Hi Dmitry,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on linus/master]
[cannot apply to v5.4-rc2 next-20191011]
[if your patch is applied to the wrong git tree, please drop us a note to help
improve the system. BTW, we also suggest to use '--base' option to specify the
base tree in git format-patch, please see https://stackoverflow.com/a/37406982]

url:    https://github.com/0day-ci/linux/commits/Dmitry-Safonov/kernel-Introduce-Time-Namespace/20191014-075119
config: i386-tinyconfig (attached as .config)
compiler: gcc-7 (Debian 7.4.0-13) 7.4.0
reproduce:
        # save the attached .config to linux build tree
        make ARCH=i386 

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

All errors (new ones prefixed by >>):

   ld: kernel/time/alarmtimer.o: in function `alarmtimer_init':
>> alarmtimer.c:(.init.text+0x26): undefined reference to `posix_get_realtime_timespec'
>> ld: alarmtimer.c:(.init.text+0x44): undefined reference to `posix_get_boottime_timespec'

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