OBJECT (task, "trying to join task from its thread");
GST_OBJECT_UNLOCK (task);
g_warning ("\nTrying to join task %p from its thread would deadlock.\n"
"You cannot change the state of an element from its streaming\n"
"thread. Use g_idle_add() or post a GstMessage on the bus to\n"
"schedule the state change from the main thread.\n", task);
return FALSE;
}
}