Add service configuration reloading

This commit add the ability to initd to reload the service configuration
while running. The new configuration is merged with the existing one as
follows:

For each target:
 - If the existing service list is not NULL, we have not started that
   target yet. Simply replace it with the new list.
 - If it is NULL, the services have already been started.
    - First, remove all entries for services in that target that no
      loner exist (except from the 'running' list).
    - Second, add new services that we don't have yet. Treat them as
      recently diseased and let the user start them manualy.

Signed-off-by: David Oberhollenzer <goliath@infraroot.at>

cmd/service/disable.c

@@ -4,6 +4,7 @@
 #include <stdlib.h>
 #include <unistd.h>
 #include <string.h>
+#include <signal.h>
 #include <stdio.h>
 #include <errno.h>
 
@@ -55,6 +56,8 @@ static int cmd_disable(int argc, char **argv)
 		goto out;
 	}
 
+	kill(1, SIGHUP);
+
 	ret = EXIT_SUCCESS;
 out:
 	free(linkname);

cmd/service/enable.c

@@ -4,6 +4,7 @@
 #include <stdlib.h>
 #include <unistd.h>
 #include <string.h>
+#include <signal.h>
 #include <stdio.h>
 #include <errno.h>
 
@@ -60,6 +61,8 @@ static int cmd_enable(int argc, char **argv)
 		goto out;
 	}
 
+	kill(1, SIGHUP);
+
 	ret = EXIT_SUCCESS;
 out:
 	free(linkname);

initd/init.h

@@ -68,6 +68,8 @@ void supervisor_init(void);
 
 bool supervisor_process_queues(void);
 
+void supervisor_reload_config(void);
+
 void supervisor_answer_status_request(int fd, const void *dest_addr,
 				      size_t addrlen, E_SERVICE_STATE filter);
 

initd/main.c

@@ -30,6 +30,9 @@ static void handle_signal(void)
 	case SIGINT:
 		supervisor_set_target(TGT_REBOOT);
 		break;
+	case SIGHUP:
+		supervisor_reload_config();
+		break;
 	case SIGUSR1:
 		if (sockfd >= 0) {
 			close(sockfd);

initd/signal_linux.c

@@ -19,6 +19,7 @@ int sigsetup(void)
 	sigaddset(&mask, SIGINT);
 	sigaddset(&mask, SIGTERM);
 	sigaddset(&mask, SIGUSR1);
+	sigaddset(&mask, SIGHUP);
 
 	sfd = signalfd(-1, &mask, SFD_CLOEXEC);
 	if (sfd == -1) {

initd/supervisor.c

@@ -13,6 +13,46 @@ static service_t *failed = NULL;
 static int singleshot = 0;
 static bool waiting = false;
 
+static bool find_service(service_t *list, service_t *svc)
+{
+	while (list != NULL) {
+		if (strcmp(list->fname, svc->fname) == 0)
+			return true;
+
+		list = list->next;
+	}
+	return false;
+}
+
+static void remove_not_in_list(service_t **current, service_t *list, int tgt)
+{
+	service_t *it = *current, *prev = NULL;
+
+	while (it != NULL) {
+		if (it->target == tgt && !find_service(list, it)) {
+			if (prev == NULL) {
+				delsvc(it);
+				*current = (*current)->next;
+				it = *current;
+			} else {
+				prev->next = it->next;
+				delsvc(it);
+				it = prev->next;
+			}
+		} else {
+			prev = it;
+			it = it->next;
+		}
+	}
+}
+
+static bool have_service(service_t *svc)
+{
+	return find_service(running, svc) || find_service(terminated, svc) ||
+		find_service(queue, svc) || find_service(completed, svc) ||
+		find_service(failed, svc);
+}
+
 static int start_service(service_t *svc)
 {
 	if (svc->id < 1)
@@ -145,6 +185,45 @@ void supervisor_init(void)
 	print_status("reading configuration from " SVCDIR, status, false);
 }
 
+void supervisor_reload_config(void)
+{
+	service_list_t newcfg;
+	service_t *svc;
+	int i;
+
+	if (svcscan(SVCDIR, &newcfg, RDSVC_NO_EXEC | RDSVC_NO_CTTY))
+		return;
+
+	for (i = 0; i < TGT_MAX; ++i) {
+		if (cfg.targets[i] == NULL) {
+			remove_not_in_list(&queue, newcfg.targets[i], i);
+			remove_not_in_list(&terminated, newcfg.targets[i], i);
+			remove_not_in_list(&completed, newcfg.targets[i], i);
+			remove_not_in_list(&failed, newcfg.targets[i], i);
+
+			while (newcfg.targets[i] != NULL) {
+				svc = newcfg.targets[i];
+				newcfg.targets[i] = svc->next;
+
+				if (have_service(svc)) {
+					delsvc(svc);
+				} else {
+					svc->id = service_id++;
+					svc->status = EXIT_SUCCESS;
+					svc->next = completed;
+					completed = svc;
+				}
+			}
+		} else {
+			svc = cfg.targets[i];
+			cfg.targets[i] = newcfg.targets[i];
+			newcfg.targets[i] = svc;
+		}
+	}
+
+	del_svc_list(&newcfg);
+}
+
 bool supervisor_process_queues(void)
 {
 	service_t *svc;