tree: https://git.kernel.org/pub/scm/linux/kernel/git/mark/linux.git locking/debug-refcount head: fb4984c339109f2ee2dd0000e7744aab91b974f5 commit: 488dd36233a4a0d80f516054ee894688fc8f447f [1/3] WIP: add DEBUG_REFCOUNT config: x86_64-randconfig-m031-20211218 (https://download.01.org/0day-ci/archive/20211219/202112190815.A03KAOQo-lk...) compiler: gcc-9 (Debian 9.3.0-22) 9.3.0 reproduce (this is a W=1 build): # https://git.kernel.org/pub/scm/linux/kernel/git/mark/linux.git/commit/?id... git remote add mark https://git.kernel.org/pub/scm/linux/kernel/git/mark/linux.git git fetch --no-tags mark locking/debug-refcount git checkout 488dd36233a4a0d80f516054ee894688fc8f447f # save the config file to linux build tree mkdir build_dir make W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot <lkp(a)intel.com&gt; All errors (new ones prefixed by >>, old ones prefixed by <<): ERROR: modpost: "refcount_bad_magic" [fs/nfs/nfsv4.ko] undefined! --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org