diff -r 12070638fe29 -r ead544f3d6a1 src/Pure/Tools/isabelle_process.scala
--- a/src/Pure/Tools/isabelle_process.scala	Tue Jan 27 19:56:26 2009 +0100
+++ b/src/Pure/Tools/isabelle_process.scala	Wed Jan 28 10:43:31 2009 +0100
@@ -118,10 +118,10 @@
 
   /* process information */
 
-  private var proc: Process = null
-  private var closing = false
-  private var pid: String = null
-  private var the_session: String = null
+  @volatile private var proc: Process = null
+  @volatile private var closing = false
+  @volatile private var pid: String = null
+  @volatile private var the_session: String = null
   def session = the_session