[kbuild-all] ERROR: modpost: "rcu_idle_enter" undefined!

tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master head: 325d0eab4f31c6240b59d5b2b8042c88f59405b5 commit: 1fecfdbb7acc6624655450a609221c89b5197a06 ACPI: processor: Take over RCU-idle for C3-BM idle date: 4 days ago config: ia64-defconfig (attached as .config) compiler: ia64-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 1fecfdbb7acc6624655450a609221c89b5197a06 # save the attached .config to linux build tree COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross ARCH=ia64 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 <<): --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org