[gdm/wip/systemd-activation: 4/4] worker: reuse user's VT if available

[Ray Strode <halfline src gnome org>]

commit 01d96822282eac1950b9b0c7466635f7113e3b1f
Author: Ray Strode <rstrode redhat com>
Date:   Mon Apr 28 16:21:47 2014 -0400

    worker: reuse user's VT if available
    
    When a user logs out, their session goes into the closing
    state until all processes from the session exit. The X server
    won't exit while the session is in the closing state, but will
    instead reset itself.  When the user logs in again, we need to
    select the same VT so the already running X server can properly
    manage the new session.
    
    This commit checks for the above scenario and tries to account
    for it.

 daemon/gdm-session-worker.c |  112 +++++++++++++++++++++++++++++++++++++++++-
 1 files changed, 109 insertions(+), 3 deletions(-)
---
diff --git a/daemon/gdm-session-worker.c b/daemon/gdm-session-worker.c
index c3de148..2277e5f 100644
--- a/daemon/gdm-session-worker.c
+++ b/daemon/gdm-session-worker.c
@@ -52,6 +52,7 @@
 
 #ifdef WITH_SYSTEMD
 #include <systemd/sd-daemon.h>
+#include <systemd/sd-login.h>
 #endif
 
 #ifdef ENABLE_SYSTEMD_JOURNAL
@@ -1984,6 +1985,105 @@ gdm_session_worker_start_session (GdmSessionWorker  *worker,
 
 #ifdef ENABLE_WAYLAND_SUPPORT
 static gboolean
+validate_session (GdmSessionWorker *worker,
+                  const char       *session,
+                  const char       *requested_seat,
+                  const char       *requested_type,
+                  const char       *requested_state)
+{
+    int ret;
+    gboolean validated = FALSE;
+    char *state = NULL, *type = NULL, *seat = NULL;
+    uid_t uid;
+    unsigned int vt;
+
+    ret = sd_session_get_uid (session, &uid);
+
+    if (ret < 0 || uid != worker->priv->uid) {
+            goto out;
+    }
+
+    ret = sd_session_get_state (session, &state);
+
+    if (ret < 0 || state == NULL) {
+            goto out;
+    }
+
+    if (strcmp (state, requested_state) != 0) {
+            goto out;
+    }
+
+    ret = sd_session_get_type (session, &type);
+
+    if (ret < 0 || type == NULL) {
+            goto out;
+    }
+
+    if (strcmp (type, requested_type) != 0) {
+            goto out;
+    }
+
+    ret = sd_session_get_seat (session, &seat);
+
+    if (ret < 0 || seat == NULL) {
+            goto out;
+    }
+
+    if (strcmp (seat, requested_seat) != 0) {
+            goto out;
+    }
+
+    ret = sd_session_get_vt (session, &vt);
+
+    if (ret < 0 || vt <= 0) {
+            goto out;
+    }
+
+    validated = TRUE;
+
+out:
+    free (state);
+    free (type);
+    free (seat);
+    return validated;
+}
+
+static int
+find_vt_of_closing_session (GdmSessionWorker *worker)
+{
+        char **sessions = NULL;
+        unsigned int vt = 0;
+        int ret;
+        int i;
+
+        ret = sd_seat_get_sessions (worker->priv->display_seat_id, &sessions, NULL, NULL);
+
+        if (ret < 0 || sessions == NULL) {
+                goto out;
+        }
+
+        for (i = 0; sessions[i] != NULL; i++) {
+                if (vt == 0) {
+                        gboolean validated;
+                        validated = validate_session (worker, sessions[i], worker->priv->display_seat_id, 
"x11", "closing");
+
+                        if (validated) {
+                                ret = sd_session_get_vt (sessions[i], &vt);
+
+                                if (ret < 0) {
+                                        vt = 0;
+                                }
+                        }
+                }
+                free(sessions[i]);
+        }
+        free (sessions);
+
+out:
+        return (int) vt;
+}
+
+static gboolean
 set_up_for_new_vt (GdmSessionWorker *worker)
 {
         int fd;
@@ -2004,9 +2104,15 @@ set_up_for_new_vt (GdmSessionWorker *worker)
                 goto fail;
         }
 
-        if (ioctl(fd, VT_OPENQRY, &session_vt) < 0) {
-                g_debug ("GdmSessionWorker: couldn't open new VT: %m");
-                goto fail;
+        /* First adopt any pre-existing VT own by a session going down
+         */
+        session_vt = find_vt_of_closing_session (worker);
+
+        if (session_vt <= 0) {
+                if (ioctl(fd, VT_OPENQRY, &session_vt) < 0) {
+                        g_debug ("GdmSessionWorker: couldn't open new VT: %m");
+                        goto fail;
+                }
         }
 
         worker->priv->login_vt = vt_state.v_active;