core/slice: skip member units without realized cgroup during freeze or thaw

This ensures that services with `RemainAfterExit` but without any
process running won't cause failure during freeze.

diff --git a/src/core/slice.c b/src/core/slice.c
index c453aa033e7115bbeadea61c05e793226785abfe..4824a300d0718c4c45e4aa82d0467ff8cb5407aa 100644 (file)
--- a/src/core/slice.c
+++ b/src/core/slice.c
@@ -381,6 +381,9 @@ static int slice_freezer_action(Unit *s, FreezerAction action) {
         }
 
         UNIT_FOREACH_DEPENDENCY(member, s, UNIT_ATOM_SLICE_OF) {
+                if (!member->cgroup_realized)
+                        continue;
+
                 if (action == FREEZER_FREEZE)
                         r = UNIT_VTABLE(member)->freeze(member);
                 else