init: apply changes of <provides> nodes

This patch enables init to apply changes of any server's <provides>
declarations in a differential way. Servers can in principle be extended
by new services without re-starting them. Of course, changes of the
<provides> declarations may affect clients or would-be clients as this
information is taken into account for the session routing.

repos/os/include/init/child.h

@@ -658,6 +658,49 @@ class Init::Child : Child_policy, Child_service::Wakeup
 			catch (Parent::Service_denied) { return false; }
 		}
 
+		static Xml_node _provides_sub_node(Xml_node start_node)
+		{
+			return start_node.has_sub_node("provides")
+			     ? start_node.sub_node("provides") : Xml_node("<provides/>");
+		}
+
+		/**
+		 * Return true if service is provided by this child
+		 */
+		bool _provided_by_this(Routed_service const &service)
+		{
+			return service.has_id_space(_session_requester.id_space());
+		}
+
+		/**
+		 * Return true if service of specified <provides> sub node is known
+		 */
+		bool _service_exists(Xml_node node) const
+		{
+			bool exists = false;
+			_child_services.for_each([&] (Routed_service const &service) {
+				if (_provided_by_this(service) &&
+				    service.name() == node.attribute_value("name", Service::Name()))
+					exists = true; });
+
+			return exists;
+		}
+
+		void _add_service(Xml_node service)
+		{
+			Service::Name const name =
+				service.attribute_value("name", Service::Name());
+
+			if (_verbose.enabled())
+				log("  provides service ", name);
+
+			new (_alloc)
+				Routed_service(_child_services, this->name(), _ram_accessor,
+				               _session_requester.id_space(),
+				               _child.session_factory(),
+				               name, *this);
+		}
+
 	public:
 
 		/**
@@ -719,25 +762,9 @@ class Init::Child : Child_policy, Child_service::Wakeup
 			/*
 			 * Determine services provided by the child
 			 */
-			try {
+			_provides_sub_node(start_node)
-				Xml_node service_node = start_node.sub_node("provides").sub_node("service");
+				.for_each_sub_node("service",
-
+				                   [&] (Xml_node node) { _add_service(node); });
-				for (; ; service_node = service_node.next("service")) {
-
-					char name[Service::Name::capacity()];
-					service_node.attribute("name").value(name, sizeof(name));
-
-					if (_verbose.enabled())
-						log("  provides service ", Cstring(name));
-
-					new (_alloc)
-						Routed_service(child_services, this->name(), _ram_accessor,
-						               _session_requester.id_space(),
-						               _child.session_factory(),
-						               name, *this);
-				}
-			}
-			catch (Xml_node::Nonexistent_sub_node) { }
 
 			/*
 			 * Construct inline config ROM service if "config" node is present.
@@ -812,6 +839,17 @@ class Init::Child : Child_policy, Child_service::Wakeup
 			if (_state == STATE_ABANDONED)
 				return NO_SIDE_EFFECTS;
 
+			/*
+			 * If the child's environment is incomplete, restart it to attempt
+			 * the re-routing of its environment sessions.
+			 */
+			if (!_child.active()) {
+				abandon();
+				return MAY_HAVE_SIDE_EFFECTS;
+			}
+
+			bool provided_services_changed = false;
+
 			enum Config_update { CONFIG_APPEARED, CONFIG_VANISHED,
 			                     CONFIG_CHANGED,  CONFIG_UNCHANGED };
 
@@ -856,6 +894,41 @@ class Init::Child : Child_policy, Child_service::Wakeup
 						config_update = CONFIG_CHANGED;
 				}
 
+				/*
+				 * Import updated <provides> node
+				 *
+				 * First abandon services that are no longer present in the
+				 * <provides> node. Then add services that have newly appeared.
+				 */
+				_child_services.for_each([&] (Routed_service &service) {
+
+					if (!_provided_by_this(service))
+						return;
+
+					typedef Service::Name Name;
+					Name const name = service.name();
+
+					bool still_provided = false;
+					_provides_sub_node(start_node)
+						.for_each_sub_node("service", [&] (Xml_node node) {
+							if (name == node.attribute_value("name", Name()))
+								still_provided = true; });
+
+					if (!still_provided) {
+						service.abandon();
+						provided_services_changed = true;
+					}
+				});
+
+				_provides_sub_node(start_node).for_each_sub_node("service",
+				                                                 [&] (Xml_node node) {
+					if (_service_exists(node))
+						return;
+
+					_add_service(node);
+					provided_services_changed = true;
+				});
+
 				/*
 				 * Import new binary name. A change may affect the route for
 				 * the binary's ROM session, triggering the restart of the
@@ -892,6 +965,10 @@ class Init::Child : Child_policy, Child_service::Wakeup
 					return MAY_HAVE_SIDE_EFFECTS;
 				}
 			}
+
+			if (provided_services_changed)
+				return MAY_HAVE_SIDE_EFFECTS;
+
 			return NO_SIDE_EFFECTS;
 		}
 
@@ -908,6 +985,9 @@ class Init::Child : Child_policy, Child_service::Wakeup
 				if (detail.ids())
 					xml.attribute("id", _id.value);
 
