tree: https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git sched/migrate-disable head: c777d847107e80df24dae87fc9cf4b4c0bf4dfed commit: 1cf12e08bc4d50a76b80c42a3109c53d8794a0c9 [6/18] sched/hotplug: Consolidate task migration on CPU unplug config: mips-randconfig-r026-20201209 (attached as .config) compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project 1968804ac726e7674d5de22bc2204b45857da344) 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/tip/tip.git/commit/?id=1c... git remote add tip https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git git fetch --no-tags tip sched/migrate-disable git checkout 1cf12e08bc4d50a76b80c42a3109c53d8794a0c9 # save the attached .config to linux build tree COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=mips If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot <lkp(a)intel.com&gt; All warnings (new ones prefixed by >>): kernel/sched/core.c:2376:6: warning: no previous prototype for function 'sched_set_stop_task' void sched_set_stop_task(int cpu, struct task_struct ^ kernel/sched/core.c:2376:1: note: declare 'static' if the function is not intended to be used outside of this translation unit void sched_set_stop_task(int cpu, struct task_struct ^ static kernel/sched/core.c:324:1: warning: unused function 'rq_csd_init' rq_csd_init(struct rq call_single_data_t smp_call_func_t func) ^ kernel/sched/core.c:4196:20: warning: unused function 'sched_tick_stop' static inline void sched_tick_stop(int cpu) { } ^ static inline void balance_hotplug_wait(void) ^ fatal error: error in backend: Nested variants found in inline asm string: ' .set push .set noat .set push .set arch=r4000 .if ( 0x00 ) != -1)) 0x00 ) != -1)) : ($( 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-12: error: clang frontend command failed with exit code 70 (use -v to see invocation) clang version 12.0.0 (git://gitmirror/llvm_project 1968804ac726e7674d5de22bc2204b45857da344) Target: mipsel-unknown-linux-gnu Thread model: posix InstalledDir: /opt/cross/clang-1968804ac7/bin clang-12: note: diagnostic msg: Makefile arch drivers fs include kernel net scripts source usr vim +/balance_hotplug_wait +6854 kernel/sched/core.c 2558aacff85866 Peter Zijlstra 2020-09-11 6853 f2469a1fb43f85 Thomas Gleixner 2020-09-14 @6854 static inline void balance_hotplug_wait(void) f2469a1fb43f85 Thomas Gleixner 2020-09-14 6855 { f2469a1fb43f85 Thomas Gleixner 2020-09-14 6856 } f2469a1fb43f85 Thomas Gleixner 2020-09-14 6857 :::::: The code at line 6854 was first introduced by commit :::::: f2469a1fb43f85d243ce72638367fb6e15c33491 sched/core: Wait for tasks being pushed away on hotplug :::::: TO: Thomas Gleixner <tglx(a)linutronix.de&gt; :::::: CC: Peter Zijlstra <peterz(a)infradead.org&gt; --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org