tree: https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git dev.2020.12.15b head: f895a17eec290b0038a6294d884a9cc92d7d6e80 commit: 7655dc620982c6505386efdaf975e6bde3c27afb [130/134] rcu-tasks: Use NULL pointer instead of empty show_rcu_tasks_*() functions config: ia64-randconfig-r012-20201217 (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 # https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git/commit/?id=7655dc620982c6505386efdaf975e6bde3c27afb git remote add rcu https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git git fetch --no-tags rcu dev.2020.12.15b git checkout 7655dc620982c6505386efdaf975e6bde3c27afb # 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 All errors (new ones prefixed by >>): In file included from arch/ia64/include/asm/pgtable.h:154, from include/linux/pgtable.h:6, from arch/ia64/include/asm/uaccess.h:40, from include/linux/uaccess.h:11, from arch/ia64/include/asm/sections.h:11, from include/linux/interrupt.h:20, from kernel/rcu/update.c:25: arch/ia64/include/asm/mmu_context.h: In function 'reload_context': arch/ia64/include/asm/mmu_context.h:137:41: warning: variable 'old_rr4' set but not used [-Wunused-but-set-variable] 137 | unsigned long rr0, rr1, rr2, rr3, rr4, old_rr4; | ^~~~~~~ In file included from include/uapi/linux/posix_types.h:5, from include/uapi/linux/types.h:14, from include/linux/types.h:6, from kernel/rcu/update.c:20: kernel/rcu/tasks.h: In function 'show_rcu_tasks_gp_kthreads': >> include/linux/stddef.h:8:14: error: called object is not a function or function pointer 8 | #define NULL ((void *)0) | ^ kernel/rcu/rcu.h:554:40: note: in expansion of macro 'NULL' 554 | #define show_rcu_tasks_rude_gp_kthread NULL | ^~~~ kernel/rcu/tasks.h:1222:2: note: in expansion of macro 'show_rcu_tasks_rude_gp_kthread' 1222 | show_rcu_tasks_rude_gp_kthread(); | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ >> include/linux/stddef.h:8:14: error: called object is not a function or function pointer 8 | #define NULL ((void *)0) | ^ kernel/rcu/rcu.h:559:41: note: in expansion of macro 'NULL' 559 | #define show_rcu_tasks_trace_gp_kthread NULL | ^~~~ kernel/rcu/tasks.h:1223:2: note: in expansion of macro 'show_rcu_tasks_trace_gp_kthread' 1223 | show_rcu_tasks_trace_gp_kthread(); | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ vim +8 include/linux/stddef.h ^1da177e4c3f415 Linus Torvalds 2005-04-16 6 ^1da177e4c3f415 Linus Torvalds 2005-04-16 7 #undef NULL ^1da177e4c3f415 Linus Torvalds 2005-04-16 @8 #define NULL ((void *)0) 6e2182874324727 Richard Knutsson 2006-09-30 9 :::::: The code at line 8 was first introduced by commit :::::: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 Linux-2.6.12-rc2 :::::: TO: Linus Torvalds :::::: CC: Linus Torvalds --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org