From aa6c8bcd17b37634fc7e4d5d59b6b9d93625b4a3 Mon Sep 17 00:00:00 2001
From: David Herrmann <dh.herrmann@gmail.com>
Date: Tue, 25 Feb 2014 13:08:24 +0100
Subject: [PATCH] login: set pos-slot to fallback on pos-eviction

If we evict a session position, we open the position slot for future
sessions. However, there might already be another session on the same
position if both were started on the same VT. This is currently done if
gdm spawns the session on its own Xserver.

Hence, look for such a session on pos-eviction and claim the new slot
immediately.

(cherry picked from commit 3e6b205f81e743c7354ccbc69eb45afbdbebe2dc)
---
 src/login/logind-seat.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/src/login/logind-seat.c b/src/login/logind-seat.c
index 36ec7ed..96cf08e 100644
--- a/src/login/logind-seat.c
+++ b/src/login/logind-seat.c
@@ -459,6 +459,7 @@ int seat_stop_sessions(Seat *s, bool force) {
 }
 
 void seat_evict_position(Seat *s, Session *session) {
+        Session *iter;
         unsigned int pos = session->pos;
 
         session->pos = 0;
@@ -466,8 +467,19 @@ void seat_evict_position(Seat *s, Session *session) {
         if (!pos)
                 return;
 
-        if (pos < s->position_count && s->positions[pos] == session)
+        if (pos < s->position_count && s->positions[pos] == session) {
                 s->positions[pos] = NULL;
+
+                /* There might be another session claiming the same
+                 * position (eg., during gdm->session transition), so lets look
+                 * for it and set it on the free slot. */
+                LIST_FOREACH(sessions_by_seat, iter, s->sessions) {
+                        if (iter->pos == pos) {
+                                s->positions[pos] = iter;
+                                break;
+                        }
+                }
+        }
 }
 
 void seat_claim_position(Seat *s, Session *session, unsigned int pos) {