tree: https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git dev.2020.12.23a head: 7cc07f4867eb9618d4f7c35ddfbd746131b52f51 commit: 6a70298420b2bd6d3e3dc86d81b993f618df8569 [133/149] clocksource: Check per-CPU clock synchronization when marked unstable config: x86_64-randconfig-r013-20201223 (attached as .config) compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project cee1e7d14f4628d6174b33640d502bff3b54ae45) 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 x86_64 cross compiling tool for clang build # apt-get install binutils-x86-64-linux-gnu # https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git/commit/?id=6a70298420b2bd6d3e3dc86d81b993f618df8569 git remote add rcu https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git git fetch --no-tags rcu dev.2020.12.23a git checkout 6a70298420b2bd6d3e3dc86d81b993f618df8569 # save the attached .config to linux build tree COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=x86_64 If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot All warnings (new ones prefixed by >>): >> kernel/time/clocksource.c:220:6: warning: no previous prototype for function 'clocksource_verify_one_cpu' [-Wmissing-prototypes] void clocksource_verify_one_cpu(void *csin) ^ kernel/time/clocksource.c:220:1: note: declare 'static' if the function is not intended to be used outside of this translation unit void clocksource_verify_one_cpu(void *csin) ^ static 1 warning generated. vim +/clocksource_verify_one_cpu +220 kernel/time/clocksource.c 219 > 220 void clocksource_verify_one_cpu(void *csin) 221 { 222 struct clocksource *cs = (struct clocksource *)csin; 223 224 __this_cpu_write(csnow_mid, cs->read(cs)); 225 } 226 --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org