Index: kernel/generic/include/time/timeout.h
===================================================================
--- kernel/generic/include/time/timeout.h	(revision 46b305ad06b46ff90c280b198a0339a0ea00df22)
+++ kernel/generic/include/time/timeout.h	(revision 11d2c98362478850f6d9f3d23e3a07426ab94485)
@@ -53,4 +53,6 @@
 	/** On which processor is this timeout registered. */
 	cpu_t *cpu;
+	/** Used to synchronize with the handler callback. */
+	atomic_bool finished;
 } timeout_t;