machined: rework state tracking logic for machines

This splits up the stopping logic for machines into two steps: first on
machine_stop() we begin with the shutdown of a machine by queuing the
stop method call for it. Then, in machine_finalize() we actually remove
the rest of its runtime context. This mimics closely how sessions are
handled in logind.

This also reworks the GC logic to strictly check the current state of
the machine unit, rather than shortcutting a few cases, like for example
assuming that UnitRemoved really means a machine is gone (which it isn't
since Reloading might trigger it, see #376).

Fixes #376.

1 files changed, 9 insertions, 1 deletions

diff --git a/src/machine/machined.c b/src/machine/machined.c
index 9bfe2add54..1eeeaf17a5 100644
--- a/src/machine/machined.c
+++ b/src/machine/machined.c
@@ -247,8 +247,16 @@ void manager_gc(Manager *m, bool drop_not_started) {
                 LIST_REMOVE(gc_queue, m->machine_gc_queue, machine);
                 machine->in_gc_queue = false;
 
-                if (!machine_check_gc(machine, drop_not_started)) {
+                /* First, if we are not closing yet, initiate stopping */
+                if (!machine_check_gc(machine, drop_not_started) &&
+                    machine_get_state(machine) != MACHINE_CLOSING)
                         machine_stop(machine);
+
+                /* Now, the stop stop probably made this referenced
+                 * again, but if it didn't, then it's time to let it
+                 * go entirely. */
+                if (!machine_check_gc(machine, drop_not_started)) {
+                        machine_finalize(machine);
                         machine_free(machine);
                 }
         }