tree: https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git next head: 30df74d67d48949da87e3a5b57c381763e8fd526 commit: 29da4f91c0c1fbda12b8a31be0d564930208c92e [108/110] powerpc/watchpoint: Don't allow concurrent perf and ptrace events config: x86_64-allyesconfig (attached as .config) compiler: clang version 11.0.0 (https://github.com/llvm/llvm-project 135b877874fae96b4372c8a3fbfaa8ff44ff86e3) reproduce: 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 git checkout 29da4f91c0c1fbda12b8a31be0d564930208c92e # 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: kbuild test robot <lkp(a)intel.com&gt; All warnings (new ones prefixed by >>, old ones prefixed by <<): kernel/events/hw_breakpoint.c:71:12: warning: no previous prototype for function 'hw_breakpoint_weight' [-Wmissing-prototypes] __weak int hw_breakpoint_weight(struct perf_event *bp) ^ kernel/events/hw_breakpoint.c:71:8: note: declare 'static' if the function is not intended to be used outside of this translation unit __weak int hw_breakpoint_weight(struct perf_event *bp) ^ static __weak int arch_reserve_bp_slot(struct perf_event *bp) ^ kernel/events/hw_breakpoint.c:216:8: note: declare 'static' if the function is not intended to be used outside of this translation unit __weak int arch_reserve_bp_slot(struct perf_event *bp) ^ static __weak void arch_release_bp_slot(struct perf_event *bp) ^ kernel/events/hw_breakpoint.c:221:8: note: declare 'static' if the function is not intended to be used outside of this translation unit __weak void arch_release_bp_slot(struct perf_event *bp) ^ static kernel/events/hw_breakpoint.c:228:13: warning: no previous prototype for function 'arch_unregister_hw_breakpoint' [-Wmissing-prototypes] __weak void arch_unregister_hw_breakpoint(struct perf_event *bp) ^ kernel/events/hw_breakpoint.c:228:8: note: declare 'static' if the function is not intended to be used outside of this translation unit __weak void arch_unregister_hw_breakpoint(struct perf_event *bp) ^ static 4 warnings generated. vim +/arch_reserve_bp_slot +216 kernel/events/hw_breakpoint.c 215 217 { 218 return 0; 219 } 220 222 { 223 } 224 --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org