OpenBSD, thanks to Tim Wiess
diff --git a/src/libthread/BSD.c b/src/libthread/BSD.c
index 2679cd2..0bc1905 100644
--- a/src/libthread/BSD.c
+++ b/src/libthread/BSD.c
@@ -90,6 +90,14 @@
 	lock((Lock*)&lk->access_lock);
 }
 
+void
+_spinunlock(spinlock_t *lk)
+{
+	unlock((Lock*)&lk->access_lock);
+}
+
+
+
 /*
  * sleep and wakeup
  */