tree: https://git.kernel.org/pub/scm/linux/kernel/git/jfern/linux.git coresched head: 0cae4d526e66a8aa5f8b3626045be344860e9b8d commit: 0cae4d526e66a8aa5f8b3626045be344860e9b8d [12/12] FIXUP: Add a ht_protect= kernel cmdline option. config: i386-defconfig (attached as .config) compiler: gcc-9 (Debian 9.3.0-15) 9.3.0 reproduce (this is a W=1 build): # https://git.kernel.org/pub/scm/linux/kernel/git/jfern/linux.git/commit/?i... git remote add jfern https://git.kernel.org/pub/scm/linux/kernel/git/jfern/linux.git git fetch --no-tags jfern coresched git checkout 0cae4d526e66a8aa5f8b3626045be344860e9b8d # save the attached .config to linux build tree make W=1 ARCH=i386 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 >>): ld: kernel/sched/core.o: in function `sched_core_get': core.c:(.text+0x4098): undefined reference to `__sched_core_enabled' ld: kernel/sched/core.o: in function `sched_core_put': core.c:(.text+0x40f7): undefined reference to `__sched_core_enabled' ld: kernel/sched/core.o:(__jump_table+0x14): undefined reference to `__sched_core_enabled' ld: kernel/sched/core.o:(__jump_table+0x20): undefined reference to `__sched_core_enabled' ld: kernel/sched/core.o:(__jump_table+0x2c): more undefined references to `__sched_core_enabled' follow --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org