Commit 8177173d authored by Sebastian Dröge's avatar Sebastian Dröge 🍵

element: Add gst_element_call_async()

This calls a function from another thread, asynchronously. This is to be
used for cases when a state change has to be performed from a streaming
thread, directly via gst_element_set_state() or indirectly e.g. via SEEK
events.

Calling those functions directly from the streaming thread will cause
deadlocks in many situations, as they might involve waiting for the
streaming thread to shut down from this very streaming thread.

This is mostly a convenience function around a GThreadPool and is for example
used by GstBin to continue asynchronous state changes.

https://bugzilla.gnome.org/show_bug.cgi?id=760532
parent a4db38ab
......@@ -917,6 +917,10 @@ gst_element_add_property_notify_watch
gst_element_add_property_deep_notify_watch
gst_element_remove_property_notify_watch
<SUBSECTION element-call-async>
GstElementCallAsyncFunc
gst_element_call_async
<SUBSECTION Standard>
GST_ELEMENT
GST_IS_ELEMENT
......
......@@ -201,7 +201,6 @@ struct _GstBinPrivate
typedef struct
{
GstBin *bin;
guint32 cookie;
GstState pending;
} BinContinueData;
......@@ -221,7 +220,7 @@ static GstStateChangeReturn gst_bin_get_state_func (GstElement * element,
static void bin_handle_async_done (GstBin * bin, GstStateChangeReturn ret,
gboolean flag_pending, GstClockTime running_time);
static void bin_handle_async_start (GstBin * bin);
static void bin_push_state_continue (BinContinueData * data);
static void bin_push_state_continue (GstBin * bin, BinContinueData * data);
static void bin_do_eos (GstBin * bin);
static gboolean gst_bin_add_func (GstBin * bin, GstElement * element);
......@@ -249,7 +248,7 @@ static gboolean gst_bin_do_latency_func (GstBin * bin);
static void bin_remove_messages (GstBin * bin, GstObject * src,
GstMessageType types);
static void gst_bin_continue_func (BinContinueData * data);
static void gst_bin_continue_func (GstBin * bin, BinContinueData * data);
static gint bin_element_is_sink (GstElement * child, GstBin * bin);
static gint bin_element_is_src (GstElement * child, GstBin * bin);
......@@ -358,7 +357,6 @@ gst_bin_class_init (GstBinClass * klass)
{
GObjectClass *gobject_class;
GstElementClass *gstelement_class;
GError *err;
gobject_class = (GObjectClass *) klass;
gstelement_class = (GstElementClass *) klass;
......@@ -470,14 +468,6 @@ gst_bin_class_init (GstBinClass * klass)
klass->handle_message = GST_DEBUG_FUNCPTR (gst_bin_handle_message_func);
klass->do_latency = GST_DEBUG_FUNCPTR (gst_bin_do_latency_func);
GST_DEBUG ("creating bin thread pool");
err = NULL;
klass->pool =
g_thread_pool_new ((GFunc) gst_bin_continue_func, NULL, -1, FALSE, &err);
if (err != NULL) {
g_critical ("could not alloc threadpool %s", err->message);
}
}
static void
......@@ -3025,13 +3015,11 @@ gst_bin_send_event (GstElement * element, GstEvent * event)
* their state, this function will attempt to bring the bin to the next state.
*/
static void
gst_bin_continue_func (BinContinueData * data)
gst_bin_continue_func (GstBin * bin, BinContinueData * data)
{
GstBin *bin;
GstState current, next, pending;
GstStateChange transition;
bin = data->bin;
pending = data->pending;
GST_DEBUG_OBJECT (bin, "waiting for state lock");
......@@ -3065,8 +3053,6 @@ gst_bin_continue_func (BinContinueData * data)
GST_STATE_UNLOCK (bin);
GST_DEBUG_OBJECT (bin, "state continue done");
gst_object_unref (bin);
g_slice_free (BinContinueData, data);
return;
interrupted:
......@@ -3074,8 +3060,6 @@ interrupted:
GST_OBJECT_UNLOCK (bin);
GST_STATE_UNLOCK (bin);
GST_DEBUG_OBJECT (bin, "state continue aborted due to intervening change");
gst_object_unref (bin);
g_slice_free (BinContinueData, data);
return;
}
}
......@@ -3095,17 +3079,18 @@ bin_bus_handler (GstBus * bus, GstMessage * message, GstBin * bin)
}
static void
bin_push_state_continue (BinContinueData * data)
free_bin_continue_data (BinContinueData * data)
{
GstBinClass *klass;
GstBin *bin;
/* ref was taken */
bin = data->bin;
klass = GST_BIN_GET_CLASS (bin);
g_slice_free (BinContinueData, data);
}
static void
bin_push_state_continue (GstBin * bin, BinContinueData * data)
{
GST_DEBUG_OBJECT (bin, "pushing continue on thread pool");
g_thread_pool_push (klass->pool, data, NULL);
gst_element_call_async (GST_ELEMENT_CAST (bin),
(GstElementCallAsyncFunc) gst_bin_continue_func, data,
(GDestroyNotify) free_bin_continue_data);
}
/* an element started an async state change, if we were not busy with a state
......@@ -3268,8 +3253,6 @@ bin_handle_async_done (GstBin * bin, GstStateChangeReturn ret,
