master: Send SIGQUIT to processes running at deinit to close socket listeners.

This allows Dovecot to be restarted even when some lmtp/doveadm process is
running for a long time. Otherwise it would keep the inet_listener socket
open and prevent the new Dovecot from binding to the port.

diff --git a/src/master/service-monitor.c b/src/master/service-monitor.c
index 761c6cbbeea44036e3ba28e3db63f79d9389c7bf..a74936f0142cc1b0697626925972f15850b68af3 100644 (file)
--- a/src/master/service-monitor.c
+++ b/src/master/service-monitor.c
@@ -597,6 +597,56 @@ static void services_monitor_wait(struct service_list *service_list)
        }
 }
 
+static bool service_processes_close_listeners(struct service *service)
+{
+       struct service_process *process = service->processes;
+       bool ret = FALSE;
+
+       for (; process != NULL; process = process->next) {
+               if (kill(process->pid, SIGQUIT) == 0)
+                       ret = TRUE;
+               else if (errno != ESRCH) {
+                       service_error(service, "kill(%s, SIGQUIT) failed: %m",
+                                     dec2str(process->pid));
+               }
+       }
+       return ret;
+}
+
+static bool
+service_list_processes_close_listeners(struct service_list *service_list)
+{
+       struct service *const *servicep;
+       bool ret = FALSE;
+
+       array_foreach(&service_list->services, servicep) {
+               if (service_processes_close_listeners(*servicep))
+                       ret = TRUE;
+       }
+       return ret;
+}
+
+static void services_monitor_wait_and_kill(struct service_list *service_list)
+{
+       /* we've notified all children that the master is dead.
+          now wait for the children to either die or to tell that
+          they're no longer listening for new connections. */
+       services_monitor_wait(service_list);
+
+       /* Even if the waiting stopped early because all the process_avail==0,
+          it can mean that there are processes that have the listener socket
+          open (just not actively being listened to). We'll need to make sure
+          that those sockets are closed before we exit, so that a restart
+          won't fail. Do this by sending SIGQUIT to all the child processes
+          that are left, which are handled by lib-master to immediately close
+          the listener in the signal handler itself. */
+       if (service_list_processes_close_listeners(service_list)) {
+               /* SIGQUITs were sent. wait a little bit to make sure they're
+                  also processed before quitting. */
+               usleep(100000);
+       }
+}
+
 void services_monitor_stop(struct service_list *service_list, bool wait)
 {
        struct service *const *services;
@@ -604,12 +654,8 @@ void services_monitor_stop(struct service_list *service_list, bool wait)
        array_foreach(&service_list->services, services)
                service_monitor_close_dead_pipe(*services);
 
-       if (wait) {
-               /* we've notified all children that the master is dead.
-                  now wait for the children to either die or to tell that
-                  they're no longer listening for new connections */
-               services_monitor_wait(service_list);
-       }
+       if (wait)
+               services_monitor_wait_and_kill(service_list);
 
        if (service_list->io_master != NULL)
                io_remove(&service_list->io_master);