Hi Thomas, FYI, the error/warning still remains. tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master head: 7f75285ca572eaabc028cf78c6ab5473d0d160be commit: 3015ef4b98f53fe7eba4f5f82f562c0e074d213c sched/core: Make migrate disable and CPU hotplug cooperative date: 5 months ago config: mips-randconfig-r023-20210414 (attached as .config) compiler: clang version 13.0.0 (https://github.com/llvm/llvm-project 9829f5e6b1bca9b61efc629770d28bb9014dec45) 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 mips cross compiling tool for clang build # apt-get install binutils-mips-linux-gnu # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit... git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git git fetch --no-tags linus master git checkout 3015ef4b98f53fe7eba4f5f82f562c0e074d213c # save the attached .config to linux build tree COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 ARCH=mips If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot <lkp(a)intel.com&gt; All warnings (new ones prefixed by >>): kernel/sched/core.c:4984:35: warning: no previous prototype for function 'schedule_user' asmlinkage __visible void __sched schedule_user(void) ^ kernel/sched/core.c:4984:22: note: declare 'static' if the function is not intended to be used outside of this translation unit asmlinkage __visible void __sched schedule_user(void) ^ static kernel/sched/core.c:324:1: warning: unused function 'rq_csd_init' rq_csd_init(struct rq call_single_data_t smp_call_func_t func) ^ kernel/sched/core.c:2704:20: warning: unused function 'is_migration_disabled' static inline bool is_migration_disabled(struct task_struct ^ static inline bool rq_has_pinned_tasks(struct rq ^ kernel/sched/core.c:4496:20: warning: unused function 'sched_tick_start' static inline void sched_tick_start(int cpu) { } ^ kernel/sched/core.c:4497:20: warning: unused function 'sched_tick_stop' static inline void sched_tick_stop(int cpu) { } ^ fatal error: error in backend: Nested variants found in inline asm string: ' .set push .set noat .set push .set arch=r4000 .if ( 0x00 ) != -1)) 0x00 ) != -1)) : ($( static struct ftrace_branch_data __attribute__((__aligned__(4))) __attribute__((__section__("_ftrace_branch"))) __if_trace = $( .func = __func__, .file = "arch/mips/include/asm/cmpxchg.h", .line = 163, $); 0x00 ) != -1)) : $))) ) && ( 0 ); .set push; .set mips64r2; .rept 1; sync 0x00; .endr; .set pop; .else; ; .endif 1: ll $0, $2 # __cmpxchg_asm bne $0, ${3:z}, 2f .set pop move $$1, ${4:z} .set arch=r4000 sc $$1, $1 beqz $$1, 1b .set pop 2: .if ( 0x00 ) != -1)) 0x00 ) != -1)) : ($( static struct ftrace_branch_data __attribute__((__aligned__(4))) __attribute__((__section__("_ftrace_branch"))) __if_trace = $( .func = __func__, .file = "arch/mips/include/asm/cmpxchg.h", .line = 163, $); 0x00 ) != -1)) : $))) ) && ( 0 ); .set push; .set mips64r2; .rept 1; sync 0x00; .endr; .set pop; .else; ; .endif ' clang-13: error: clang frontend command failed with exit code 70 (use -v to see invocation) clang version 13.0.0 (git://gitmirror/llvm_project 6a18cc23efad410db48a3ccfc233d215de7d4cb9) Target: mipsel-unknown-linux-gnu Thread model: posix InstalledDir: /opt/cross/clang-6a18cc23ef/bin clang-13: note: diagnostic msg: Makefile arch include kernel scripts source usr vim +/rq_has_pinned_tasks +2709 kernel/sched/core.c 2708 2710 { 2711 return false; 2712 } 2713 --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org