context: add freeze/thaw recalc

Some operations like deactivating nodes deactivates all links to the
node and this causes a graph recalc for each link.

It's actually a bit more problematic with suspend, which first
deactivates the links and then suspends the ports. The suspension of the
ports cause a recalc, which for the not yet suspended ports makes the
link active again, causing issues then when the port is suspended later.

Make recalc a counter and only recalc when the counter is 0. If the
counter is not 0, set the pending recalc, which will trigger when the
counter goes to 0.

With this, we can add a freeze/thaw operation on the recalc and delay
recalculation until all ports and links are handled.

We can also group some other operations with a freeze/thaw pair, such as
the destruction of ports, which destroys all links. Also the destruction
of nodes can freeze the recalc until all ports are destroyed.

src/pipewire/context.c

@@ -56,7 +56,7 @@ struct impl {
 	struct pw_context this;
 	struct spa_handle *dbus_handle;
 	struct spa_plugin_loader plugin_loader;
-	unsigned int recalc:1;
+	int recalc;
 	unsigned int recalc_pending:1;
 
 	uint32_t cpu_count;
@@ -991,24 +991,40 @@ int pw_context_recalc_graph(struct pw_context *context, const char *reason)
 
 	pw_log_info("%p: busy:%d reason:%s", context, impl->recalc, reason);
 
-	if (impl->recalc) {
+	if (impl->recalc > 0) {
 		impl->recalc_pending = true;
 		return -EBUSY;
 	}
 
 again:
-	impl->recalc = true;
+	impl->recalc++;
 
 	pw_context_emit_recalc_graph(context);
 
-	impl->recalc = false;
-	if (impl->recalc_pending) {
+	if (--impl->recalc == 0 && impl->recalc_pending) {
 		impl->recalc_pending = false;
 		goto again;
 	}
 	return 0;
 }
 
+int pw_context_freeze_recalc_graph(struct pw_context *context)
+{
+	struct impl *impl = SPA_CONTAINER_OF(context, struct impl, this);
+	impl->recalc++;
+	return 0;
+}
+
+int pw_context_thaw_recalc_graph(struct pw_context *context, const char *reason)
+{
+	struct impl *impl = SPA_CONTAINER_OF(context, struct impl, this);
+	if (--impl->recalc == 0 && impl->recalc_pending) {
+		impl->recalc_pending = false;
+		pw_context_recalc_graph(context, reason);
+	}
+	return 0;
+}
+
 SPA_EXPORT
 int pw_context_add_spa_lib(struct pw_context *context,
 		const char *factory_regexp, const char *lib)

src/pipewire/impl-node.c

@@ -288,6 +288,8 @@ static void node_deactivate(struct pw_impl_node *this)
 	/* make sure the node doesn't get woken up while not active */
 	remove_node_from_graph(this);
 
+	pw_context_freeze_recalc_graph(this->context);
+
 	spa_list_for_each(port, &this->input_ports, link) {
 		spa_list_for_each(link, &port->links, input_link)
 			pw_impl_link_deactivate(link);
@@ -296,6 +298,7 @@ static void node_deactivate(struct pw_impl_node *this)
 		spa_list_for_each(link, &port->links, output_link)
 			pw_impl_link_deactivate(link);
 	}
+	pw_context_thaw_recalc_graph(this->context, "node deactivate");
 }
 
 static int idle_node(struct pw_impl_node *this)
@@ -329,6 +332,8 @@ static void node_activate(struct pw_impl_node *this)
 	struct pw_impl_port *port;
 
 	pw_log_debug("%p: activate", this);
+	pw_context_freeze_recalc_graph(this->context);
+
 	spa_list_for_each(port, &this->output_ports, link) {
 		struct pw_impl_link *link;
 		spa_list_for_each(link, &port->links, output_link)
@@ -339,6 +344,7 @@ static void node_activate(struct pw_impl_node *this)
 		spa_list_for_each(link, &port->links, input_link)
 			pw_impl_link_activate(link);
 	}
+	pw_context_thaw_recalc_graph(this->context, "node activate");
 }
 
 static int start_node(struct pw_impl_node *this)
@@ -541,6 +547,8 @@ static int suspend_node(struct pw_impl_node *this)
 	    (this->info.state == PW_NODE_STATE_SUSPENDED && impl->pending_state == PW_NODE_STATE_SUSPENDED))
 		return 0;
 
+	pw_context_freeze_recalc_graph(this->context);
+
 	node_deactivate(this);
 
 	pw_log_debug("%p: suspend node driving:%d driver:%d prepared:%d", this,
@@ -559,6 +567,8 @@ static int suspend_node(struct pw_impl_node *this)
 	spa_list_for_each(p, &this->output_ports, link)
 		pw_impl_port_suspend(p);
 
+	pw_context_thaw_recalc_graph(this->context, "node suspend");
+
 	node_update_state(this, PW_NODE_STATE_SUSPENDED, 0, NULL);
 
 	return res;
@@ -2408,15 +2418,15 @@ void pw_impl_node_destroy(struct pw_impl_node *node)
 	struct pw_impl_port *port;
 	struct pw_impl_node *follower;
 	struct pw_context *context = node->context;
-	bool active, had_driver;
 
-	active = node->active;
 	node->active = false;
 	node->runnable = false;
 
 	pw_log_debug("%p: destroy", impl);
 	pw_log_info("(%s-%u) destroy", node->name, node->info.id);
 
+	pw_context_freeze_recalc_graph(context);
+
 	node_deactivate(node);
 
 	suspend_node(node);
@@ -2424,7 +2434,6 @@ void pw_impl_node_destroy(struct pw_impl_node *node)
 	pw_impl_node_emit_destroy(node);
 
 	pw_log_debug("%p: driver node %p", impl, node->driver_node);
-	had_driver = node != node->driver_node;
 
 	/* remove ourself as a follower from the driver node */
 	spa_list_remove(&node->follower_link);
@@ -2458,10 +2467,7 @@ void pw_impl_node_destroy(struct pw_impl_node *node)
 		spa_hook_remove(&node->global_listener);
 		pw_global_destroy(node->global);
 	}
-
-	if (active || had_driver)
-		pw_context_recalc_graph(context,
-				"active node destroy");
+	pw_context_thaw_recalc_graph(context, "node destroy");
 
 	pw_log_debug("%p: free", node);
 	pw_impl_node_emit_free(node);

src/pipewire/impl-port.c

@@ -1515,7 +1515,10 @@ static int do_destroy_link(void *data, struct pw_impl_link *link)
 
 void pw_impl_port_unlink(struct pw_impl_port *port)
 {
+	struct pw_context *context = port->node->context;
+	pw_context_freeze_recalc_graph(context);
 	pw_impl_port_for_each_link(port, do_destroy_link, port);
+	pw_context_thaw_recalc_graph(context, "port unlink");
 }
 
 static int do_remove_port(struct spa_loop *loop,

src/pipewire/private.h

@@ -1306,6 +1306,8 @@ int pw_proxy_init(struct pw_proxy *proxy, struct pw_core *core, const char *type
 void pw_proxy_remove(struct pw_proxy *proxy);
 
 int pw_context_recalc_graph(struct pw_context *context, const char *reason);
+int pw_context_freeze_recalc_graph(struct pw_context *context);
+int pw_context_thaw_recalc_graph(struct pw_context *context, const char *reason);
 
 void pw_impl_port_update_info(struct pw_impl_port *port, const struct spa_port_info *info);