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-allyesconfig (attached as .config) compiler: mips-linux-gcc (GCC) 9.3.0 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 git checkout 0602ec6c74e25dcb8a43961b00eef168fafb8e5e # save the attached .config to linux build tree COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 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 'arch_dup_task_struct' [-Wmissing-prototypes] 96 | int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src) | ^~~~~~~~~~~~~~~~~~~~ arch/mips/kernel/process.c:682:15: warning: no previous prototype for 'arch_align_stack' [-Wmissing-prototypes] 682 | unsigned long arch_align_stack(unsigned long sp) | ^~~~~~~~~~~~~~~~ In file included from arch/mips/include/asm/cpu-type.h:12, from arch/mips/include/asm/timex.h:19, from include/linux/timex.h:65, from include/linux/time32.h:13, from include/linux/time.h:74, from include/linux/ktime.h:24, from include/linux/timer.h:6, from include/linux/workqueue.h:9, from include/linux/rhashtable-types.h:15, from include/linux/ipc.h:7, from include/uapi/linux/sem.h:5, from include/linux/sem.h:5, from include/linux/sched.h:15, from arch/mips/kernel/process.c:13: 690 | static DEFINE_PER_CPU(call_single_data_t, backtrace_csd) = CSD_INIT(handle_backtrace, NULL); | ^~~~~~~~~~~~~~~~ include/linux/smp.h:30:40: note: in definition of macro 'CSD_INIT' 30 | (struct __call_single_data){ .func = (_func), .info = (_info), } | ^~~~~ arch/mips/kernel/process.c:693:13: warning: 'handle_backtrace' defined but not used [-Wunused-function] 693 | static void handle_backtrace(void *info) | ^~~~~~~~~~~~~~~~ vim +/handle_backtrace +690 arch/mips/kernel/process.c 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