logind: rework session shutdown logic

Simplify the shutdown logic a bit:

- Keep the session FIFO around in the PAM module, even after the session
  shutdown hook has been finished. This allows logind to track precisely
  when the PAM handler goes away.

- In the ReleaseSession() call start a timer, that will stop terminate
  the session when elapsed.

- Never fiddle with the KillMode of scopes to configure whether user
  processes should be killed or not. Instead, simply leave the scope
  units around when we terminate a session whose processes should not be
  killed.

- When killing is enabled, stop the session scope on FIFO EOF or after
  the ReleaseSession() timeout. When killing is disabled, simply tell
  PID 1 to abandon the scope.

Because the scopes stay around and hence all processes are always member
of a scope, the system shutdown logic should be more robust, as the
scopes can be shutdown as part of the usual shutdown logic.

1 files changed, 2 insertions, 1 deletions

diff --git a/src/login/logind.h b/src/login/logind.h
index b84137c78b..c1a5b6a80f 100644
--- a/src/login/logind.h
+++ b/src/login/logind.h
@@ -162,9 +162,10 @@ int manager_send_changed(Manager *manager, const char *property, ...) _sentinel_
 
 int manager_dispatch_delayed(Manager *manager);
 
-int manager_start_scope(Manager *manager, const char *scope, pid_t pid, const char *slice, const char *description, const char *after, const char *kill_mode, sd_bus_error *error, char **job);
+int manager_start_scope(Manager *manager, const char *scope, pid_t pid, const char *slice, const char *description, const char *after, sd_bus_error *error, char **job);
 int manager_start_unit(Manager *manager, const char *unit, sd_bus_error *error, char **job);
 int manager_stop_unit(Manager *manager, const char *unit, sd_bus_error *error, char **job);
+int manager_abandon_scope(Manager *manager, const char *scope, sd_bus_error *error);
 int manager_kill_unit(Manager *manager, const char *unit, KillWho who, int signo, sd_bus_error *error);
 int manager_unit_is_active(Manager *manager, const char *unit);
 int manager_job_is_active(Manager *manager, const char *path);