Index: src/synch/waitq.c
===================================================================
--- src/synch/waitq.c	(revision 43114c515872442297f5b1b8a327743ef24c825a)
+++ src/synch/waitq.c	(revision 47d78c6b7e84f7a6010baa23b8d356f10ea71f3f)
@@ -167,4 +167,5 @@
 			 * Short emulation of scheduler() return code.
 			 */
+			before_thread_runs();
 			spinlock_unlock(&THREAD->lock);
 			cpu_priority_restore(pri);