tree:   https://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git sched/wchan
head:   48f17ab32afc56a67359efc5b8889cb8cb42ec80
commit: ad0e08bcd10f58d31e78e16d817bfc466e13ac66 [6/7] arch: __get_wchan || STACKTRACE_SUPPORT
config: ia64-defconfig (attached as .config)
compiler: ia64-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=ad0e08bcd10f58d31e78e16d817bfc466e13ac66
        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 ad0e08bcd10f58d31e78e16d817bfc466e13ac66
        # save the attached .config to linux build tree
        mkdir build_dir
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.2.0 make.cross O=build_dir ARCH=ia64 SHELL=/bin/bash

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

>> kernel/sched/core.c:1966:22: error: static declaration of '__get_wchan' follows non-static declaration
    1966 | static unsigned long __get_wchan(struct task_struct *p)
         |                      ^~~~~~~~~~~
   In file included from arch/ia64/include/asm/thread_info.h:12,
                    from include/linux/thread_info.h:60,
                    from include/asm-generic/preempt.h:5,
                    from ./arch/ia64/include/generated/asm/preempt.h:1,
                    from include/linux/preempt.h:78,
                    from include/linux/rcupdate.h:27,
                    from include/linux/rculist.h:11,
                    from include/linux/pid.h:5,
                    from include/linux/sched.h:14,
                    from include/linux/kthread.h:6,
                    from include/trace/events/sched.h:8,
                    from kernel/sched/core.c:10:
   arch/ia64/include/asm/processor.h:333:22: note: previous declaration of '__get_wchan' with type 'long unsigned int(struct task_struct *)'
     333 | extern unsigned long __get_wchan (struct task_struct *p);
         |                      ^~~~~~~~~~~
   kernel/sched/core.c:3450:6: warning: no previous prototype for 'sched_set_stop_task' [-Wmissing-prototypes]
    3450 | void sched_set_stop_task(int cpu, struct task_struct *stop)
         |      ^~~~~~~~~~~~~~~~~~~


vim +/__get_wchan +1966 kernel/sched/core.c

  1964	
  1965	#ifdef CONFIG_STACKTRACE
> 1966	static unsigned long __get_wchan(struct task_struct *p)
  1967	{
  1968		unsigned long entry = 0;
  1969	
  1970		stack_trace_save_tsk(p, &entry, 1, 0);
  1971	
  1972		return entry;
  1973	}
  1974	#endif
  1975	

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