+				if (!_child.active())
+					xml.attribute("state", "incomplete");
+
 				if (detail.child_ram() && _child.ram_session_cap().valid()) {
 					xml.node("ram", [&] () {
 						/*

repos/os/run/init.run

@@ -200,6 +200,111 @@ append config {
 			<sleep ms="100"/>
 
 
+			<message string="test changing provided services"/>
+
+			<!-- Initially, the log service lacks the <provides> declaration.
+			     Therefore the attempt to route the LOG session of the client
+			     to the 'log' fails. The environment of 'dummy' will remain
+			     incomplete. -->
+
+			<init_config>
+				<report requested="yes"/>
+				<parent-provides>
+					<service name="ROM"/> <service name="RAM"/>
+					<service name="CPU"/> <service name="PD"/>
+					<service name="LOG"/>
+				</parent-provides>
+				<start name="log">
+					<binary name="dummy"/>
+					<resource name="RAM" quantum="1M"/>
+					<config/>
+					<route> <any-service> <parent/> </any-service> </route>
+				</start>
+				<start name="dummy">
+					<resource name="RAM" quantum="1M"/>
+					<config> <log string="started"/> </config>
+					<route>
+						<service name="LOG"> <child name="log"/> </service>
+						<any-service> <parent/> </any-service>
+					</route>
+				</start>
+			</init_config>
+			<sleep ms="200"/>
+			<expect_init_state>
+				<node name="child"> <attribute name="name" value="log"/> </node>
+				<node name="child">
+					<attribute name="name"  value="dummy"/>
+					<attribute name="state" value="incomplete"/>
+				</node>
+			</expect_init_state>
+
+			<!-- We add the <provides> node to the log server and thereby
+			     make the LOG route of the 'dummy' client available. The
+			     server is expected to remain unaffected but the client should
+			     be restarted to re-route its LOG session to the server -->
+
+			<init_config>
+				<parent-provides>
+					<service name="ROM"/> <service name="RAM"/>
+					<service name="CPU"/> <service name="PD"/>
+					<service name="LOG"/>
+				</parent-provides>
+				<start name="log">
+					<binary name="dummy"/>
+					<resource name="RAM" quantum="1M"/>
+					<provides> <service name="LOG"/> </provides>
+					<config version="providing service"> <log_service/> </config>
+					<route> <any-service> <parent/> </any-service> </route>
+				</start>
+				<start name="dummy">
+					<resource name="RAM" quantum="1M"/>
+					<config> <log string="started"/> </config>
+					<route>
+						<service name="LOG"> <child name="log"/> </service>
+						<any-service> <parent/> </any-service>
+					</route>
+				</start>
+			</init_config>
+			<expect_log string="[init -> log] config 2: providing service"/>
+			<expect_log string="[init -> log] [dummy] started"/>
+
+			<!-- We remove <provides> node from 'log' service and thereby
+			     make the LOG service unavailble for 'dummy'. Consequently,
+			     'dummy' will be restarted but will ultimately remain
+			     incomplete (as the LOG environment session cannot be routed).
+			     The server stays alive and reports its third config. -->
+
+			<init_config>
+				<report requested="yes"/>
+				<parent-provides>
+					<service name="ROM"/> <service name="RAM"/>
+					<service name="CPU"/> <service name="PD"/>
+					<service name="LOG"/>
+				</parent-provides>
+				<start name="log">
+					<binary name="dummy"/>
+					<resource name="RAM" quantum="1M"/>
+					<config version="became unavailable"/>
+					<route> <any-service> <parent/> </any-service> </route>
+				</start>
+				<start name="dummy">
+					<resource name="RAM" quantum="1M"/>
+					<config> <log string="started"/> </config>
+					<route>
+						<service name="LOG"> <child name="log"/> </service>
+						<any-service> <parent/> </any-service>
+					</route>
+				</start>
+			</init_config>
+			<sleep ms="150"/>
+			<expect_init_state>
+				<node name="child">
+					<attribute name="name"  value="dummy"/>
+					<attribute name="state" value="incomplete"/>
+				</node>
+			</expect_init_state>
+
+
 			<message string="update child config"/>
 
 			<init_config>

repos/os/src/test/init/main.cc

@@ -178,6 +178,8 @@ struct Test::Main : Log_message_handler
 
 	Timer::Connection _timer { _env };
 
+	bool _timer_scheduled = false;
+
 	Reporter _init_config_reporter { _env, "config",  "init.config" };
 
 	Attached_rom_dataspace _config { _env, "config" };
@@ -269,8 +271,11 @@ struct Test::Main : Log_message_handler
 			}
 
 			if (step.type() == "sleep") {
-				unsigned long const timeout_ms = step.attribute_value("ms", 250UL);
+				if (!_timer_scheduled) {
-				_timer.trigger_once(timeout_ms*1000);
+					unsigned long const timeout_ms = step.attribute_value("ms", 250UL);
+					_timer.trigger_once(timeout_ms*1000);
+					_timer_scheduled = true;
+				}
 				return;
 			}
 
@@ -311,6 +316,8 @@ struct Test::Main : Log_message_handler
 			throw Exception();
 		}
 
+		_timer_scheduled = false;
+
 		_advance_step();
 		_execute_curr_step();
 	}