Hi Nicholas,

I love your patch! Yet something to improve:

[auto build test ERROR on openrisc/for-next]
[also build test ERROR on sparc/master linus/master asm-generic/master v5.8-rc7 next-20200727]
[cannot apply to nios2/for-linus]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/0day-ci/linux/commits/Nicholas-Piggin/Use-asm-generic-for-mmu_context-no-op-functions/20200728-113854
base:   https://github.com/openrisc/linux.git for-next
config: c6x-allyesconfig (attached as .config)
compiler: c6x-elf-gcc (GCC) 9.3.0
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
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross ARCH=c6x 

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 >>):

   In file included from ./arch/c6x/include/generated/asm/mmu_context.h:1,
                    from include/linux/mmu_context.h:5,
                    from kernel//sched/sched.h:54,
                    from kernel//sched/core.c:9:
   include/asm-generic/mmu_context.h: In function 'activate_mm':
>> include/asm-generic/mmu_context.h:59:2: error: implicit declaration of function 'switch_mm' [-Werror=implicit-function-declaration]
      59 |  switch_mm(prev_mm, next_mm, current);
         |  ^~~~~~~~~
   cc1: some warnings being treated as errors
--
   In file included from ./arch/c6x/include/generated/asm/mmu_context.h:1,
                    from include/linux/mmu_context.h:5,
                    from kernel//sched/sched.h:54,
                    from kernel//sched/rt.c:6:
   include/asm-generic/mmu_context.h: In function 'activate_mm':
>> include/asm-generic/mmu_context.h:59:2: error: implicit declaration of function 'switch_mm' [-Werror=implicit-function-declaration]
      59 |  switch_mm(prev_mm, next_mm, current);
         |  ^~~~~~~~~
   kernel//sched/rt.c: At top level:
   kernel//sched/rt.c:668:6: warning: no previous prototype for 'sched_rt_bandwidth_account' [-Wmissing-prototypes]
     668 | bool sched_rt_bandwidth_account(struct rt_rq *rt_rq)
         |      ^~~~~~~~~~~~~~~~~~~~~~~~~~
   cc1: some warnings being treated as errors

vim +/switch_mm +59 include/asm-generic/mmu_context.h

    49	
    50	/**
    51	 * activate_mm - called after exec switches the current task to a new mm, to switch to it
    52	 * @prev_mm: previous mm of this task
    53	 * @next_mm: new mm
    54	 */
    55	#ifndef activate_mm
    56	static inline void activate_mm(struct mm_struct *prev_mm,
    57				       struct mm_struct *next_mm)
    58	{
  > 59		switch_mm(prev_mm, next_mm, current);
    60	}
    61	#endif
    62	

---
0-DAY CI Kernel Test Service, Intel Corporation
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