gstreamer/gst/gsttask.c
Wim Taymans f0f388b8ba gst/gstpad.c: Improve debugging for task functions.
Original commit message from CVS:
* gst/gstpad.c: (gst_pad_start_task), (gst_pad_pause_task),
(gst_pad_stop_task):
Improve debugging for task functions.
* gst/gsttask.c: (gst_task_func), (gst_task_set_lock),
(gst_task_start), (gst_task_pause), (gst_task_join):
Make sure that the task function started and finished after a
join().
Don't try to push the task function on the threadpool multiple
times.
Improve the g_warning message with some useful suggestions
about how to fix the problem.
2006-08-23 16:51:19 +00:00

579 lines
14 KiB
C

/* 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.
*
* A #GstTask will repeadedly call the #GstTaskFunction with the user data
* that was provided when creating the task with gst_task_create(). Before calling
* the function it will acquire the provided lock.
*
* Stopping a task with gst_task_stop() will not immediatly 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.
*
* Last reviewed on 2006-02-13 (0.10.4)
*/
#include "gst_private.h"
#include "gstinfo.h"
#include "gsttask.h"
GST_DEBUG_CATEGORY_STATIC (task_debug);
#define GST_CAT_DEFAULT (task_debug)
static void gst_task_class_init (GstTaskClass * klass);
static void gst_task_init (GstTask * task);
static void gst_task_finalize (GObject * object);
static void gst_task_func (GstTask * task, GstTaskClass * tclass);
static GstObjectClass *parent_class = NULL;
static GStaticMutex pool_lock = G_STATIC_MUTEX_INIT;
GType
gst_task_get_type (void)
{
static GType _gst_task_type = 0;
if (G_UNLIKELY (_gst_task_type == 0)) {
static const GTypeInfo task_info = {
sizeof (GstTaskClass),
NULL,
NULL,
(GClassInitFunc) gst_task_class_init,
NULL,
NULL,
sizeof (GstTask),
0,
(GInstanceInitFunc) gst_task_init,
NULL
};
_gst_task_type =
g_type_register_static (GST_TYPE_OBJECT, "GstTask", &task_info, 0);
GST_DEBUG_CATEGORY_INIT (task_debug, "task", 0, "Processing tasks");
}
return _gst_task_type;
}
static void
gst_task_class_init (GstTaskClass * klass)
{
GObjectClass *gobject_class;
gobject_class = (GObjectClass *) klass;
parent_class = g_type_class_peek_parent (klass);
gobject_class->finalize = GST_DEBUG_FUNCPTR (gst_task_finalize);
klass->pool = g_thread_pool_new (
(GFunc) gst_task_func, klass, -1, FALSE, NULL);
}
static void
gst_task_init (GstTask * task)
{
task->running = FALSE;
task->abidata.ABI.thread = NULL;
task->lock = NULL;
task->cond = g_cond_new ();
task->state = GST_TASK_STOPPED;
}
static void
gst_task_finalize (GObject * object)
{
GstTask *task = GST_TASK (object);
GST_DEBUG ("task %p finalize", task);
/* 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 (parent_class)->finalize (object);
}
static void
gst_task_func (GstTask * task, GstTaskClass * tclass)
{
GStaticRecMutex *lock;
GThread *tself;
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;
GST_OBJECT_UNLOCK (task);
/* locking order is TASK_LOCK, LOCK */
g_static_rec_mutex_lock (lock);
GST_OBJECT_LOCK (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:
/* 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 datastructures in testsuites.
*
* MT safe.
*/
void
gst_task_cleanup_all (void)
{
GstTaskClass *klass;
if ((klass = g_type_class_peek (GST_TYPE_TASK))) {
g_static_mutex_lock (&pool_lock);
if (klass->pool) {
/* Shut down all the threads, we still process the ones scheduled
* because the unref happens in the thread function.
