tree:   https://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git sched/wchan
head:   48f17ab32afc56a67359efc5b8889cb8cb42ec80
commit: 48f17ab32afc56a67359efc5b8889cb8cb42ec80 [7/7] arch: Fix STACKTRACE_SUPPORT
config: mips-loongson1b_defconfig (attached as .config)
compiler: mipsel-linux-gcc (GCC) 11.2.0
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/peterz/queue.git/commit/?id=48f17ab32afc56a67359efc5b8889cb8cb42ec80
        git remote add peterz-queue https://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git
        git fetch --no-tags peterz-queue sched/wchan
        git checkout 48f17ab32afc56a67359efc5b8889cb8cb42ec80
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.2.0 make.cross 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 >>):

>> arch/mips/kernel/stacktrace.c:69:6: warning: no previous prototype for '__save_stack_trace_tsk' [-Wmissing-prototypes]
      69 | void __save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace, bool savesched)
         |      ^~~~~~~~~~~~~~~~~~~~~~


vim +/__save_stack_trace_tsk +69 arch/mips/kernel/stacktrace.c

    68	
  > 69	void __save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace, bool savesched)
    70	{
    71		struct pt_regs dummyregs;
    72		struct pt_regs *regs = &dummyregs;
    73	
    74		WARN_ON(trace->nr_entries || !trace->max_entries);
    75	
    76		if (tsk != current) {
    77			regs->regs[29] = tsk->thread.reg29;
    78			regs->regs[31] = 0;
    79			regs->cp0_epc = tsk->thread.reg31;
    80		} else
    81			prepare_frametrace(regs);
    82		save_context_stack(trace, tsk, regs, savesched);
    83	}
    84	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org