tree: https://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git sched/urgent head: 0602ec6c74e25dcb8a43961b00eef168fafb8e5e commit: 0602ec6c74e25dcb8a43961b00eef168fafb8e5e [7/7] smp: Cleanup smp_call_function*() config: mips-randconfig-r026-20200615 (attached as .config) compiler: clang version 11.0.0 (https://github.com/llvm/llvm-project 3d8149c2a1228609fd7d7c91a04681304a2f0ca9) reproduce (this is a W=1 build): wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross chmod +x ~/bin/make.cross # install mips cross compiling tool for clang build # apt-get install binutils-mips-linux-gnu git checkout 0602ec6c74e25dcb8a43961b00eef168fafb8e5e # save the attached .config to linux build tree COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=mips 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 <<): arch/mips/kernel/process.c:96:5: warning: no previous prototype for function 'arch_dup_task_struct' [-Wmissing-prototypes] int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src) ^ arch/mips/kernel/process.c:96:1: note: declare 'static' if the function is not intended to be used outside of this translation unit int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src) ^ static arch/mips/kernel/process.c:682:15: warning: no previous prototype for function 'arch_align_stack' [-Wmissing-prototypes] unsigned long arch_align_stack(unsigned long sp) ^ arch/mips/kernel/process.c:682:1: note: declare 'static' if the function is not intended to be used outside of this translation unit unsigned long arch_align_stack(unsigned long sp) ^ static static DEFINE_PER_CPU(call_single_data_t, backtrace_csd) = CSD_INIT(handle_backtrace, NULL); ^~~~~~~~~~~~~~~~ sprint_backtrace include/linux/smp.h:30:40: note: expanded from macro 'CSD_INIT' (struct __call_single_data){ .func = (_func), .info = (_info), } ^ include/linux/kallsyms.h:95:12: note: 'sprint_backtrace' declared here extern int sprint_backtrace(char *buffer, unsigned long address); ^ static DEFINE_PER_CPU(call_single_data_t, backtrace_csd) = CSD_INIT(handle_backtrace, NULL); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ include/linux/smp.h:30:39: note: expanded from macro 'CSD_INIT' (struct __call_single_data){ .func = (_func), .info = (_info), } ^~~~~~~ 2 warnings and 2 errors generated. vim +690 arch/mips/kernel/process.c 677 678 /* 679 * Don't forget that the stack pointer must be aligned on a 8 bytes 680 * boundary for 32-bits ABI and 16 bytes for 64-bits ABI. 681 */ 683 { 684 if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space) 685 sp -= get_random_int() & ~PAGE_MASK; 686 687 return sp & ALMASK; 688 } 689 691 static struct cpumask backtrace_csd_busy; 692 --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org