Description of problem:

Kconfig文件存在依赖问题，若不打开CONFIG_PID_NS，编译报错如下


ld: kernel/sysctl.o:(.data+0x24e8): undefined reference to `sysctl_rich_container_enable'
ld: kernel/sysctl.o:(.data+0x2528): undefined reference to `sysctl_rich_container_source'
ld: kernel/sched/cpuacct.o: in function `create_rich_container_reaper.part.0':
cpuacct.c:(.text+0xd94): undefined reference to `sysctl_rich_container_enable'
ld: kernel/sched/cpuacct.o: in function `check_rich_container':
cpuacct.c:(.text+0x18f0): undefined reference to `sysctl_rich_container_enable'
ld: cpuacct.c:(.text+0x1988): undefined reference to `sysctl_rich_container_source'
ld: kernel/sched/cpuacct.o: in function `rich_container_source':
cpuacct.c:(.text+0x1a84): undefined reference to `sysctl_rich_container_source'
ld: kernel/cgroup/cpuset.o: in function `rich_container_get_cpuset_cpus':
cpuset.c:(.text+0x37a7): undefined reference to `sysctl_rich_container_source'
ld: fs/quota/dquot.o: in function `ignore_hardlimit.isra.0':
dquot.c:(.text+0x8fb): undefined reference to `sysctl_rich_container_enable'
ld: fs/proc/array.o: in function `do_task_stat':
array.c:(.text+0x4a6): undefined reference to `sysctl_rich_container_enable'
ld: fs/proc/loadavg.o: in function `loadavg_proc_show':
loadavg.c:(.text+0x21): undefined reference to `sysctl_rich_container_enable'
ld: fs/proc/stat.o: in function `show_stat':
stat.c:(.text+0x11f): undefined reference to `sysctl_rich_container_enable'
ld: fs/proc/uptime.o: in function `uptime_proc_show':
uptime.c:(.text+0x73): undefined reference to `sysctl_rich_container_enable'
ld: drivers/base/cpu.o:cpu.c:(.text+0x382): more undefined references to `sysctl_rich_container_enable' follow
ld: drivers/base/cpu.o: in function `show_cpus_attr':
cpu.c:(.text+0x42b): undefined reference to `sysctl_rich_container_source'
make: *** [Makefile:1189: vmlinux] Error 1