Index: subr_autoconf.c
===================================================================
RCS file: /cvsroot/src/sys/kern/subr_autoconf.c,v
retrieving revision 1.269
diff -u -p -r1.269 subr_autoconf.c
--- subr_autoconf.c	27 Feb 2020 20:16:38 -0000	1.269
+++ subr_autoconf.c	18 Apr 2020 13:07:49 -0000
@@ -511,7 +511,7 @@ config_create_mountrootthreads(void)
 	KASSERT(mountroot_config_lwpids);
 	for (i = 0; i < mountroot_config_threads; i++) {
 		mountroot_config_lwpids[i] = 0;
-		(void)kthread_create(PRI_NONE, KTHREAD_MUSTJOIN/* XXXSMP */,
+		(void)kthread_create(PRI_NONE, KTHREAD_MUSTJOIN|KTHREAD_MPSAFE,
 				     NULL, config_mountroot_thread, NULL,
 				     &mountroot_config_lwpids[i],
 				     "configroot");