Hi Marcelo,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on tip/sched/core]
[also build test ERROR on tip/master linus/master v5.13 next-20210701]
[cannot apply to hnaz-linux-mm/master tip/core/entry]
[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/Marcelo-Tosatti/optionally-sync-per-CPU-vmstats-counter-on-return-to-userspace/20210702-050826
base:   https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git 031e3bd8986fffe31e1ddbf5264cccfe30c9abd7
config: i386-tinyconfig (attached as .config)
compiler: gcc-9 (Debian 9.3.0-22) 9.3.0
reproduce (this is a W=1 build):
        # https://github.com/0day-ci/linux/commit/b973a70c0670675073265d2cbee70a36bda3273e
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Marcelo-Tosatti/optionally-sync-per-CPU-vmstats-counter-on-return-to-userspace/20210702-050826
        git checkout b973a70c0670675073265d2cbee70a36bda3273e
        # save the attached .config to linux build tree
        mkdir build_dir
        make W=1 O=build_dir ARCH=i386 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 >>):

   ld: kernel/entry/common.o: in function `syscall_exit_to_user_mode_work':
>> common.c:(.text+0x1d8): undefined reference to `vmstat_sync_enabled'
>> ld: common.c:(.text+0x1e1): undefined reference to `__sync_vmstat'
   ld: kernel/entry/common.o: in function `syscall_exit_to_user_mode':
>> common.c:(.noinstr.text+0x71): undefined reference to `vmstat_sync_enabled'
>> ld: common.c:(.noinstr.text+0x7a): undefined reference to `__sync_vmstat'

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