src/Pure/Concurrent/consumer_thread.scala

--- a/src/Pure/Concurrent/consumer_thread.scala	Wed Jun 14 16:03:02 2017 +0200
+++ b/src/Pure/Concurrent/consumer_thread.scala	Fri Jun 16 15:59:27 2017 +0200
@@ -33,6 +33,7 @@
 
   private val thread = Standard_Thread.fork(name, daemon) { main_loop(Nil) }
   def is_active: Boolean = active && thread.isAlive
+  def check_thread: Boolean = Thread.currentThread == thread
 
   private def failure(exn: Throwable): Unit =
     Output.error_message(