jackdbus: Stop recurrent wakeups when no save is pending

Most processing happens as a result of an incoming
DBus event. The only case when a timed processing
is needed is due to an pending save.

Instead of implementing a full event loop just run the
timed loop while a save is pending, and use an
infinite timeout otherwise.

Fix for jackaudio/jack2#962

Thanks @StefanBruens

(cherry picked from commit fd1ac1422460c02cba17ea3053a4e6517290750c)

dbus/controller.c

@@ -720,15 +720,15 @@ jack_controller_destroy(
     free(controller_ptr);
 }
 
-void
+bool
 jack_controller_run(
     void * context)
 {
     struct sysinfo si;
 
     if (controller_ptr->pending_save == 0)
     {
-        return;
+        return false;
     }
 
     if (sysinfo(&si) != 0)
@@ -737,11 +737,12 @@ jack_controller_run(
     }
     else if (si.uptime < controller_ptr->pending_save + 2) /* delay save by two seconds */
     {
-        return;
+        return true;
     }
 
     controller_ptr->pending_save = 0;
     jack_controller_settings_save_auto(controller_ptr);
+    return false;
 }
 
 #undef controller_ptr

dbus/controller.h

@@ -20,11 +20,13 @@
 #ifndef CONTROLLER_H__2CC80B1E_8D5D_45E3_A9D8_9086DDF68BB5__INCLUDED
 #define CONTROLLER_H__2CC80B1E_8D5D_45E3_A9D8_9086DDF68BB5__INCLUDED
 
+#include <stdbool.h>
+
 void *
 jack_controller_create(
     DBusConnection *connection);
 
-void
+bool
 jack_controller_run(
     void *controller_ptr);
 

dbus/jackdbus.c

@@ -857,6 +857,7 @@ main (int argc, char **argv)
     void *controller_ptr;
     struct stat st;
     char timestamp_str[26];
+    bool save_pending;
 
     st.st_mtime = 0;
     stat(argv[0], &st);
@@ -954,9 +955,10 @@ main (int argc, char **argv)
     jack_info("Listening for D-Bus messages");
 
     g_exit_command = FALSE;
-    while (!g_exit_command && dbus_connection_read_write_dispatch (g_connection, 200))
+    save_pending = false;
+    while (!g_exit_command && dbus_connection_read_write_dispatch (g_connection, (save_pending ? 200 : -1)))
     {
-        jack_controller_run(controller_ptr);
+        save_pending = jack_controller_run(controller_ptr);
     }
 
     jack_controller_destroy(controller_ptr);