logind: handle closing sessions over daemon restarts

It may happen that you have several sessions with the same VT:

 - Open a session c1 which leaves some processes around, and log out. The
   session will stay in State=closing and become Active=no.
 - Log back in on the same VT, get a new session "c2" which is State=active and
   Active=yes.

When restarting logind after that, the first session that matches the current
VT becomes Active=yes, which will be c1; c2 thus is Active=no and does not get
the usual polkit/device ACL privileges.

Restore the "closing" state in session_load(), to avoid treating all restored
sessions as State=active. In seat_active_vt_changed(), prefer active sessions
over closing ones if more than one session matches the current VT.

Finally, fix the confusing comment in session_load() and explain it a bit
better.

https://launchpad.net/bugs/1415104

1 files changed, 13 insertions, 1 deletions

diff --git a/src/login/logind-seat.c b/src/login/logind-seat.c
index 197138c4e..126c5b84c 100644
--- a/src/login/logind-seat.c
+++ b/src/login/logind-seat.c
@@ -340,12 +340,24 @@ int seat_active_vt_changed(Seat *s, unsigned int vtnr) {
 
         log_debug("VT changed to %u", vtnr);
 
+        /* we might have earlier closing sessions on the same VT, so try to
+         * find a running one first */
         LIST_FOREACH(sessions_by_seat, i, s->sessions)
-                if (i->vtnr == vtnr) {
+                if (i->vtnr == vtnr && !i->stopping) {
                         new_active = i;
                         break;
                 }
 
+        if (!new_active) {
+                /* no running one? then we can't decide which one is the
+                 * active one, let the first one win */
+                LIST_FOREACH(sessions_by_seat, i, s->sessions)
+                        if (i->vtnr == vtnr) {
+                                new_active = i;
+                                break;
+                        }
+        }
+
         r = seat_set_active(s, new_active);
         manager_spawn_autovt(s->manager, vtnr);