core: when restarting services, don't close fds

We would close all the stored fds in service_release_resources(), which of
course broke the whole concept of storing fds over service restart.

Fixes #4408.

src/core/service.c

@@ -289,7 +289,17 @@ static void service_fd_store_unlink(ServiceFDStore *fs) {
         free(fs);
 }
 
-static void service_release_resources(Unit *u) {
+static void service_release_fd_store(Service *s) {
+        assert(s);
+
+        log_unit_debug(UNIT(s), "Releasing all stored fds");
+        while (s->fd_store)
+                service_fd_store_unlink(s->fd_store);
+
+        assert(s->n_fd_store == 0);
+}
+
+static void service_release_resources(Unit *u, bool inactive) {
         Service *s = SERVICE(u);
 
         assert(s);
@@ -297,16 +307,14 @@ static void service_release_resources(Unit *u) {
         if (!s->fd_store && s->stdin_fd < 0 && s->stdout_fd < 0 && s->stderr_fd < 0)
                 return;
 
-        log_unit_debug(u, "Releasing all resources.");
+        log_unit_debug(u, "Releasing resources.");
 
         s->stdin_fd = safe_close(s->stdin_fd);
         s->stdout_fd = safe_close(s->stdout_fd);
         s->stderr_fd = safe_close(s->stderr_fd);
 
-        while (s->fd_store)
-                service_fd_store_unlink(s->fd_store);
-
-        assert(s->n_fd_store == 0);
+        if (inactive)
+                service_release_fd_store(s);
 }
 
 static void service_done(Unit *u) {
@@ -350,7 +358,7 @@ static void service_done(Unit *u) {
 
         s->timer_event_source = sd_event_source_unref(s->timer_event_source);
 
-        service_release_resources(u);
+        service_release_resources(u, true);
 }
 
 static int on_fd_store_io(sd_event_source *e, int fd, uint32_t revents, void *userdata) {

src/core/unit.c

@@ -302,6 +302,7 @@ int unit_set_description(Unit *u, const char *description) {
 
 bool unit_check_gc(Unit *u) {
         UnitActiveState state;
+        bool inactive;
         assert(u);
 
         if (u->job)
@@ -311,16 +312,17 @@ bool unit_check_gc(Unit *u) {
                 return true;
 
         state = unit_active_state(u);
+        inactive = state == UNIT_INACTIVE;
 
         /* If the unit is inactive and failed and no job is queued for
          * it, then release its runtime resources */
         if (UNIT_IS_INACTIVE_OR_FAILED(state) &&
             UNIT_VTABLE(u)->release_resources)
-                UNIT_VTABLE(u)->release_resources(u);
+                UNIT_VTABLE(u)->release_resources(u, inactive);
 
         /* But we keep the unit object around for longer when it is
          * referenced or configured to not be gc'ed */
-        if (state != UNIT_INACTIVE)
+        if (!inactive)
                 return true;
 
         if (u->no_gc)

src/core/unit.h

@@ -372,7 +372,7 @@ struct UnitVTable {
 
         /* When the unit is not running and no job for it queued we
          * shall release its runtime resources */
-        void (*release_resources)(Unit *u);
+        void (*release_resources)(Unit *u, bool inactive);
 
         /* Invoked on every child that died */
         void (*sigchld_event)(Unit *u, pid_t pid, int code, int status);