CONFIG_EMULATED_CMPXCHG is not available for thedefaultarchitecture x86.
Result is shown for architecture sparc

CONFIG_EMULATED_CMPXCHG (not configurable)

configname: CONFIG_EMULATED_CMPXCHG

Linux/SPARC Kernel Configuration
└─>Processor type and features
└─>EMULATED_CMPXCHG
In linux kernel since version 2.6.22 (release Date: 2007-07-08)  
Sparc32 does not have a CAS instruction like sparc64. cmpxchg()
is emulated, and therefore it is not completely atomic.

is selected by
CONFIG_DRM