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/?id=3015ef4b98f53fe7eba4f5f82f562c0e074d213c
        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@intel.com>

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
   ^
>> kernel/sched/core.c:2709:20: warning: unused function 'rq_has_pinned_tasks'
   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	
> 2709	static inline bool rq_has_pinned_tasks(struct rq *rq)
  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