From 2f776d679faa065f5998c17b6dbf23780773f8e9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Sebastian=20Dr=C3=B6ge?= <sebastian@centricular.com>
Date: Tue, 5 Jan 2016 14:23:26 +0200
Subject: [PATCH] clock: Don't allow setting an unsynced clock as master

---
 gst/gstclock.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/gst/gstclock.c b/gst/gstclock.c
index d3eaf9df57..70583c4a5c 100644
--- a/gst/gstclock.c
+++ b/gst/gstclock.c
@@ -1230,6 +1230,9 @@ gst_clock_set_master (GstClock * clock, GstClock * master)
   /* we always allow setting the master to NULL */
   if (master && !GST_OBJECT_FLAG_IS_SET (clock, GST_CLOCK_FLAG_CAN_SET_MASTER))
     goto not_supported;
+  if (master && !gst_clock_is_synced (master))
+    goto master_not_synced;
+
   GST_CAT_DEBUG_OBJECT (GST_CAT_CLOCK, clock,
       "slaving %p to master clock %p", clock, master);
   GST_OBJECT_UNLOCK (clock);
@@ -1270,6 +1273,14 @@ not_supported:
     GST_OBJECT_UNLOCK (clock);
     return FALSE;
   }
+
+master_not_synced:
+  {
+    GST_CAT_DEBUG_OBJECT (GST_CAT_CLOCK, master,
+        "master clock is not synced yet");
+    GST_OBJECT_UNLOCK (clock);
+    return FALSE;
+  }
 }
 
 /**