CONFIG_USER_RETURN_NOTIFIER (not configurable)

modulename: user-return-notifier.ko

configname: CONFIG_USER_RETURN_NOTIFIER

Linux Kernel Configuration
└─>USER_RETURN_NOTIFIER
In linux kernel since version 2.6.33 (release Date: 2010-02-24)  
Provide a kernel-internal notification when a cpu is about to
switch to user mode.

source code:
kernel/user-return-notifier.c