init: generate a state report when children exit

Whenever a childs is terminated the exit value is propagate through a
new state report. Thereby it becomes possibly for a managing component
to react upon the terminating condition of a child.

Issue #2558.

repos/os/src/init/child.cc

@@ -281,6 +281,9 @@ void Init::Child::report_state(Xml_generator &xml, Report_detail const &detail)
 		if (!_child.active())
 			xml.attribute("state", "incomplete");
 
+		if (_exited)
+			xml.attribute("exited", _exit_value);
+
 		if (detail.child_ram() && _child.ram_session_cap().valid()) {
 			xml.node("ram", [&] () {
 

repos/os/src/init/child.h

@@ -404,6 +404,14 @@ class Init::Child : Child_policy, Routed_service::Wakeup
 				               name, *this);
 		}
 
+		/*
+		 * Exit state of the child set when 'exit()' is executed
+		 * and reported afterwards through the state report.
+		 */
+
+		bool _exited     { false };
+		int  _exit_value { -1 };
+
 	public:
 
 		/**
@@ -535,6 +543,14 @@ class Init::Child : Child_policy, Routed_service::Wakeup
 				}
 			} catch (...) { }
 
+			/*
+			 * Trigger a new report for exited children so that any management
+			 * component may react upon it.
+			 */
+			_exited     = true;
+			_exit_value = exit_value;
+			_report_update_trigger.trigger_report_update();
+
 			/*
 			 * Print a message as the exit is not handled otherwise. There are
 			 * a number of automated tests that rely on this message. It is