Index: kernel/generic/include/proc/thread.h
===================================================================
--- kernel/generic/include/proc/thread.h	(revision de33dab3d6e266b32bfcf983b683fc6d18b2ac72)
+++ kernel/generic/include/proc/thread.h	(revision 4365d108fca11d735aaf46f7098b7f1d5c2cbb52)
@@ -54,5 +54,9 @@
 /* Thread flags */
 
-/** Thread cannot be migrated to another CPU. */
+/** Thread cannot be migrated to another CPU.
+ *
+ * When using this flag, the caller must set cpu in the thread_t
+ * structure manually before calling thread_ready (even on uniprocessor).
+ */ 
 #define THREAD_FLAG_WIRED	(1 << 0)
 /** Thread was migrated to another CPU and has not run yet. */
Index: kernel/generic/src/proc/thread.c
===================================================================
--- kernel/generic/src/proc/thread.c	(revision de33dab3d6e266b32bfcf983b683fc6d18b2ac72)
+++ kernel/generic/src/proc/thread.c	(revision 4365d108fca11d735aaf46f7098b7f1d5c2cbb52)
@@ -239,4 +239,5 @@
 	cpu = CPU;
 	if (t->flags & THREAD_FLAG_WIRED) {
+		ASSERT(t->cpu != NULL);
 		cpu = t->cpu;
 	}