Hi Vincent, FYI, the error/warning still remains. tree: https://android.googlesource.com/kernel/common android12-5.10-2021-09 head: cac628d5320f43641e9fb9285d972060b61ca2de commit: 683010f555d804c2b9b01d327767755fa78a3ce5 [1943/10852] ANDROID: cpu/hotplug: add pause/resume_cpus interface config: x86_64-randconfig-r033-20210928 (attached as .config) compiler: clang version 14.0.0 (https://github.com/llvm/llvm-project dc6e8dfdfe7efecfda318d43a06fae18b40eb498) 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 remote add android-common https://android.googlesource.com/kernel/common git fetch --no-tags android-common android12-5.10-2021-09 git checkout 683010f555d804c2b9b01d327767755fa78a3ce5 # save the attached .config to linux build tree COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 ARCH=x86_64 If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot <lkp(a)intel.com&gt; All warnings (new ones prefixed by >>): kernel/sched/core.c:2410:6: warning: no previous prototype for function 'sched_set_stop_task' [-Wmissing-prototypes] void sched_set_stop_task(int cpu, struct task_struct *stop) ^ kernel/sched/core.c:2410:1: note: declare 'static' if the function is not intended to be used outside of this translation unit void sched_set_stop_task(int cpu, struct task_struct *stop) ^ static kernel/sched/core.c:4690:35: warning: no previous prototype for function 'schedule_user' [-Wmissing-prototypes] asmlinkage __visible void __sched schedule_user(void) ^ kernel/sched/core.c:4690:22: note: declare 'static' if the function is not intended to be used outside of this translation unit asmlinkage __visible void __sched schedule_user(void) ^ static int _sched_cpu_deactivate(unsigned int cpu) ^ kernel/sched/core.c:6995:1: note: declare 'static' if the function is not intended to be used outside of this translation unit int _sched_cpu_deactivate(unsigned int cpu) ^ static kernel/sched/core.c:330:1: warning: unused function 'rq_csd_init' [-Wunused-function] rq_csd_init(struct rq *rq, call_single_data_t *csd, smp_call_func_t func) ^ 4 warnings generated. vim +/_sched_cpu_deactivate +6995 kernel/sched/core.c 6994 6996 { 6997 int ret; 6998 6999 set_cpu_active(cpu, false); 7000 --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org