From 24dc214f55e7c7c17d888d0ccf94cd3625767462 Mon Sep 17 00:00:00 2001
From: Michael Biebl <biebl@debian.org>
Date: Mon, 20 Sep 2010 00:45:16 +0200
Subject: linux: Check for VT_WAITEVENT ioctl during runtime

Since 2782cc8d4950effbc4407455e72bd4750cef6e11 ConsoleKit fails, if it
has been compiled on a linux kernel >= 2.6.32 but is run with an older
kernel. Check for VT_WAITEVENT ioctl during runtime and fallback to the
old behaviour of creating a thread for every possible vt.
---
 src/ck-vt-monitor.c | 58 ++++++++++++++++++++++++++++++++++++++++++++---------
 1 file changed, 49 insertions(+), 9 deletions(-)

diff --git a/src/ck-vt-monitor.c b/src/ck-vt-monitor.c
index 369c63e..9310341 100644
--- a/src/ck-vt-monitor.c
+++ b/src/ck-vt-monitor.c
@@ -27,6 +27,7 @@
 #include <string.h>
 #include <errno.h>
 #include <signal.h>
+#include <sys/ioctl.h>
 
 #include <glib.h>
 #include <glib/gi18n.h>
@@ -311,6 +312,34 @@ schedule_process_queue (CkVtMonitor *vt_monitor)
         G_UNLOCK (schedule_lock);
 }
 
+#ifdef VT_WAITEVENT
+static gboolean
+vt_waitevent_supported (int fd)
+{
+        static int supported = -1;
+        int res;
+
+        if (supported >= 0)
+                return supported;
+
+        res = ioctl(fd, VT_WAITEVENT, NULL);
+
+        if (res == ERROR) {
+                if (errno == EINVAL) {
+                        g_debug ("VT_WAITEVENT not supported on this system");
+                        supported = FALSE;
+                        return FALSE;
+                } else if (errno == EFAULT) {
+                        g_debug ("VT_WAITEVENT supported on this system");
+                        supported = TRUE;
+                        return TRUE;
+                }
+        }
+        g_debug ("Unexpected result for VT_WAITEVENT check, returning FALSE");
+        return FALSE;
+}
+#endif
+
 static void *
 vt_thread_start (ThreadData *data)
 {
@@ -322,6 +351,9 @@ vt_thread_start (ThreadData *data)
         num = data->num;
 
 #ifdef VT_WAITEVENT
+        if (!vt_waitevent_supported(vt_monitor->priv->vfd))
+                goto no_waitevent;
+
         for (;;) {
                 res = ck_wait_for_console_switch (vt_monitor->priv->vfd, &num);
                 if (! res) {
@@ -340,7 +372,10 @@ vt_thread_start (ThreadData *data)
                         schedule_process_queue (vt_monitor);
                 }
         }
-#else
+        goto out;
+#endif
+
+no_waitevent:
         res = ck_wait_for_active_console_num (vt_monitor->priv->vfd, num);
         if (! res) {
                 /* FIXME: what do we do if it fails? */
@@ -357,8 +392,8 @@ vt_thread_start (ThreadData *data)
                 /* schedule processing of queue */
                 schedule_process_queue (vt_monitor);
         }
-#endif
 
+out:
         G_LOCK (hash_lock);
         if (vt_monitor->priv->vt_thread_hash != NULL) {
                 g_hash_table_remove (vt_monitor->priv->vt_thread_hash, GUINT_TO_POINTER (num));
@@ -418,19 +453,24 @@ vt_add_watches (CkVtMonitor *vt_monitor)
         sigaction (SIGPOLL, &act, NULL);
 
         ioctl (vt_monitor->priv->vfd, I_SETSIG, S_MSG);
-#elif defined (VT_WAITEVENT)
+#else
+        guint  max_consoles;
+        int    i;
+        gint32 current_num;
         gpointer id;
 
+#if defined (VT_WAITEVENT)
+        if (!vt_waitevent_supported(vt_monitor->priv->vfd))
+                goto no_waitevent;
+
         G_LOCK (hash_lock);
         id = GINT_TO_POINTER (1);
         if (g_hash_table_lookup (vt_monitor->priv->vt_thread_hash, id) == NULL)
                 vt_add_watch_unlocked (vt_monitor, 1);
-        G_UNLOCK (hash_lock);
-#else
-        guint  max_consoles;
-        int    i;
-        gint32 current_num;
+        goto out;
+#endif
 
+no_waitevent:
         G_LOCK (hash_lock);
 
         current_num = vt_monitor->priv->active_num;
@@ -442,7 +482,6 @@ vt_add_watches (CkVtMonitor *vt_monitor)
         }
 
         for (i = 1; i < max_consoles; i++) {
-                gpointer id;
 
                 /* don't wait on the active vc */
                 if (i == current_num) {
@@ -457,6 +496,7 @@ vt_add_watches (CkVtMonitor *vt_monitor)
                 }
         }
 
+out:
         G_UNLOCK (hash_lock);
 #endif
 }
-- 
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