Index: kernel/generic/src/synch/futex.c
===================================================================
--- kernel/generic/src/synch/futex.c	(revision c98e6ee244a8e271a395a052069c23bca4f8b538)
+++ kernel/generic/src/synch/futex.c	(revision ce4a3dae093e94753a7db2c045dd2a93e9bf578f)
@@ -116,4 +116,5 @@
 	pte_t *t;
 	ipl_t ipl;
+	int rc;
 	
 	ipl = interrupts_disable();
@@ -135,7 +136,15 @@
 
 	futex = futex_find(paddr);
-	
-	return (unative_t) waitq_sleep_timeout(&futex->wq, usec, flags |
+
+#ifdef CONFIG_UDEBUG
+	udebug_stoppable_begin();
+#endif
+	rc = waitq_sleep_timeout(&futex->wq, usec, flags |
 	    SYNCH_FLAGS_INTERRUPTIBLE);
+
+#ifdef CONFIG_UDEBUG
+	udebug_stoppable_end();
+#endif
+	return (unative_t) rc;
 }