res_stasis: Add control ref to playback and recording structs.

The stasis_app_playback and stasis_app_recording structs need to have a
struct stasis_app_control ref.  Other threads can get a reference to the
playback and recording structs from their respective global container.
These other threads can then use the control pointer they contain after
the control struct has gone.

* Add control ref to stasis_app_playback and stasis_app_recording structs.

With the refs added, the control command queue can now have a circular
control reference which will cause the control struct to never get
released if the control's command queue is not flushed when the channel
leaves the Stasis application.  Also the command queue needs better
protection from adding commands if the control->is_done flag is set.

* Flush the control command queue on exit.

ASTERISK-25882 #close

Change-Id: I3cf1fb59cbe6f50f20d9e35a2c07ac07d7f4320d

2 files changed, 38 insertions, 8 deletions

diff --git a/res/stasis/control.c b/res/stasis/control.c
index a1004248f..86f94423d 100644
--- a/res/stasis/control.c
+++ b/res/stasis/control.c
@@ -251,6 +251,11 @@ static struct stasis_app_command *exec_command_on_condition(
 	}
 
 	ao2_lock(control->command_queue);
+	if (control->is_done) {
+		ao2_unlock(control->command_queue);
+		ao2_ref(command, -1);
+		return NULL;
+	}
 	if (can_exec_fn && (retval = can_exec_fn(control))) {
 		ao2_unlock(control->command_queue);
 		command_complete(command, retval);
@@ -402,7 +407,10 @@ int control_is_done(struct stasis_app_control *control)
 
 void control_mark_done(struct stasis_app_control *control)
 {
+	/* Locking necessary to sync with other threads adding commands to the queue. */
+	ao2_lock(control->command_queue);
 	control->is_done = 1;
+	ao2_unlock(control->command_queue);
 }
 
 struct stasis_app_control_continue_data {
@@ -427,7 +435,7 @@ static int app_control_continue(struct stasis_app_control *control,
 	/* Called from stasis_app_exec thread; no lock needed */
 	ast_explicit_goto(control->channel, continue_data->context, continue_data->extension, continue_data->priority);
 
-	control->is_done = 1;
+	control_mark_done(control);
 
 	return 0;
 }
@@ -1115,24 +1123,36 @@ int stasis_app_control_queue_control(struct stasis_app_control *control,
 	return ast_queue_control(control->channel, frame_type);
 }
 
+void control_flush_queue(struct stasis_app_control *control)
+{
+	struct ao2_iterator iter;
+	struct stasis_app_command *command;
+
+	iter = ao2_iterator_init(control->command_queue, AO2_ITERATOR_UNLINK);
+	while ((command = ao2_iterator_next(&iter))) {
+		command_complete(command, -1);
+		ao2_ref(command, -1);
+	}
+	ao2_iterator_destroy(&iter);
+}
+
 int control_dispatch_all(struct stasis_app_control *control,
 	struct ast_channel *chan)
 {
 	int count = 0;
-	struct ao2_iterator i;
-	void *obj;
+	struct ao2_iterator iter;
+	struct stasis_app_command *command;
 
 	ast_assert(control->channel == chan);
 
-	i = ao2_iterator_init(control->command_queue, AO2_ITERATOR_UNLINK);
-
-	while ((obj = ao2_iterator_next(&i))) {
-		RAII_VAR(struct stasis_app_command *, command, obj, ao2_cleanup);
+	iter = ao2_iterator_init(control->command_queue, AO2_ITERATOR_UNLINK);
+	while ((command = ao2_iterator_next(&iter))) {
 		command_invoke(command, control, chan);
+		ao2_ref(command, -1);
 		++count;
 	}
+	ao2_iterator_destroy(&iter);
 
-	ao2_iterator_destroy(&i);
 	return count;
 }
 
diff --git a/res/stasis/control.h b/res/stasis/control.h
index d053a35f7..1d37a494a 100644
--- a/res/stasis/control.h
+++ b/res/stasis/control.h
@@ -41,6 +41,16 @@
 struct stasis_app_control *control_create(struct ast_channel *channel, struct stasis_app *app);
 
 /*!
+ * \brief Flush the control command queue.
+ * \since 13.9.0
+ *
+ * \param control Control object to flush command queue.
+ *
+ * \return Nothing
+ */
+void control_flush_queue(struct stasis_app_control *control);
+
+/*!
  * \brief Dispatch all commands enqueued to this control.
  *
  * \param control Control object to dispatch.