From d868eb3ced19d0624aa8ce948ccc8d8523551e78 Mon Sep 17 00:00:00 2001
From: Ray Strode <rstrode@redhat.com>
Date: Tue, 14 Aug 2018 10:21:17 -0400
Subject: [PATCH] local-display-factory: ignore spurios SeatNew signal at start
 up

Sometimes during startup, logind will send a `SeatNew` signal for
seat0 after GDM has already called `ListSeats` and processed `seat0`.

That `SeatNew` signal leads to GDM calling `create_display` twice in
quick succession.

This commit changes GDM to avoid such double processing, by ignoring
the `create_display` requests for seats that already have a prepared
display ("prepared" means "starting up").

Closes: https://gitlab.gnome.org/GNOME/gdm/issues/410
---
 daemon/gdm-local-display-factory.c | 33 +++++++++++++++++++++++-------
 1 file changed, 26 insertions(+), 7 deletions(-)

diff --git a/daemon/gdm-local-display-factory.c b/daemon/gdm-local-display-factory.c
index 39f3e30a3..7ec998efa 100644
--- a/daemon/gdm-local-display-factory.c
+++ b/daemon/gdm-local-display-factory.c
@@ -348,107 +348,126 @@ on_display_status_changed (GdmDisplay             *display,
         case GDM_DISPLAY_MANAGED:
                 break;
         default:
                 g_assert_not_reached ();
                 break;
         }
 
         g_free (seat_id);
         g_free (session_type);
         g_free (session_class);
 }
 
 static gboolean
 lookup_by_seat_id (const char *id,
                    GdmDisplay *display,
                    gpointer    user_data)
 {
         const char *looking_for = user_data;
         char *current;
         gboolean res;
 
         g_object_get (G_OBJECT (display), "seat-id", &current, NULL);
 
         res = g_strcmp0 (current, looking_for) == 0;
 
         g_free(current);
 
         return res;
 }
 
+static gboolean
+lookup_prepared_display_by_seat_id (const char *id,
+                                    GdmDisplay *display,
+                                    gpointer    user_data)
+{
+        int status;
+
+        status = gdm_display_get_status (display);
+
+        if (status != GDM_DISPLAY_PREPARED)
+                return FALSE;
+
+        return lookup_by_seat_id (id, display, user_data);
+}
+
 static GdmDisplay *
 create_display (GdmLocalDisplayFactory *factory,
                 const char             *seat_id,
                 const char             *session_type,
                 gboolean                initial)
 {
         GdmDisplayStore *store;
         GdmDisplay      *display = NULL;
         char            *active_session_id = NULL;
         int              ret;
 
         g_debug ("GdmLocalDisplayFactory: %s login display for seat %s requested",
                  session_type? : "X11", seat_id);
         store = gdm_display_factory_get_display_store (GDM_DISPLAY_FACTORY (factory));
 
+        if (sd_seat_can_multi_session (seat_id))
+                display = gdm_display_store_find (store, lookup_prepared_display_by_seat_id, (gpointer) seat_id);
+        else
+                display = gdm_display_store_find (store, lookup_by_seat_id, (gpointer) seat_id);
+
+        /* Ensure we don't create the same display more than once */
+        if (display != NULL) {
+                g_debug ("GdmLocalDisplayFactory: display already created");
+                return NULL;
+        }
+
         ret = sd_seat_get_active (seat_id, &active_session_id, NULL);
 
         if (ret == 0) {
                 char *login_session_id = NULL;
 
                 /* If we already have a login window, switch to it */
                 if (gdm_get_login_window_session_id (seat_id, &login_session_id)) {
                         GdmDisplay *display;
 
                         display = gdm_display_store_find (store,
                                                           lookup_by_session_id,
                                                           (gpointer) login_session_id);
                         if (display != NULL && gdm_display_get_status (display) == GDM_DISPLAY_MANAGED) {
                                 if (g_strcmp0 (active_session_id, login_session_id) != 0) {
                                         g_debug ("GdmLocalDisplayFactory: session %s found, activating.",
                                                  login_session_id);
                                         gdm_activate_session_by_id (factory->priv->connection, seat_id, login_session_id);
                                 }
                                 g_clear_pointer (&login_session_id, g_free);
                                 g_clear_pointer (&active_session_id, g_free);
                                 return NULL;
                         }
                         g_clear_pointer (&login_session_id, g_free);
                 }
                 g_clear_pointer (&active_session_id, g_free);
-        } else if (!sd_seat_can_multi_session (seat_id)) {
-                /* Ensure we don't create the same display more than once */
-                display = gdm_display_store_find (store, lookup_by_seat_id, (gpointer) seat_id);
-
-                if (display != NULL) {
-                        return NULL;
-                }
         }
 
         g_debug ("GdmLocalDisplayFactory: Adding display on seat %s", seat_id);
 
 #ifdef ENABLE_USER_DISPLAY_SERVER
         if (g_strcmp0 (seat_id, "seat0") == 0) {
                 display = gdm_local_display_new ();
                 if (session_type != NULL) {
                         g_object_set (G_OBJECT (display), "session-type", session_type, NULL);
                 }
         }
 #endif
 
         if (display == NULL) {
                 guint32 num;
 
                 num = take_next_display_number (factory);
 
                 display = gdm_legacy_display_new (num);
         }
 
         g_object_set (display, "seat-id", seat_id, NULL);
         g_object_set (display, "is-initial", initial, NULL);
 
         store_display (factory, display);
 
         /* let store own the ref */
         g_object_unref (display);
 
         if (! gdm_display_manage (display)) {
-- 
2.17.1