cont = g_slice_new (BinContinueData);
/* ref to the bin */
cont->bin = gst_object_ref (bin);
/* cookie to detect concurrent state change */
cont->cookie = GST_ELEMENT_CAST (bin)->state_cookie;
/* pending target state */
......@@ -3300,7 +3283,7 @@ bin_handle_async_done (GstBin * bin, GstStateChangeReturn ret,
if (cont) {
/* toplevel, start continue state */
GST_DEBUG_OBJECT (bin, "all async-done, starting state continue");
bin_push_state_continue (cont);
bin_push_state_continue (bin, cont);
} else {
GST_DEBUG_OBJECT (bin, "state change complete");
GST_STATE_BROADCAST (bin);
......
......@@ -152,7 +152,7 @@ struct _GstBinClass {
GstElementClass parent_class;
/*< private >*/
GThreadPool *pool;
GThreadPool *pool; /* deprecated */
/* signals */
void (*element_added) (GstBin *bin, GstElement *child);
......
......@@ -147,9 +147,13 @@ static GstPadTemplate
* gst_element_class_get_request_pad_template (GstElementClass *
element_class, const gchar * name);
static void gst_element_call_async_func (gpointer data, gpointer user_data);
static GstObjectClass *parent_class = NULL;
static guint gst_element_signals[LAST_SIGNAL] = { 0 };
static GThreadPool *gst_element_pool = NULL;
/* this is used in gstelementfactory.c:gst_element_register() */
GQuark __gst_elementclass_factory = 0;
......@@ -187,6 +191,7 @@ static void
gst_element_class_init (GstElementClass * klass)
{
GObjectClass *gobject_class;
GError *err = NULL;
gobject_class = (GObjectClass *) klass;
......@@ -247,6 +252,15 @@ gst_element_class_init (GstElementClass * klass)
klass->set_context = GST_DEBUG_FUNCPTR (gst_element_set_context_default);
klass->elementfactory = NULL;
GST_DEBUG ("creating element thread pool");
gst_element_pool =
g_thread_pool_new ((GFunc) gst_element_call_async_func, NULL, -1, FALSE,
&err);
if (err != NULL) {
g_critical ("could not alloc threadpool %s", err->message);
g_clear_error (&err);
}
}
static void
......@@ -3364,3 +3378,60 @@ gst_element_remove_property_notify_watch (GstElement * element, gulong watch_id)
{
g_signal_handler_disconnect (element, watch_id);
}
typedef struct
{
GstElement *element;
GstElementCallAsyncFunc func;
gpointer user_data;
GDestroyNotify destroy_notify;
} GstElementCallAsyncData;
static void
gst_element_call_async_func (gpointer data, gpointer user_data)
{
GstElementCallAsyncData *async_data = data;
async_data->func (async_data->element, async_data->user_data);
if (async_data->destroy_notify)
async_data->destroy_notify (async_data->user_data);
gst_object_unref (async_data->element);
g_free (async_data);
}
/**
* gst_element_call_async:
* @element: a #GstElement
* @func: Function to call asynchronously from another thread
* @user_data: Data to pass to @func
* @destroy_notify: GDestroyNotify for @user_data
*
* Calls @func from another thread and passes @user_data to it. This is to be
* used for cases when a state change has to be performed from a streaming
* thread, directly via gst_element_set_state() or indirectly e.g. via SEEK
* events.
*
* Calling those functions directly from the streaming thread will cause
* deadlocks in many situations, as they might involve waiting for the
* streaming thread to shut down from this very streaming thread.
*
* MT safe.
*
* Since: 1.10
*/
void
gst_element_call_async (GstElement * element, GstElementCallAsyncFunc func,
gpointer user_data, GDestroyNotify destroy_notify)
{
GstElementCallAsyncData *async_data;
g_return_if_fail (GST_IS_ELEMENT (element));
async_data = g_new0 (GstElementCallAsyncData, 1);
async_data->element = gst_object_ref (element);
async_data->func = func;
async_data->user_data = user_data;
async_data->destroy_notify = destroy_notify;
g_thread_pool_push (gst_element_pool, async_data, NULL);
}
......@@ -816,6 +816,13 @@ GstStateChangeReturn gst_element_continue_state (GstElement * element,
GstStateChangeReturn ret);
void gst_element_lost_state (GstElement * element);
typedef void (*GstElementCallAsyncFunc) (GstElement * element,
gpointer user_data);
void gst_element_call_async (GstElement * element,
GstElementCallAsyncFunc func, gpointer user_data,
GDestroyNotify destroy_notify);
/* factory management */
GstElementFactory* gst_element_get_factory (GstElement *element);
......
......@@ -478,6 +478,7 @@ EXPORTS
gst_element_add_pad
gst_element_add_property_deep_notify_watch
gst_element_add_property_notify_watch
gst_element_call_async
gst_element_change_state
gst_element_class_add_metadata
gst_element_class_add_pad_template
......
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