+#ifdef LISP_FEATURE_SB_THREAD
+void
+arch_os_load_ldt(struct thread *thread)
+{
+ int sel = LSEL(thread->tls_cookie, SEL_UPL);
+ unsigned int fs = rfs();
+
+ /* Load FS only if it's necessary. Modifying a selector
+ * causes privilege checking and it takes long time. */
+ if (fs != sel)
+ load_fs(sel);
+}
+#endif
+