tree: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master head: fb57b1fabcb28f358901b2df90abd2b48abc1ca8 commit: aa3238a152d1646868ac81bee4eee08ba39594de [9340/10701] mm: free_area_init: allow defining max_zone_pfn in descending order config: arc-randconfig-r011-20200519 (attached as .config) compiler: arc-elf-gcc (GCC) 9.3.0 reproduce: wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross chmod +x ~/bin/make.cross git checkout aa3238a152d1646868ac81bee4eee08ba39594de # save the attached .config to linux build tree COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross ARCH=arc If you fix the issue, kindly add following tag as appropriate Reported-by: kbuild test robot <lkp(a)intel.com&gt; All warnings (new ones prefixed by >>, old ones prefixed by <<): arch/arc/mm/init.c:39:13: warning: no previous prototype for 'arc_get_mem_sz' [-Wmissing-prototypes] 39 | long __init arc_get_mem_sz(void) | ^~~~~~~~~~~~~~ 80 | bool arch_has_descending_max_zone_pfns(void) | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ arch/arc/mm/init.c:91:13: warning: no previous prototype for 'setup_arch_memory' [-Wmissing-prototypes] 91 | void __init setup_arch_memory(void) | ^~~~~~~~~~~~~~~~~ vim +/arch_has_descending_max_zone_pfns +80 arch/arc/mm/init.c 79 81 { 82 return true; 83 } 84 --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org