* Also wait for currently running ones to finish. */
g_thread_pool_free (klass->pool, FALSE, TRUE);
/* create new pool, so we can still do something after this
* call. */
klass->pool = g_thread_pool_new (
(GFunc) gst_task_func, klass, -1, FALSE, NULL);
}
g_static_mutex_unlock (&pool_lock);
}
}
/**
* gst_task_create:
* @func: The #GstTaskFunction to use
* @data: User data to pass to @func
*
* Create a new Task that will repeadedly 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.
*
* Returns: A new #GstTask.
*
* MT safe.
*/
GstTask *
gst_task_create (GstTaskFunction func, gpointer data)
{
GstTask *task;
task = g_object_new (GST_TYPE_TASK, 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_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;
}
/**
* 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 thsi function will return FALSE.
*
* Returns: TRUE if the task could be started.
*
* MT safe.
*/
gboolean
gst_task_start (GstTask * task)
{
GstTaskState old;
g_return_val_if_fail (GST_IS_TASK (task), FALSE);
GST_DEBUG_OBJECT (task, "Starting task %p", task);
GST_OBJECT_LOCK (task);
if (G_UNLIKELY (GST_TASK_GET_LOCK (task) == NULL))
goto no_lock;
old = task->state;
task->state = GST_TASK_STARTED;
switch (old) {
case GST_TASK_STOPPED:
{
GstTaskClass *tclass;
/* If the task already has a thread scheduled we don't have to do
* anything. */
if (task->running)
break;
/* new task, push on threadpool. We ref before so
* that it remains alive while on the threadpool. */
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;
tclass = GST_TASK_GET_CLASS (task);
g_static_mutex_lock (&pool_lock);
g_thread_pool_push (tclass->pool, task, NULL);
g_static_mutex_unlock (&pool_lock);
break;
}
case GST_TASK_PAUSED:
/* PAUSE to PLAY, signal */
GST_TASK_SIGNAL (task);
break;
case GST_TASK_STARTED:
/* was OK */
break;
}
GST_OBJECT_UNLOCK (task);
return TRUE;
/* ERRORS */
no_lock:
{
GST_WARNING_OBJECT (task, "starting task without a lock");
GST_OBJECT_UNLOCK (task);
g_warning ("starting task without a lock");
return FALSE;
}
}
/**
* 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)
{
GstTaskClass *tclass;
GstTaskState old;
g_return_val_if_fail (GST_IS_TASK (task), FALSE);
tclass = GST_TASK_GET_CLASS (task);
GST_DEBUG_OBJECT (task, "Stopping task %p", task);
GST_OBJECT_LOCK (task);
old = task->state;
task->state = GST_TASK_STOPPED;
switch (old) {
case GST_TASK_STOPPED:
break;
case GST_TASK_PAUSED:
GST_TASK_SIGNAL (task);
break;
case GST_TASK_STARTED:
break;
}
GST_OBJECT_UNLOCK (task);
return TRUE;
}
/**
* 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)
{
GstTaskState old;
g_return_val_if_fail (GST_IS_TASK (task), FALSE);
GST_DEBUG_OBJECT (task, "Pausing task %p", task);
GST_OBJECT_LOCK (task);
if (G_UNLIKELY (GST_TASK_GET_LOCK (task) == NULL))
goto no_lock;
old = task->state;
task->state = GST_TASK_PAUSED;
switch (old) {
case GST_TASK_STOPPED:
{
GstTaskClass *tclass;
if (task->running)
break;
gst_object_ref (task);
task->running = TRUE;
tclass = GST_TASK_GET_CLASS (task);
g_static_mutex_lock (&pool_lock);
g_thread_pool_push (tclass->pool, task, NULL);
g_static_mutex_unlock (&pool_lock);
break;
}
case GST_TASK_PAUSED:
break;
case GST_TASK_STARTED:
break;
}
GST_OBJECT_UNLOCK (task);
return TRUE;
/* ERRORS */
no_lock:
{
GST_WARNING_OBJECT (task, "pausing task without a lock");
GST_OBJECT_UNLOCK (task);
g_warning ("pausing task without a lock");
return FALSE;
}
}
/**
* 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;
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
* threadpools */
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 threadpool.
* 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);
GST_OBJECT_UNLOCK (task);
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;
}
}