tree: https://git.kernel.org/pub/scm/linux/kernel/git/jolsa/perf.git ftrace/direct head: b171ddeaf8fd82ae5e703a9ec28dc4a44f8f0019 commit: b171ddeaf8fd82ae5e703a9ec28dc4a44f8f0019 [8/8] ftrace/samples: Add multi direct interface test module config: x86_64-allyesconfig (attached as .config) compiler: gcc-9 (Debian 9.3.0-22) 9.3.0 reproduce (this is a W=1 build): # https://git.kernel.org/pub/scm/linux/kernel/git/jolsa/perf.git/commit/?id... git remote add jolsa-perf https://git.kernel.org/pub/scm/linux/kernel/git/jolsa/perf.git git fetch --no-tags jolsa-perf ftrace/direct git checkout b171ddeaf8fd82ae5e703a9ec28dc4a44f8f0019 # save the attached .config to linux build tree make 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 errors (new ones prefixed by >>): 8 | void my_direct_func(unsigned long ip) | ^~~~~~~~~~~~~~ cc1: all warnings being treated as errors vim +/my_direct_func +8 samples/ftrace/ftrace-direct-multi.c 7 9 { 10 trace_printk("ip %lx\n", ip); 11 } 12 --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org