diff -r 2d16c693d536 -r ef876972fdc1 src/Pure/Concurrent/task_queue.ML
--- a/src/Pure/Concurrent/task_queue.ML	Wed Aug 10 14:28:55 2011 +0200
+++ b/src/Pure/Concurrent/task_queue.ML	Wed Aug 10 15:17:24 2011 +0200
@@ -247,7 +247,7 @@
     val running =
       Tasks.fold (#1 #> get_job jobs #> (fn Running t => insert Thread.equal t | _ => I))
         (get_tasks groups (group_id group)) [];
-    val _ = List.app Simple_Thread.interrupt running;
+    val _ = List.app Simple_Thread.interrupt_unsynchronized running;
   in null running end;
 
 fun cancel_all (Queue {jobs, ...}) =
@@ -262,7 +262,7 @@
         | _ => (groups, running))
       end;
     val (running_groups, running) = Task_Graph.fold cancel_job jobs ([], []);
-    val _ = List.app Simple_Thread.interrupt running;
+    val _ = List.app Simple_Thread.interrupt_unsynchronized running;
   in running_groups end;