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, 2 insertions, 0 deletions

diff --git a/src/machine/machine.h b/src/machine/machine.h
index b1cd26662f..0132b65a97 100644
--- a/src/machine/machine.h
+++ b/src/machine/machine.h
@@ -82,6 +82,7 @@ struct Machine {
 
         bool in_gc_queue:1;
         bool started:1;
+        bool stopping:1;
 
         sd_bus_message *create_message;
 
@@ -100,6 +101,7 @@ bool machine_check_gc(Machine *m, bool drop_not_started);
 void machine_add_to_gc_queue(Machine *m);
 int machine_start(Machine *m, sd_bus_message *properties, sd_bus_error *error);
 int machine_stop(Machine *m);
+int machine_finalize(Machine *m);
 int machine_save(Machine *m);
 int machine_load(Machine *m);
 int machine_kill(Machine *m, KillWho who, int signo);